Bio

Bio


Professor Andriacchi's research focuses on the biomechanics of human locomotion and its biomedical applications to artificial joints, sports injury, osteoarthritis, and neuromuscular disorders. He is the author of more than 200 original papers, more than 500 abstracts and numerous book chapters and is an active member of several national and international societies. He is a past member of the Editorial Board for the Journal of Biomechanics and serves on the Board of Associate Editors for the Journal of Orthopedic Research. Among his honors, Dr. Andriacchi has received the Kappa Delta Award, the highest award of the Orthopedic Research Society and the Borelli Award, the highest award of the American Society of Biomechanics. He is Past President of the American Society of Biomechanics and past Secretary-Treasurer for the Orthopedic Research Society and a former member of its Board of Directors.

Academic Appointments


Honors & Awards


  • Life-time Achievement Award, International Society for Technology in Arthroplasty (2013)
  • Contributions to Osteoarthritis Research, Arthritis Foundation (2012)
  • H.R. Lissner Medal, American Society of Mechanical Engineers (2009)
  • Lifetime Achievement Award, San Francisco Bay Area Knee Society (2008)
  • Fellow of American Society of Mechanical Engineers, American Society of Mechanical Engineers (2007)
  • Borelli Award, American Society of Biomechanics (2004)
  • Kappa Delta Award, Orthopedic Research Society (2004)
  • Mark Coventry Award, Knee Society (2002)
  • Excellence in Research Award, American Orthopaedic Society for Sports Medicine (1984)
  • Kappa Delta Award, Orhopedic Research Society (1983)

Professional Education


  • Ph.D., Unversity of Illinois Chicago, Mechanical Engineering (1974)

Research & Scholarship

Current Research and Scholarly Interests


The main focus of the research conducted in Professor Andriacchi’s Biomotion Laboratory is to apply the study of normal and pathological human movement to the evaluation and treatment of musculoskeletal disease and injury. The Laboratory provides unique information on the relationship between the in vivo pathomechanics of human movement and the mechanisms that influence the initiation and progression of musculoskeletal disease and injury. As such, the Laboratory intergrates information from collaborative studies that conduct animal and/or in vitro testing by providing the in vivo perspective on the problem. Specifically, the Laboratory has identified unique ambulatory conditions that are associated with the development of premature osteoarthritis following joint trauma. The Laboratory is using this information as an objective tool to evaluate the efficacy of specific treatments for modifying ambulatory patterns that lead to post-trauma osteoarthritis. Similarly, the association between obesity and premature osteoarthritis is being studied to evaluate the interactions between ambulatory changes , biological changes (from serum biomarkers) and structural changes to cartilage (from MRI) that converge to make obesity the main risk factor for developing osteoarthritis.

This work has had direct translational results producing an inexpensive load modifying intervention in the form of a shoe that has been shown to reduce knee pain in patients with medial compartment osteoarthritis. There is also a major program to develop prevention strategies for reducing the risk for anterior cruciate ligament injury, a common sports injury to the knee. Improved methods for assessing morphological cartilage changes from MR images have been developed and applied to establishing a relationship between mechanical loading during walking and cartilage thickness. Finally, the Laboratory has been a leader in the development of improved methods for the measurement and analysis of human movement. One such improvement is the creation and development of a markerless motion capture system giving the researchers the capacity to analyze human movement without placing markers on the subject.

Clinical Trials


  • The Design and Evaluation of an Active Intervention for the Prevention of Non-contact ACL Injury Not Recruiting

    The overall goal of this project is to reduce the risk for anterior cruciate ligament injuries by designing a targeted intervention that will alter the known kinematic and kinetic risk factors associated with ACL injuries. This study will address the following specific aims: 1) To optimize a wearable, targeted, active training feedback device to reduce the risk of ACL injury among healthy subjects by inducing patterns of movement that alter the known kinematic and kinetic risk factors associated with ACL injuries. 2) To evaluate the efficacy of the active device and determine if the device reduces the risk of ACL injury among healthy subjects by effectively inducing patterns of movement that alter the known kinematic and kinetic risk factors associated with ACL injuries.

    Stanford is currently not accepting patients for this trial. For more information, please contact Ariel Dowling, PhD, 908-229-8208.

    View full details

Teaching

2013-14 Courses


Publications

Journal Articles


  • OSTEOARTHRITIS Probing knee OA as a system responding to a stimulus NATURE REVIEWS RHEUMATOLOGY Andriacchi, T. P. 2012; 8 (7): 371-372

    View details for DOI 10.1038/nrrheum.2012.59

    View details for Web of Science ID 000305969900001

    View details for PubMedID 22526027

  • Effect of variable-stiffness walking shoes on knee adduction moment, pain, and function in subjects with medial compartment knee osteoarthritis after 1 year JOURNAL OF ORTHOPAEDIC RESEARCH Erhart-Hledik, J. C., Elspas, B., Giori, N. J., Andriacchi, T. P. 2012; 30 (4): 514-521

    Abstract

    This study investigated the load-modifying and clinical efficacy of variable-stiffness shoes after 12 months in subjects with medial compartment knee osteoarthritis. Subjects who completed a prior 6-month study were asked to wear their assigned constant-stiffness control or variable-stiffness intervention shoes during the remainder of the study. Changes in peak knee adduction moment, total Western Ontario and McMaster Universities (WOMAC), and WOMAC pain scores were assessed. Seventy-nine subjects were enrolled, and 55 completed the trial. Using an intention-to-treat analysis, the variable-stiffness shoes reduced the within-day peak knee adduction moment (-5.5%, p?

    View details for DOI 10.1002/jor.21563

    View details for Web of Science ID 000299935900002

    View details for PubMedID 21953877

  • Differences in tibial rotation during walking in ACL reconstructed and healthy contralateral knees JOURNAL OF BIOMECHANICS Scanlan, S. F., Chaudhari, A. M., Dyrby, C. O., Andriacchi, T. P. 2010; 43 (9): 1817-1822

    Abstract

    This study tested the hypotheses that in patients with a successful anterior cruciate ligament (ACL) reconstruction, the internal-external rotation, varus-valgus, and knee flexion position of reconstructed knees would be different from uninjured contralateral knees during walking. Twenty-six subjects with unilateral ACL reconstructions (avg 31 years, 1.7 m, 68 kg, 15 female, 24 months past reconstruction) and no other history of serious lower limb injury walked at a self-selected speed in the gait laboratory, with the uninjured contralateral knee as a matched control. Kinematic measurements of tibiofemoral motion were made using a previously-described point-cluster technique. Repeated-measures ANOVA (alpha=0.017) was used to compare ACL-reconstructed knees to their contralateral knees at four distinct points during the stance phase of walking. An offset towards external tibial rotation in ACL-reconstructed knees was maintained over all time points (95%CI 2.3+/-1.3 degrees ). Twenty-two out of twenty-six individuals experienced an average external tibial rotation offset throughout stance phase. Varus-valgus rotation and knee flexion were not significantly different between reconstructed and contralateral knees. These findings show that differences in tibial rotation during walking exist in ACL reconstructed knees compared to healthy contralateral knees, providing a potential explanation why these patients are at higher risk of knee osteoarthritis in the long-term.

    View details for DOI 10.1016/j.jbiomech.2010.02.010

    View details for Web of Science ID 000279468500024

    View details for PubMedID 20181339

  • Gait Mechanics Influence Healthy Cartilage Morphology and Osteoarthritis of the Knee JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Andriacchi, T. P., Koo, S., Scanlan, S. F. 2009; 91A: 95-101

    Abstract

    The response of healthy and diseased cartilage of the knee to the mechanics of walking is examined, with the goal of providing insight into the relationship between the kinematics and kinetics of the knee during walking and the maintenance of cartilage health. The combination of information from three-dimensional thickness models of cartilage derived from magnetic resonance imaging and the analysis of the interaction between load at the knee and kinematic changes during walking associated with loss of the anterior cruciate ligament demonstrated the importance of considering walking mechanics as an important factor in the initiation and progression of osteoarthritis. In particular, this material suggests that knee cartilage becomes conditioned to loading and to the large number of repetitive cycles of loading that occur during walking and that healthy cartilage homeostasis is maintained as long as there are no changes to the normal patterns of locomotion, the structure of the knee joint, or cartilage biology. Thus, there is the potential for a degenerative pathway to be initiated when a condition such as anterior cruciate ligament injury causes the repetitive loading during walking to shift to a new location. The sensitivity of cartilage to the kinematic changes is illustrated with the anterior cruciate ligament-deficient knee and the regional variations in cartilage morphology. The material presented here supports the conclusion that individual variations in the range of loading and kinematics at the knee during walking can have a profound influence on the initiation and progression of osteoarthritis of the knee.

    View details for DOI 10.2106/JBJS.H.01408

    View details for Web of Science ID 000263243000023

    View details for PubMedID 19182033

  • Knee kinematics, cartilage morphology, and osteoarthritis after ACL injury MEDICINE AND SCIENCE IN SPORTS AND EXERCISE Chaudhari, A. M., Briant, P. L., Bevill, S. L., Koo, S., Andriacchi, T. P. 2008; 40 (2): 215-222

    Abstract

    This review examines a mechanism for the initiation of osteoarthritis after anterior cruciate ligament (ACL) injury by considering the relationship between reported ambulatory changes after ACL injury, cartilage adaptation to load, and the association between cartilage loads during walking and regional variations in cartilage structure and biology. Taken together, these observations suggest that cartilage degeneration after ACL injury could be caused by a kinematic gait change that shifts ambulatory loading applied to cartilage. Such a shift may cause regions of cartilage to become newly loaded, be subjected to altered levels of compression and tension, or become unloaded. The metabolic sensitivity of chondrocytes to such changes in their mechanical environment, combined with the low adaptation potential of mature cartilage, could lead to cartilage degeneration and premature osteoarthritis after ACL injury. This proposed mechanism demonstrates the value of using the ACL injury model to understand the relationship between mechanics and biology, as well as helping to explain the importance of restoring normal ambulatory kinematics after ACL injury to avoid premature osteoarthritis.

    View details for DOI 10.1249/mss.0b013e31815cbb0e

    View details for Web of Science ID 000252608300005

    View details for PubMedID 18202582

  • A framework for the in vivo pathomechanics of osteoarthritis at the knee ANNALS OF BIOMEDICAL ENGINEERING Andriacchi, T. P., Mundermann, A., Smith, R. L., Alexander, E. J., Dyrby, C. O., Koo, S. 2004; 32 (3): 447-457

    Abstract

    The in vivo pathomechanics of osteoarthritis (OA) at the knee is described in a framework that is based on an analysis of studies describing assays of biomarkers, cartilage morphology, and human function (gait analysis). The framework is divided into an Initiation Phase and a Progression Phase. The Initiation Phase is associated with kinematic changes that shift load bearing to infrequently loaded regions of the cartilage that cannot accommodate the loads. The Progression Phase is defined following cartilage breakdown. During the Progression Phase, the disease progresses more rapidly with increased load. While this framework was developed from an analysis of in vivo pathomechanics, it also explains how the convergence of biological, morphological, and neuromuscular changes to the musculoskeletal system during aging or during menopause lead to the increased rate of idiopathic OA with aging. Understanding the in vivo response of articular cartilage to its physical environment requires an integrated view of the problem that considers functional, anatomical, and biological interactions. The integrated in vivo framework presented here will be helpful for the interpretation of laboratory experiments as well as for the development of new methods for the evaluation of OA at the knee.

    View details for Web of Science ID 000222465100016

    View details for PubMedID 15095819

  • Biomechanical analysis of three tennis serve types using a markerless system BRITISH JOURNAL OF SPORTS MEDICINE Abrams, G. D., Harris, A. H., Andriacchi, T. P., Safran, M. R. 2014; 48 (4)

    Abstract

    PURPOSE: The tennis serve is commonly associated with musculoskeletal injury. Advanced players are able to hit multiple serve types with different types of spin. No investigation has characterised the kinematics of all three serve types for the upper extremity and back. METHODS: Seven NCAA Division I male tennis players performed three successful flat, kick and slice serves. Serves were recorded using an eight camera markerless motion capture system. Laser scanning was utilised to accurately collect body dimensions and data were computed using inverse kinematic methods. RESULTS: There was no significant difference in maximum back extension angle for the flat, kick or slice serves. The kick serve had a higher force magnitude at the back than the flat and slice as well as larger posteriorly directed shoulder forces. The flat serve had significantly greater maximum shoulder internal rotation velocity versus the slice serve. Force and torque magnitudes at the elbow and wrist were not significantly different between the serves. CONCLUSIONS: The kick serve places higher physical demands on the back and shoulder while the slice serve demonstrated lower overall kinetic forces. This information may have injury prevention and rehabilitation implications.

    View details for DOI 10.1136/bjsports-2012-091371

    View details for Web of Science ID 000331185400013

    View details for PubMedID 22936411

  • Repeatability of gait analysis for measuring knee osteoarthritis pain in patients with severe chronic pain. Journal of orthopaedic research Asay, J. L., Boyer, K. A., Andriacchi, T. P. 2013; 31 (7): 1007-1012

    Abstract

    Gait measures are receiving increased attention in the evaluation of patients with knee osteoarthritis (OA). Yet, there remains a need to assess variability of gait analysis in patients with knee osteoarthritis over time and how pain affects variation in these gait parameters. The purpose of this study was to determine if important gait parameters, such as the knee adduction moment, knee flexion moment, peak vertical ground reaction force, and speed, were repeatable in patients with mild-to-moderate knee OA over a trial period of 12 weeks. Six patients were enrolled in this cross-over study design after meeting strict inclusion criteria. Gait tests were conducted three times at 4 week intervals and once after the placebo arm of a randomized treatment sequence; each gait test followed a 2-week period of receiving a placebo for a pain modifying drug. Repeatability for each gait variable was found using intraclass correlation coefficients (ICC) with a two-way random model. This study found that the knee adduction moment was repeatable throughout the four gait tests. However, normalized peak vertical ground reaction force and knee flexion moment were not as repeatable, varying with pain. This suggests that these gait outcomes could offer a more objective way to measure a patient's level of pain. © 2012 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1007-1012, 2013.

    View details for DOI 10.1002/jor.22228

    View details for PubMedID 23508626

  • The relationship between peak knee extension at heel-strike of walking and the location of thickest femoral cartilage in ACL reconstructed and healthy contralateral knees JOURNAL OF BIOMECHANICS Scanlan, S. F., Favre, J., Andriacchi, T. P. 2013; 46 (5): 849-854

    Abstract

    Reports that knee cartilage health is sensitive to kinematic changes, combined with reports of extension loss following ACL reconstruction, underscores the importance of restoring ambulatory knee extension in the context of preventing premature osteoarthritis. The purpose of this study was to test the relationship between individual variations in peak knee extension at heel-strike of walking and the anterior-posterior location of thickest cartilage in the medial and lateral femoral condyles of healthy contralateral and ACL reconstructed knees. In vivo gait analysis and knee MR images were collected from 29 subjects approximately 2 years after unilateral ACL reconstruction. Knee extension was measured at heel-strike of walking and 3-D femoral cartilage thickness models were reconstructed from MR images. The ACL reconstructed knees had significantly reduced knee extension (-1.5±4.2°) relative to the contralateral knees (-4.6±3.4°) at heel-strike of walking but did not have side-to-side differences in the anterior-posterior location or magnitude of thickest medial and lateral femoral cartilage. The anterior-posterior location of the thickest medial femoral cartilage was correlated with knee extension at heel-strike in both the healthy contralateral (R(2)=0.356, p<0.001) and reconstructed (R(2)=0.234, p=0.008) knees. These results suggest that ACL reconstruction can impair terminal extension at periods of ambulatory loading known to be related to cartilage morphology in healthy joints. The fact that the femoral cartilage thickness distribution had not changed at 2 years post-op, even in the subset of subjects with extension loss, suggests that loads may be shifted to thinner cartilage regions, which could have important implications on long-term joint health.

    View details for DOI 10.1016/j.jbiomech.2012.12.026

    View details for Web of Science ID 000316829700001

    View details for PubMedID 23375789

  • Valgus Alignment and Lateral Compartment Knee Osteoarthritis: A Biomechanical Paradox or New Insight Into Knee Osteoarthritis? ARTHRITIS AND RHEUMATISM Andriacchi, T. P. 2013; 65 (2): 310-313

    View details for DOI 10.1002/art.37724

    View details for Web of Science ID 000314169400004

    View details for PubMedID 23203607

  • Three-dimensional knee moments of ACL reconstructed and control subjects during gait, stair ascent, and stair descent JOURNAL OF BIOMECHANICS Zabala, M. E., Favre, J., Scanlan, S. F., Donahue, J., Andriacchi, T. P. 2013; 46 (3): 515-520

    Abstract

    Changes in knee mechanics following anterior cruciate ligament reconstruction (ACLR) have been implicated as a contributor to the development of premature osteoarthritis (OA). However, changes in ambulatory loading in this population have not been well documented. While the magnitude of the external knee moment vector is a major factor in loading at the knee, there is not a comprehensive understanding of the changes in the individual components of the vector following ACL reconstruction. The purpose of this study was to test for differences in the three components of the external knee moment during walking and stair locomotion between ACLR, contralateral and healthy control knees. Forty-five ACLR and 45 healthy control subjects were tested during walking, stair ascent and descent. ACLR knees had a lower first peak adduction moment than contralateral knees during all three activities. Similarly, additional cases of significant differences between ACLR and contralateral knees consisted of lower peak moments for the ACLR than the contralateral knees. These differences were due to both ACLR and contralateral knees as the ACLR knees indicated lower and the contralateral knees greater peak moments compared to healthy control knees. The results suggest a compensatory change involving greater loading in the contralateral knee, perhaps due to lower loading of the ACLR knee. Further, lower knee moments of the ACLR knee suggest that increased joint loading may not be the initiating factor in the development of OA following ACL reconstruction; but rather previous described kinematic or biological changes might initiate the pathway to knee OA.

    View details for DOI 10.1016/j.jbiomech.2012.10.010

    View details for Web of Science ID 000315317100013

    View details for PubMedID 23141637

  • The in vivo relationship between anterior neutral tibial position and loss of knee extension after transtibial ACL reconstruction. The Knee Scanlan, S. F., Donahue, J. P., Andriacchi, T. P. 2013

    Abstract

    Restoration of anterior tibial stability while avoiding knee extension deficit are a common goal of anterior cruciate ligament (ACL) reconstruction. However, achieving this goal can be challenging. The purpose of this study was to determine whether side-to-side differences in anterior tibial neutral position and laxity are correlated with knee extension deficit in subjects 2years after ACL reconstruction.In the reconstructed and contralateral knees of 29 subjects with transtibial reconstruction, anterior tibiofemoral neutral position was measured with MRI and three-dimensional modeling techniques; terminal knee extension at heel strike of walking and during a seated knee extension were measured via gait analysis; and anterior laxity was measured using the KT-1000.Knees that approached normal anterior stability and anterior tibial position had increased extension deficit relative to the contralateral knee. On average the reconstructed knee had significantly less (2.1±4.4°) extension during active extension and during heel strike of walking (3.0±4.3º), with increased anterior neutral tibial position (2.5±1.7mm) and anterior laxity (1.8±1.0mm). There was a significant correlation between side-to-side difference in anterior neutral tibial position with both measures of knee extension (walking, r=-0.711, p<0.001); active knee extension, r=-0.544, p=0.002).The results indicate a relationship between the loss of active knee extension and a change in anterior neutral tibial position following non-anatomic transtibial ACL reconstruction. Given the increasing evidence of a link between altered kinematics and premature osteoarthritis, these findings provide important information to improve our understanding of in vivo knee function after ACL reconstruction.

    View details for PubMedID 23830645

  • A relationship between mechanically-induced changes in serum cartilage oligomeric matrix protein (COMP) and changes in cartilage thickness after 5 years OSTEOARTHRITIS AND CARTILAGE Erhart-Hledik, J. C., Favre, J., Asay, J. L., Smith, R. L., Giori, N. J., Muendermann, A., Andriacchi, T. P. 2012; 20 (11): 1309-1315

    Abstract

    To evaluate the hypothesis that a mechanical stimulus (30-min walk) will produce a change in serum concentrations of cartilage oligomeric matrix protein (COMP) that is associated with cartilage thickness changes on magnetic resonance imaging (MRI).Serum COMP concentrations were measured by enzyme-linked immunosorbent assay in 17 patients (11 females, age: 59.0±9.2 years) with medial compartment knee osteoarthritis (OA) at study entry immediately before, immediately after, 3.5 h, and 5.5 h after a 30-min walking activity. Cartilage thickness changes in the medial femur and medial tibia were determined from MR images taken at study entry and at 5-year follow-up. Relationships between changes in cartilage thickness and COMP levels, with post-activity concentrations expressed as a percentage of pre-activity levels, were assessed by the calculation of Pearson correlation coefficients and by multiple linear regression analysis, with adjustments for age, sex, and body mass index (BMI).Changes in COMP levels 3.5 h and 5.5 h post-activity were correlated with changes in cartilage thickness in the medial femur and tibia at the 5-year follow-up. The results were strengthened after analyses were adjusted for age, sex, and BMI. Neither baseline pre-activity COMP levels nor changes in COMP levels immediately post-activity were correlated with cartilage thickness changes.The results of this study support the hypothesis that a change in COMP concentration induced by a mechanical stimulus is associated with cartilage thinning at 5 years. Mechanically-induced changes in mechano-sensitive biomarkers should be further explored in the context of stimulus-response models to improve the ability to assess OA progression.

    View details for DOI 10.1016/j.joca.2012.07.018

    View details for Web of Science ID 000309853400013

  • Characterization of Thigh and Shank Segment Angular Velocity During Jump Landing Tasks Commonly Used to Evaluate Risk for ACL Injury JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Dowling, A. V., Favre, J., Andriacchi, T. P. 2012; 134 (9)

    Abstract

    The dynamic movements associated with anterior cruciate ligament (ACL) injury during jump landing suggest that limb segment angular velocity can provide important information for understanding the conditions that lead to an injury. Angular velocity measures could provide a quick and simple method of assessing injury risk without the constraints of a laboratory. The objective of this study was to assess the inter-subject variations and the sensitivity of the thigh and shank segment angular velocity in order to determine if these measures could be used to characterize jump landing mechanisms. Additionally, this study tested the correlation between angular velocity and the knee abduction moment. Thirty-six healthy participants (18 male) performed drop jumps with bilateral and unilateral landing. Thigh and shank angular velocities were measured by a wearable inertial-based system, and external knee moments were measured using a marker-based system. Discrete parameters were extracted from the data and compared between systems. For both jumping tasks, the angular velocity curves were well defined movement patterns with high inter-subject similarity in the sagittal plane and moderate to good similarity in the coronal and transverse planes. The angular velocity parameters were also able to detect differences between the two jumping tasks that were consistent across subjects. Furthermore, the coronal angular velocities were significantly correlated with the knee abduction moment (R of 0.28-0.51), which is a strong indicator of ACL injury risk. This study suggested that the thigh and shank angular velocities, which describe the angular dynamics of the movement, should be considered in future studies about ACL injury mechanisms.

    View details for DOI 10.1115/1.4007178

    View details for Web of Science ID 000308415200008

    View details for PubMedID 22938373

  • Sensitivity of gait parameters to the effects of anti-inflammatory and opioid treatments in knee osteoarthritis patients JOURNAL OF ORTHOPAEDIC RESEARCH Boyer, K. A., Angst, M. S., Asay, J., Giori, N. J., Andriacchi, T. P. 2012; 30 (7): 1118-1124

    Abstract

    The study aim was to address the need for objective markers of pain-modifying interventions by testing the hypothesis that selective gait measures of knee joint loading can distinguish differences between non-steroidal anti-inflammatory (NSAID), analgesic treatment (opioid-receptor agonist), and placebo in patients medial knee osteoarthritis (OA). A randomized, single-blind washout, double-blind treatment, double-dummy cross-over trial using three treatment arms placebo, opioid (Oxycodone), and NSAID (Celecoxib) in medial compartment knee OA patients. Six patients with Kellgren-Lawrence radiographic severity grades of 2 or 3 completed six testing sessions (gait and pain assessment) at 2-week intervals. A significant increase was found in the knee total reaction moment and vertical ground reaction force (GRF) for Celecoxib compared to placebo (p=0.005, p=0.003), but not for Oxycodone compared to placebo (p=0.20, p=0.27) treatments. Walking speed was significantly higher for the Celecoxib and Oxycodone compared to placebo treatment (p=0.041 and p=0.031, respectively). Self-reported function (WOMAC scores) was not different among treatments (p>0.05). The changes in total reaction moments and GRFs for only the NSAID suggest that greater increases in joint loading occurs when joint inflammation is treated in addition to pain. The total knee reaction moment, representing the magnitude of the extrinsic moment, appears to be a sensitive marker, more so than self-reported metrics, for evaluating knee OA treatment effects.

    View details for DOI 10.1002/jor.22037

    View details for Web of Science ID 000303810000016

    View details for PubMedID 22179861

  • Variations in the three-dimensional location and orientation of the ACL in healthy subjects relative to patients after transtibial ACL reconstruction JOURNAL OF ORTHOPAEDIC RESEARCH Scanlan, S. F., Lai, J., Donahue, J. P., Andriacchi, T. P. 2012; 30 (6): 910-918

    Abstract

    Recent reports have indicated that anatomical placement of the anterior cruciate ligament (ACL) graft is an important factor for restoration of joint function following ACL reconstruction. The objective of this study was to address a need for a better understanding of anatomical variations in ACL position and orientation within the joint. Specifically, variations in the ACL anatomy were assessed by testing for side-to-side ACL footprint location symmetry in a healthy population relative to the operative and contralateral knee in a patient population after traditional transtibial single-bundle ACL reconstruction. MRI and three-dimensional modeling techniques were used to determine the in vivo tibiofemoral ACL footprint centers and the resulting ACL orientations in both knees of 30 healthy subjects and 30 subjects after transtibial ACL reconstruction. While there were substantial inter-subject variations in ACL anatomy, the side-to-side RMS differences in the ACL footprint center were 1.20 and 1.34 mm for the femur and tibia, respectively, for the healthy subjects and no clinically meaningful intra-subject differences were measured. However, there were large intra-subject side-to-side differences after transtibial ACL reconstruction, with ACL grafts placed 5.63 and 7.64 mm from the center of the contralateral femoral and tibial ACL footprint centers, respectively. Grafts were placed more medial, anterior, and superior on the femur and more posterior on the tibia; producing grafts that were more vertical in the sagittal and coronal planes. Given the large variation among subjects, these findings advocate the use of the contralateral ACL morphology for retrospectively evaluating patient-specific anatomic graft placement.

    View details for DOI 10.1002/jor.22011

    View details for Web of Science ID 000302466700010

    View details for PubMedID 22105556

  • Kinematic adaptations to a variable stiffness shoe: Mechanisms for reducing joint loading JOURNAL OF BIOMECHANICS Boyer, K. A., Federolf, P., Lin, C., Nigg, B. M., Andriacchi, T. P. 2012; 45 (9): 1619-1624

    Abstract

    A recently described variable-stiffness shoe has been shown to reduce the adduction moment and pain in patients with medial-compartment knee osteoarthritis. The mechanism associated with how this device modifies overall gait patterns to reduce the adduction moment is not well understood. Yet this information is important for applying load modifying intervention for the treatment of knee osteoarthritis. A principal component analysis (PCA) was used to test the hypothesis that there are differences in the frontal plane kinematics that are correlated with differences in the ground reaction forces (GRFs) and center of pressure (COP) for a variable-stiffness compared to a constant-stiffness control shoe. Eleven healthy adults were tested in a constant-stiffness control shoe and a variable-stiffness shoe while walking at self-selected speeds. The PCA was performed on trial vectors consisting of all kinematic, GRF and COP data. The projection of trial vectors onto the linear combination of four PCs showed there were significant differences between shoes. The interpretation of the PCs indicated an increase in the ankle eversion, knee abduction and adduction, decreases in the hip adduction and pelvic obliquity angles and reduced excursion of both the COP and peak medial-lateral GRFs for the variable-stiffness compared to the control shoe. The variable-stiffness shoe produced a unique dynamic change in the frontal plane motion of the ankle, hip and pelvis that contributed to changes in the GRF and COP and thus reduced the adduction moment at a critical instant during gait suggesting a different mechanism that was seen with fixed interventions (e.g. wedges).

    View details for DOI 10.1016/j.jbiomech.2012.04.010

    View details for Web of Science ID 000305493000010

    View details for PubMedID 22541945

  • Inertial Sensor-Based Feedback Can Reduce Key Risk Metrics for Anterior Cruciate Ligament Injury During Jump Landings AMERICAN JOURNAL OF SPORTS MEDICINE Dowling, A. V., Favre, J., Andriacchi, T. P. 2012; 40 (5): 1075-1083

    Abstract

    The incidence of anterior cruciate ligament (ACL) injury can be decreased through the use of intervention programs. However, the success of these programs is dependent on access to a skilled trainer who provides feedback; as such, these programs would benefit from a simple device with the capacity to provide high-quality feedback.Feedback based on kinematic measurements from a simple inertial sensor-based system can be used to modify key ACL injury risk metrics (knee flexion angle, trunk lean, knee abduction moment) during jump landing.Controlled laboratory study.Seventeen subjects (7 male) were tested during drop jump tasks. Their movements were measured simultaneously with inertial, optoelectronic, and force platform systems. Feedback provided to the subjects was based only on measurements from the inertial sensor-based system (knee flexion angle, trunk lean, and thigh coronal velocity). The subjects conducted a baseline session (without landing instructions), then a training session (with immediate feedback), and finally an evaluation session (without feedback). The baseline and evaluation sessions were then tested for changes in the key risk metrics.The subjects increased their knee flexion angle (16.2°) and trunk lean (17.4°) after the training. They also altered their thigh coronal angular velocity by 29.4 deg/s and reduced their knee abduction moment by 0.5 %BW·Ht. There was a significant correlation (R (2) = 0.55) between the change in thigh coronal angular velocity and the change in knee abduction moment.Subjects reduced key risk metrics for ACL injury after training with the system, suggesting the potential benefit of instrumented feedback for interventional training.Interventional training for reducing the risk of ACL injury could be improved with a simple device that provides immediate feedback.

    View details for DOI 10.1177/0363546512437529

    View details for Web of Science ID 000303323900017

    View details for PubMedID 22459239

  • The role of physical activity in changes in walking mechanics with age GAIT & POSTURE Boyer, K. A., Andriacchi, T. P., Beaupre, G. S. 2012; 36 (1): 149-153

    Abstract

    While age-related declines in walking mechanics have been documented, it remains unclear if changes in walking mechanics with age occur as a natural consequence of aging and to what extent these changes are related to a reduction in fitness and physical activity with aging. The study aim was to determine if the walking mechanics of an older (>50) yet highly active population are different from a younger population (<40). Gait mechanics data for 79 middle-aged (50-64 yrs) and 54 older (65-80 yrs) individuals with ? 7500 steps/day, based on a 7 day activity monitoring history, and 33 younger adults (ages 18-40) were collected. The older subjects did not reduce self-selected walking speed relative to the younger subjects. However, the walking speed was maintained by increasing cadence while reducing stride-length for middle-aged and older subjects. Middle-aged and older adults had less ankle dorsi-flexion landing at heel-strike and older adults also had less plantar flexion at toe-off. Small decreases in the ankle dorsi-flexion moments (p=0.019, p=0.008) and increases in the hip extension moments (p=0.004, p=0.005) were found for two normalized walking speeds for the middle-aged and older adults compared to the young adults. These results provide quantitative evidence that increased activity with aging can mitigate declines in walking performance and mechanics with age. The high volume of walking activity in the older subjects did not fully prevent changes in gait mechanics, but may have minimized the magnitude of age-related changes on ambulatory function relative to other reports of older inactive subjects.

    View details for DOI 10.1016/j.gaitpost.2012.02.007

    View details for Web of Science ID 000306449100027

    View details for PubMedID 22445586

  • Direct comparison of measured and calculated total knee replacement force envelopes during walking in the presence of normal and abnormal gait patterns JOURNAL OF BIOMECHANICS Lundberg, H. J., Foucher, K. C., Andriacchi, T. P., Wimmer, M. A. 2012; 45 (6): 990-996

    Abstract

    Knee joint forces measured from instrumented implants provide important information for testing the validity of computational models that predict knee joint forces. The purpose of this study was to validate a parametric numerical model for predicting knee joint contact forces against measurements from four subjects with instrumented TKRs during the stance phase of gait. Model sensitivity to abnormal gait patterns was also investigated. The results demonstrated good agreement for three subjects with relatively normal gait patterns, where the difference between the mean measured and calculated forces ranged from 0.05 to 0.45 body weights, and the envelopes of measured and calculated forces (from three walking trials) overlapped. The fourth subject, who had a "quadriceps avoidance" external moment pattern, initially had little overlap between the measured and calculated force envelopes. When additional constraints were added, tailored to the subject's gait pattern, the model predictions improved to complete force envelope overlap. Coefficient of multiple determination analysis indicated that the shape of the measured and calculated force waveforms were similar for all subjects (adjusted coefficient of multiple correlation values between 0.88 and 0.92). The parametric model was accurate in predicting both the magnitude and waveform of the contact force, and the accuracy of model predictions was affected by deviations from normal gait patterns. Equally important, the envelope of forces generated by the range of solutions substantially overlapped with the corresponding measured envelope from multiple gait trials for a given subject, suggesting that the variable strategic processes of in vivo force generation are covered by the solution range of this parametric model.

    View details for DOI 10.1016/j.jbiomech.2012.01.015

    View details for Web of Science ID 000302980600013

    View details for PubMedID 22284431

  • Computational modeling of bone density profiles in response to gait: a subject-specific approach BIOMECHANICS AND MODELING IN MECHANOBIOLOGY Pang, H., Shiwalkar, A. P., Madormo, C. M., Taylor, R. E., Andriacchi, T. P., Kuhl, E. 2012; 11 (3-4): 379-390

    Abstract

    The goal of this study is to explore the potential of computational growth models to predict bone density profiles in the proximal tibia in response to gait-induced loading. From a modeling point of view, we design a finite element-based computational algorithm using the theory of open system thermodynamics. In this algorithm, the biological problem, the balance of mass, is solved locally on the integration point level, while the mechanical problem, the balance of linear momentum, is solved globally on the node point level. Specifically, the local bone mineral density is treated as an internal variable, which is allowed to change in response to mechanical loading. From an experimental point of view, we perform a subject-specific gait analysis to identify the relevant forces during walking using an inverse dynamics approach. These forces are directly applied as loads in the finite element simulation. To validate the model, we take a Dual-Energy X-ray Absorptiometry scan of the subject's right knee from which we create a geometric model of the proximal tibia. For qualitative validation, we compare the computationally predicted density profiles to the bone mineral density extracted from this scan. For quantitative validation, we adopt the region of interest method and determine the density values at fourteen discrete locations using standard and custom-designed image analysis tools. Qualitatively, our two- and three-dimensional density predictions are in excellent agreement with the experimental measurements. Quantitatively, errors are less than 3% for the two-dimensional analysis and less than 10% for the three-dimensional analysis. The proposed approach has the potential to ultimately improve the long-term success of possible treatment options for chronic diseases such as osteoarthritis on a patient-specific basis by accurately addressing the complex interactions between ambulatory loads and tissue changes.

    View details for DOI 10.1007/s10237-011-0318-y

    View details for Web of Science ID 000300518000008

    View details for PubMedID 21604146

  • A neural network model to predict knee adduction moment during walking based on ground reaction force and anthropometric measurements JOURNAL OF BIOMECHANICS Favre, J., Hayoz, M., Erhart-Hledik, J. C., Andriacchi, T. P. 2012; 45 (4): 692-698

    Abstract

    The external knee adduction moment (KAM) is a major variable for the evaluation of knee loading during walking, specifically in patients with knee osteoarthritis. However, assessment of the KAM is limited to locations where full motion laboratories are available. The purpose of this study was to develop and test a simple method to predict the KAM using only force plate and anthropometric measurements. Three groups of 28 knees (asymptomatic, mild osteoarthritis, and severe osteoarthritis) were studied. Walking trials were collected at different speeds using a motion capture system and a force plate. The reference KAM was calculated by inverse dynamics. For the prediction, inter-subject artificial neural networks were designed using 11 inputs coming from the ground reaction force and the mechanical axis alignment. The predicted KAM curves were similar to the reference curves with median mean absolute deviation (MAD) of 0.36%BW*Ht and median correlation coefficient of 0.966 over 756 individual trials. When comparing mean group curves, the median MAD was 0.09%BW*Ht and the median correlation coefficient 0.998. The peak values and the angular impulses extracted from the predicted and reference curves were significantly correlated, and the same significant differences were obtained among the three groups when the predicted or when the reference curves were used for 95% of the comparisons. In conclusion, this study demonstrated that a simple method using a generic artificial neural network can predict the KAM curve during walking with a high level of significance and provides a practical option for a broader evaluation of the KAM.

    View details for DOI 10.1016/j.jbiomech.2011.11.057

    View details for Web of Science ID 000301748800011

    View details for PubMedID 22257888

  • VALGUS KNEE ALIGNMENT, NOT STEP WIDTH OR TOE-OUT CAUSE REDUCED KNEE ADDUCTION MOMENT IN THE HEALTHY OBESE PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B Blazek, K., Asay, J., Erhart-Hledik, J., Andriacchi, T. 2012: 235-236
  • Amplitude and Phasing of Trunk Motion is Critical for the Efficacy of Gait Training Aimed at Reducing Ambulatory Loads at the Knee JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Muendermann, A., Muendermann, L., Andriacchi, T. P. 2012; 134 (1)

    View details for DOI 10.1115/1.4005540

    View details for Web of Science ID 000302582100010

  • Response to 'Plasma proteins present in osteoarthritic synovial fluid can stimulate cytokine production via Toll-like receptor 4' - authors' reply. Arthritis research & therapy Sohn, D. H., Sokolove, J., Sharpe, O., Erhart, J. C., Chandra, P. E., Lahey, L. J., Lindstrom, T. M., Hwang, I., Boyer, K. A., Andriacchi, T. P., Robinson, W. H. 2012; 14 (5): 406

    View details for PubMedID 22979902

  • Plasma proteins present in osteoarthritic synovial fluid can stimulate cytokine production via Toll-like receptor 4 ARTHRITIS RESEARCH & THERAPY Sohn, D. H., Sokolove, J., Sharpe, O., Erhart, J. C., Chandra, P. E., Lahey, L. J., Lindstrom, T. M., Hwang, I., Boyer, K. A., Andriacchi, T. P., Robinson, W. H. 2012; 14 (1)

    Abstract

    Osteoarthritis (OA) is a degenerative disease characterized by cartilage breakdown in the synovial joints. The presence of low-grade inflammation in OA joints is receiving increasing attention, with synovitis shown to be present even in the early stages of the disease. How the synovial inflammation arises is unclear, but proteins in the synovial fluid of affected joints could conceivably contribute. We therefore surveyed the proteins present in OA synovial fluid and assessed their immunostimulatory properties.We used mass spectrometry to survey the proteins present in the synovial fluid of patients with knee OA. We used a multiplex bead-based immunoassay to measure levels of inflammatory cytokines in serum and synovial fluid from patients with knee OA and from patients with rheumatoid arthritis (RA), as well as in sera from healthy individuals. Significant differences in cytokine levels between groups were determined by significance analysis of microarrays, and relations were determined by unsupervised hierarchic clustering. To assess the immunostimulatory properties of a subset of the identified proteins, we tested the proteins' ability to induce the production of inflammatory cytokines by macrophages. For proteins found to be stimulatory, the macrophage stimulation assays were repeated by using Toll-like receptor 4 (TLR4)-deficient macrophages.We identified 108 proteins in OA synovial fluid, including plasma proteins, serine protease inhibitors, proteins indicative of cartilage turnover, and proteins involved in inflammation and immunity. Multiplex cytokine analysis revealed that levels of several inflammatory cytokines were significantly higher in OA sera than in normal sera, and levels of inflammatory cytokines in synovial fluid and serum were, as expected, higher in RA samples than in OA samples. As much as 36% of the proteins identified in OA synovial fluid were plasma proteins. Testing a subset of these plasma proteins in macrophage stimulation assays, we found that Gc-globulin, ?1-microglobulin, and ?2-macroglobulin can signal via TLR4 to induce macrophage production of inflammatory cytokines implicated in OA.Our findings suggest that plasma proteins present in OA synovial fluid, whether through exudation from plasma or production by synovial tissues, could contribute to low-grade inflammation in OA by functioning as so-called damage-associated molecular patterns in the synovial joint.

    View details for DOI 10.1186/ar3555

    View details for Web of Science ID 000304698800021

    View details for PubMedID 22225630

  • Amplitude and phasing of trunk motion is critical for the efficacy of gait training aimed at reducing ambulatory loads at the knee. Journal of biomechanical engineering Mündermann, A., Mündermann, L., Andriacchi, T. P. 2012; 134 (1): 011010-?

    Abstract

    The purpose of this study was to determine the contribution of changes in amplitude and phasing of medio-lateral trunk sway to a change in the knee adduction moment when walking with increased medio-lateral trunk sway. Kinematic and kinetic data of walking trials with normal and with increased trunk sway were collected for 19 healthy volunteers using a standard motion analysis system. The relationship between the change in first peak knee adduction moment (?KAM) and change in trunk sway amplitude (?SA; difference between maximum contralateral trunk lean and maximum ipsilateral trunk lean) and phasing (SP; time of heel-strike relative to time of maximum contralateral and time of maximum ipsilateral trunk lean) was determined using nonlinear regression analysis. On average, subjects increased their SA by 9.7?±?3.6 deg (P?

    View details for DOI 10.1115/1.4005540

    View details for PubMedID 22482665

  • Kinematics Differences Between the Flat, Kick, and Slice Serves Measured Using a Markerless Motion Capture Method ANNALS OF BIOMEDICAL ENGINEERING Sheets, A. L., Abrams, G. D., Corazza, S., Safran, M. R., Andriacchi, T. P. 2011; 39 (12): 3011-3020

    Abstract

    Tennis injuries have been associated with serving mechanics, but quantitative kinematic measurements in realistic environments are limited by current motion capture technologies. This study tested for kinematic differences at the lower back, shoulder, elbow, wrist, and racquet between the flat, kick, and slice serves using a markerless motion capture (MMC) system. Seven male NCAA Division 1 players were tested on an outdoor court in daylight conditions. Peak racquet and joint center speeds occurred sequentially and increased from proximal (back) to distal (racquet). Racquet speeds at ball impact were not significantly different between serve types. However, there were significant differences in the direction of the racquet velocity vector between serves: the kick serve had the largest lateral and smallest forward racquet velocity components, while the flat serve had the smallest vertical component (p < 0.01). The slice serve had lateral velocity, like the kick, and large forward velocity, like the flat. Additionally, the racquet in the kick serve was positioned 8.7 cm more posterior and 21.1 cm more medial than the shoulder compared with the flat, which could suggest an increased risk of shoulder and back injury associated with the kick serve. This study demonstrated the potential for MMC for testing sports performance under natural conditions.

    View details for DOI 10.1007/s10439-011-0418-y

    View details for Web of Science ID 000296507000014

    View details for PubMedID 21984513

  • Maintaining femoral bone density in adults: how many steps per day are enough? OSTEOPOROSIS INTERNATIONAL Boyer, K. A., Kiratli, B. J., Andriacchi, T. P., Beaupre, G. S. 2011; 22 (12): 2981-2988

    Abstract

    The amount and intensity of walking to maintain a healthy skeleton is unknown. This study examined the relationship between habitual walking activity and femoral bone mineral density (BMD) in healthy individuals using a quantitative theory for bone maintenance. Our results suggest a gender, weight, and speed sensitivity of walking interventions.Walking has been extensively promoted for the prevention of osteoporosis. The amount and intensity of walking to maintain a healthy skeleton is unknown and evidence to support a specific target of steps per day is lacking. The goal of our study was to examine the relationship between habitual walking activity and femoral bone mineral density (BMD) in healthy individuals using a quantitative theory for bone maintenance.Habitual walking activity and total femur BMD were measured in 105 individuals (49-64 years). An index of cumulative loading (bone density index, BDI) was examined as a predictor of BMD. The BDI-BMD relationship was used to predict the steps per day to maintain healthy BMD values for a range of body weights (BW) and walking speeds.For females but not for males, BDI was correlated with BMD (r (2) = 0.19, p < 0.001). The total required steps per day to maintain a T-score of -1.0 for a female with the average BW of the study cohort, walking at 1.00 m/s is 4,892 steps/day. Substantially more steps (18,568 steps/day) are required for a female with a BW 20% lighter than the average for our female cohort. For these lighter females, only at a walking speed greater than 1.32 m/s was 10,000 steps/day sufficient to maintain a T-score of -1.0.Our results suggest a gender, weight, and speed sensitivity of walking interventions for osteoporosis. In persons of low BW, the necessary steps per day to maintain BMD can be substantially greater than the often-quoted 10,000 steps.

    View details for DOI 10.1007/s00198-011-1538-9

    View details for Web of Science ID 000297151200006

    View details for PubMedID 21318440

  • Valgus Plus Internal Rotation Moments Increase Anterior Cruciate Ligament Strain More Than Either Alone MEDICINE AND SCIENCE IN SPORTS AND EXERCISE Shin, C. S., Chaudhari, A. M., Andriacchi, T. P. 2011; 43 (8): 1484-1491

    Abstract

    To test the influence of combined knee valgus and internal tibial rotation moment on anterior cruciate ligament (ACL) strain during single-leg landing. We tested the following hypotheses: the combination of the valgus and internal rotation moments observed during single-leg landing produces a higher ACL strain than either moment applied individually, the combined rotational moments at the physiological levels observed could theoretically increase strain in the ACL high enough to rupture the ACL, and the location of the peak contact force was at the posterior-lateral side for combined loading.The study was conducted by applying in vivo human loading data to a validated simulation model of the three-dimensional dynamic knee joint to predict ACL strains.The peak ACL strain increased nonlinearly when either applied valgus moment or internal rotation moment was increased in the model. When the two rotational moments were applied individually, neither caused ACL strain >0.077. However, when applied in combination, the two rotational moments had a much larger effect, and the predicted peak ACL strain increased up to 0.105. During landing, the peak contact force occurred at the posterior-lateral side of the tibial cartilage in the model when the combined maximum valgus moment and tibial internal rotation moments were applied.Combined knee valgus and internal rotation moments increases ACL strain more than either alone. The combination of a valgus and internal rotational moment at magnitudes that occurs in vivo during landing can cause ACL strains that may be high enough to cause ACL rupture. This predicted high ACL strain and the contact force location suggest that combined valgus and internal tibial rotational moments during single-leg landing are relevant to ACL injuries.

    View details for DOI 10.1249/MSS.0b013e31820f8395

    View details for Web of Science ID 000292773000013

    View details for PubMedID 21266934

  • A Wearable System to Assess Risk for Anterior Cruciate Ligament Injury During Jump Landing: Measurements of Temporal Events, Jump Height, and Sagittal Plane Kinematics JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Dowling, A. V., Favre, J., Andriacchi, T. P. 2011; 133 (7)

    Abstract

    The incidence of anterior cruciate ligament (ACL) injury remains high, and there is a need for simple, cost effective methods to identify athletes at a higher risk for ACL injury. Wearable measurement systems offer potential methods to assess the risk of ACL injury during jumping tasks. The objective of this study was to assess the capacity of a wearable inertial-based system to evaluate ACL injury risk during jumping tasks. The system accuracy for measuring temporal events (initial contact, toe-off), jump height, and sagittal plane angles (knee, trunk) was assessed by comparing results obtained with the wearable system to simultaneous measurements obtained with a marker-based optoelectronic reference system. Thirty-eight healthy participants (20 male and 18 female) performed drop jumps with bilateral and unilateral support landing. The mean differences between the temporal events obtained with both systems were below 5 ms, and the precisions were below 24 ms. The mean jump heights measured with both systems differed by less than 1 mm, and the associations (Pearson correlation coefficients) were above 0.9. For the discrete angle parameters, there was an average association of 0.91 and precision of 3.5° for the knee flexion angle and an association of 0.77 and precision of 5.5° for the trunk lean. The results based on the receiver-operating characteristic (ROC) also demonstrated that the proposed wearable system could identify movements at higher risk for ACL injury. The area under the ROC plots was between 0.89 and 0.99 for the knee flexion angle and between 0.83 and 0.95 for the trunk lean. The wearable system demonstrated good concurrent validity with marker-based measurements and good discriminative performance in terms of the known risk factors for ACL injury. This study suggests that a wearable system could be a simple cost-effective tool for conducting risk screening or for providing focused feedback.

    View details for DOI 10.1115/1.4004413

    View details for Web of Science ID 000293524800008

    View details for PubMedID 21823747

  • Preoperative and Postoperative Sagittal Plane Hip Kinematics in Patients With Femoroacetabular Impingement During Level Walking AMERICAN JOURNAL OF SPORTS MEDICINE Rylander, J. H., Shu, B., Andriacchi, T. P., Safran, M. R. 2011; 39: 36S-42S

    Abstract

    Femoroacetabular impingement (FAI) has been linked to osteoarthritis. Treatment options range from nonoperative to operative, and current outcome measures are generally subjective or not conducted under actual activities of daily living. Thus, there is a need for the use of motion capture techniques to quantitatively assess the outcome of surgical intervention for those treated for FAI.The gait of FAI patients 1 year after operative treatment (arthroscopic hip reshaping) will be significantly closer to the normal range and pattern of hip flexion motion, relative to pretreatment.Case series; Level of evidence, 4.Eleven patients between 18 and 44 years of age with diagnosed FAI were enrolled in this study. Kinematics and kinetics for this group of patients were collected using motion capture techniques before arthroscopic bone-reshaping surgery and again 1 year after surgery. Pain and perceived activity level (Tegner scale) were also collected. All collected data were compared using a paired t test.Overall hip sagittal plane range of motion increased on the affected side from 27.6° ± 5.0° to 30.7° ± 4.3° (P = .02). The presence of abnormal reversals (second-order change in the slope in the hip flexion/extension curve) that was present in 5 patients preoperatively disappeared or was reduced in prevalence and magnitude in 4 of the patients postoperatively. Additionally, pain decreased and activity level increased postoperatively.The results supported the hypothesis that surgical intervention for FAI restores more normal patterns of gait and provides objective support that the surgical procedure is useful. The results help establish motion capture as a potential method for quantitatively assessing the outcome in FAI surgical interventions. The presence of abnormal reversals in hip flexion has been reported in end-stage hip osteoarthritis, and the presence of these reversals in FAI patients reinforces the idea of FAI being a precursor to hip osteoarthritis.

    View details for DOI 10.1177/0363546511413993

    View details for Web of Science ID 000292167400006

    View details for PubMedID 21709030

  • Knee joint kinematics during walking influences the spatial cartilage thickness distribution in the knee JOURNAL OF BIOMECHANICS Koo, S., Rylander, J. H., Andriacchi, T. P. 2011; 44 (7): 1405-1409

    Abstract

    The regional adaptation of knee cartilage morphology to the kinematics of walking has been suggested as an important factor in the evaluation of the consequences of alteration in normal gait leading to osteoarthritis. The purpose of this study was to investigate the association of spatial cartilage thickness distributions of the femur and tibia in the knee to the knee kinematics during walking. Gait data and knee MR images were obtained from 17 healthy volunteers (age 33.2 ± 9.8 years). Cartilage thickness maps were created for the femoral and tibial cartilage. Locations of thickest cartilage in the medial and lateral compartments in the femur and tibia were identified using a numerical method. The flexion-extension (FE) angle associated with the cartilage contact regions on the femur, and the anterior-posterior (AP) translation and internal-external (IE) rotation associated with the cartilage contact regions on the tibia at the heel strike of walking were tested for correlation with the locations of thickest cartilage. The locations of the thickest cartilage had relatively large variation (SD, 8.9°) and was significantly associated with the FE angle at heel strike only in the medial femoral condyle (R(2)=0.41, p<0.01). The natural knee kinematics and contact surface shapes seem to affect the functional adaptation of knee articular cartilage morphology. The sensitivity of cartilage morphology to kinematics at the knee during walking suggests that regional cartilage thickness variations are influenced by both loading and the number of loading cycles. Thus walking is an important consideration in the analysis of the morphological variations of articular cartilage, since it is the dominant cyclic activity of daily living. The sensitivity of cartilage morphology to gait kinematics is also important in understanding the etiology and pathomechanics of osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2010.11.020

    View details for Web of Science ID 000291075800027

    View details for PubMedID 21371712

  • An analysis of the mechanisms for reducing the knee adduction moment during walking using a variable stiffness shoe in subjects with knee osteoarthritis JOURNAL OF BIOMECHANICS Jenkyn, T. R., Erhart, J. C., Andriacchi, T. P. 2011; 44 (7): 1271-1276

    Abstract

    Variable stiffness shoes that have a stiffer lateral than medial sole may reduce the external knee adduction moment (EKAM) and pain during walking in patients with medial compartment knee osteoarthritis (OA). However, the mechanism by which EKAM may be reduced in the OA knee with this intervention remains unclear. Three hypotheses were tested in this study: (1) The reduction in EKAM during walking with the variable stiffness shoe is associated with a reduction in GRF magnitude and/or (2) frontal plane lever arm. (3) A reduction in frontal plane lever arm occurs either by moving the center of pressure laterally under the shoe and/or by dynamically reducing the medial component of GRF. Thirty-two subjects (20 male, 12 female; age: 58.7 ± 9.3 years; height: 1.62 ± 0.08 m; mass: 81.3 ± 14.6 kg) with medial compartment knee osteoarthritis were studied walking in a gait laboratory. The frontal plane lever arm was significantly reduced (1.62%, 0.07%ht, p=0.02) on the affected side while the magnitude of the GRF was not significantly changed. The reduction in the lever arm was weakly correlated with a medial shift in the COP. However, the combined medial shift in the COP and reduction in the medial GRF explained 50% of the change of the frontal plane lever arm. These results suggest that the medial shift in the COP at the foot produced by the intervention shoe stimulates an adaptive dynamic response during gait that reduces the frontal plane lever arm.

    View details for DOI 10.1016/j.jbiomech.2011.02.013

    View details for Web of Science ID 000291075800007

    View details for PubMedID 21396645

  • The Effect of Kinematic and Kinetic Changes on Meniscal Strains During Gait JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Netravali, N. A., Koo, S., Giori, N. J., Andriacchi, T. P. 2011; 133 (1)

    Abstract

    The menisci play an important role in load distribution, load bearing, joint stability, lubrication, and proprioception. Partial meniscectomy has been shown to result in changes in the kinematics and kinetics at the knee during gait that can lead to progressive meniscal degeneration. This study examined changes in the strains within the menisci associated with kinematic and kinetic changes during the gait cycle. The gait changes considered were a 5 deg shift toward external rotation of the tibia with respect to the femur and an increased medial-lateral load ratio representing an increased adduction moment. A finite element model of the knee was developed and tested using a cadaveric specimen. The cadaver was placed in positions representing heel-strike and midstance of the normal gait, and magnetic resonance images were taken. Comparisons of the model predictions to boundaries digitized from images acquired in the loaded states were within the errors produced by a 1 pixel shift of either meniscus. The finite element model predicted that an increased adduction moment caused increased strains of both the anterior and posterior horns of the medial meniscus. The lateral meniscus exhibited much lower strains and had minimal changes under the various loading conditions. The external tibial rotational change resulted in a 20% decrease in the strains in the posterior medial horn and increased strains in the anterior medial horn. The results of this study suggest that the shift toward external tibial rotation seen clinically after partial medial meniscectomy is not likely to cause subsequent degenerative medial meniscal damage, but the consequence of this kinematic shift on the pathogenesis of osteoarthritis following meniscectomy requires further consideration.

    View details for DOI 10.1115/1.4003008

    View details for Web of Science ID 000285767600006

    View details for PubMedID 21186896

  • Review of tennis serve motion analysis and the biomechanics of three serve types with implications for injury SPORTS BIOMECHANICS Abrams, G. D., Sheets, A. L., Andriacchi, T. P., Safran, M. R. 2011; 10 (4): 378-390

    Abstract

    The tennis serve has the potential for musculoskeletal injury as it is an overhead motion and is performed repetitively during play. Early studies evaluating the biomechanics and injury potential of the tennis serve utilized skin-based marker technologies; however, markerless motion measurement systems have recently become available and have obviated some of the problems associated with the marker-based technology. The late cocking and early acceleration phases of the kinetic chain of the service motion produce the highest internal forces and pose the greatest risk of injury during the service motion. Previous biomechanical data on the tennis serve have primarily focused on the flat serve, with some data on the kick serve, and very little published data elucidating the biomechanics of the slice serve. This review discusses the injury potential of the tennis serve with respect to the four phases of the service motion, the history, and early findings of service motion evaluation, as well as biomechanical data detailing the differences between the three types of serves and how this may relate to injury prevention, rehabilitation, and return to play.

    View details for DOI 10.1080/14763141.2011.629302

    View details for Web of Science ID 000299832400010

    View details for PubMedID 22303788

  • Changes in In Vivo Knee Loading with a Variable-Stiffness Intervention Shoe Correlate with Changes in the Knee Adduction Moment JOURNAL OF ORTHOPAEDIC RESEARCH Erhart, J. C., Dyrby, C. O., D'Lima, D. D., Colwell, C. W., Andriacchi, T. P. 2010; 28 (12): 1548-1553

    Abstract

    External knee adduction moment can be reduced using footwear interventions, but the exact changes in in vivo medial joint loading remain unknown. An instrumented knee replacement was used to assess changes in in vivo medial joint loading in a single patient walking with a variable-stiffness intervention shoe. We hypothesized that during walking with a load modifying variable-stiffness shoe intervention: (1) the first peak knee adduction moment will be reduced compared to a subject's personal shoes; (2) the first peak in vivo medial contact force will be reduced compared to personal shoes; and (3) the reduction in knee adduction moment will be correlated with the reduction in medial contact force. The instrumentation included a motion capture system, force plate, and the instrumented knee prosthesis. The intervention shoe reduced the first peak knee adduction moment (13.3%, p = 0.011) and medial compartment joint contact force (12.3%; p = 0.008) compared to the personal shoe. The change in first peak knee adduction moment was significantly correlated with the change in first peak medial contact force (R(2)?= 0.67, p = 0.007). Thus, for a single subject with a total knee prosthesis the variable-stiffness shoe reduces loading on the affected compartment of the joint. The reductions in the external knee adduction moment are indicative of reductions in in vivo medial compressive force with this intervention.

    View details for DOI 10.1002/jor.21183

    View details for Web of Science ID 000284026000002

    View details for PubMedID 20973058

  • Partial medial meniscectomy and rotational differences at the knee during walking JOURNAL OF BIOMECHANICS Netravali, N. A., Giori, N. J., Andriacchi, T. P. 2010; 43 (15): 2948-2953

    Abstract

    Loss of meniscal function due to injury or partial meniscectomy is common and represents a significant risk factor for premature osteoarthritis. The menisci can influence the transverse plane movements (anterior-posterior (AP) translation and internal-external (IE) rotation) of the knee during walking. While walking is the most frequent activity of daily living, the kinematic differences at the knee during walking associated with the meniscal injury are not well understood. This study examined the influence of partial medial meniscectomy (PMM) on the kinematics and kinetics of the knee during the stance phase of gait by testing the differences in anterior-posterior translation, internal-external rotation, knee flexion range of movement, peak flexion/extension moments, and adduction moments between the PMM and healthy contralateral limbs. Ten patients (45±9 years old, height 1.75±0.06m, weight 76.7±13.5kg) who had undergone partial medial meniscectomy (33±100 months post-op) in one limb with a healthy contralateral limb were tested during normal walking. The contralateral limb was compared to a matched control group and no differences were found. The primary kinematic difference was a significantly greater external rotation (3.2°) of the tibia that existed through stance phase, with 8 of 10 subjects demonstrating the same pattern. The PMM subjects also exhibited significantly lower peak flexion and extension moments in their PMM limbs. The altered rotational position found likely results in changes of tibio-femoral contact during walking and could cause the type of degenerative changes found in the articular cartilage following meniscal injury.

    View details for DOI 10.1016/j.jbiomech.2010.07.013

    View details for Web of Science ID 000285122900013

    View details for PubMedID 20719317

  • Changes in knee adduction moment, pain, and functionality with a variable-stiffness walking shoe after 6 months. Journal of orthopaedic research Erhart, J. C., Mündermann, A., Elspas, B., Giori, N. J., Andriacchi, T. P. 2010; 28 (7): 873-879

    Abstract

    This study tested the effects of variable-stiffness shoes on knee adduction moment, pain, and function in subjects with symptoms of medial compartment knee osteoarthritis over 6 months. Patients were randomly and blindly assigned to a variable-stiffness intervention or constant-stiffness control shoe. The Western Ontario and McMaster Universities (WOMAC) score served as the primary outcome measure. Joint loading, the secondary outcome measure, was assessed using the external knee adduction moment. Peak external knee adduction moment, total WOMAC, and WOMAC pain scores were assessed at baseline and after 6 months. The total WOMAC and WOMAC pain scores for the intervention group were reduced from baseline to 6 months (p = 0.017 and p = 0.002, respectively), with no significant reductions for the control group. There was no difference between groups in magnitude of the reduction in total WOMAC (p = 0.50) or WOMAC pain scores (p = 0.31). The proportion of patients achieving a clinically important improvement in pain was greater in the intervention group than in the control group (p = 0.012). The variable-stiffness shoes reduced the peak knee adduction moment (-6.6% vs. control, p < 0.001) in the 34 intervention subjects at 6 months. The adduction moment reduction significantly improved (p = 0.03) from the baseline reduction. The constant-stiffness control shoe increased the peak knee adduction moment (+6.3% vs. personal, p = 0.004) in the 26 control subjects at 6 months. The results of this study showed that wearing the variable-stiffness shoe lowered the adduction moment, reduced pain, and improved functionality after 6 months of wear. The lower adduction moment associated with wearing this shoe may slow the rate of progression of osteoarthritis after long-term use.

    View details for DOI 10.1002/jor.21077

    View details for PubMedID 20058261

  • Gait Modification via Verbal Instruction and an Active Feedback System to Reduce Peak Knee Adduction Moment JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Dowling, A. V., Fisher, D. S., Andriacchi, T. P. 2010; 132 (7)

    Abstract

    The purpose of this study was to introduce a simple gait training method using real-time gait modification to reduce the peak knee adduction moment during walking by producing a subtle weight bearing shift to the medial side of the foot. The hypothesis of this study was that this weight shift could be achieved via either verbal instruction or an active feedback system, and that the weight shift would result in a reduction in the first peak knee adduction moment compared with the control tests. Nine individuals were tested during walking using two intervention methods: verbal instruction and an active feedback system placed on the right shoe. The first peak of the knee adduction moment for each condition was assessed using a motion capture system and force plate. The active feedback system significantly reduced (14.2%) the peak knee adduction moment relative to the control. This study demonstrated that a subtle weight bearing shift to the medial side of the foot produced with an active feedback system during walking reduced the first peak of the knee adduction moment and suggests the potential application of this method to slow the rate of progression of medial compartment knee osteoarthritis.

    View details for DOI 10.1115/1.4001584

    View details for Web of Science ID 000279631400007

    View details for PubMedID 20590285

  • Gait Changes in Patients With Knee Osteoarthritis Are Replicated by Experimental Knee Pain ARTHRITIS CARE & RESEARCH Henriksen, M., Graven-Nielsen, T., Aaboe, J., Andriacchi, T. P., Bliddal, H. 2010; 62 (4): 501-509

    Abstract

    Medial knee osteoarthritis (OA) is characterized by pain and associated with abnormal knee moments during walking. The relationship between knee OA pain and gait changes remains to be clarified, and a better understanding of this link could advance the treatment and prevention of disease progression. This study investigated changes in knee moments during walking following experimental knee pain in healthy volunteers, and whether these changes replicated the joint moments observed in medial knee OA patients.In a crossover study, 34 healthy subjects were tested on 3 different days; gait analyses were conducted before, during, and after pain induced by hypertonic saline injections (0.75 ml) into the infrapatellar fat pad. Isotonic saline and sham injections were used as control conditions. Peak moments in frontal and sagittal planes were analyzed. The results were compared with data from 161 medial knee OA patients. The patients were divided into less severe OA and severe OA categories, which was based on radiographic disease severity of the medial compartment.Experimental knee pain led to reduced peak moments in the frontal and sagittal planes in the healthy subjects, which were similar to the patterns observed in less severe OA patients while walking at the same speed.In healthy subjects, pain was associated with reductions in knee joint moments during walking in a manner similar to less severe knee OA patients. The experimental model may be used to study mechanically-driven knee OA progression and preventive measures against abnormal joint loading in knee OA.

    View details for DOI 10.1002/acr.20033

    View details for Web of Science ID 000280979400011

    View details for PubMedID 20391505

  • Automatic Generation of a Subject-Specific Model for Accurate Markerless Motion Capture and Biomechanical Applications IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Corazza, S., Gambaretto, E., Mundermann, L., Andriacchi, T. P. 2010; 57 (4): 806-812

    Abstract

    A novel approach for the automatic generation of a subject-specific model consisting of morphological and joint location information is described. The aim is to address the need for efficient and accurate model generation for markerless motion capture (MMC) and biomechanical studies. The algorithm applied and expanded on previous work on human shapes space by embedding location information for ten joint centers in a subject-specific free-form surface. The optimal locations of joint centers in the 3-D mesh were learned through linear regression over a set of nine subjects whose joint centers were known. The model was shown to be sufficiently accurate for both kinematic (joint centers) and morphological (shape of the body) information to allow accurate tracking with MMC systems. The automatic model generation algorithm was applied to 3-D meshes of different quality and resolution such as laser scans and visual hulls. The complete method was tested using nine subjects of different gender, body mass index (BMI), age, and ethnicity. Experimental training error and cross-validation errors were 19 and 25 mm, respectively, on average over the joints of the ten subjects analyzed in the study.

    View details for DOI 10.1109/TBME.2008.2002103

    View details for Web of Science ID 000275998200005

    View details for PubMedID 19272951

  • Markerless Motion Capture through Visual Hull, Articulated ICP and Subject Specific Model Generation INTERNATIONAL JOURNAL OF COMPUTER VISION Corazza, S., Muendermann, L., Gambaretto, E., Ferrigno, G., Andriacchi, T. P. 2010; 87 (1-2): 156-169
  • Shoe-Surface Friction Influences Movement Strategies During a Sidestep Cutting Task Implications for Anterior Cruciate Ligament Injury Risk AMERICAN JOURNAL OF SPORTS MEDICINE Dowling, A. V., Corazza, S., Chaudhari, A. M., Andriacchi, T. P. 2010; 38 (3): 478-485

    Abstract

    Increasing the coefficient of friction of the shoe-surface interaction has been shown to lead to increased incidence of anterior cruciate ligament (ACL) injuries, but the causes for this increase are unknown. Previous studies indicate that specific biomechanical measures during landing are associated with an increased risk for ACL injury.At foot contact during a sidestep cutting task, subjects use different movement strategies for shoe-surface conditions with a high coefficient of friction (COF) relative to a low friction condition. Specifically, the study tested for significant differences in knee kinematics, external knee moments, and the position of the center of mass for different COFs.Controlled laboratory study.Twenty-two healthy subjects (11 male) were evaluated performing a 30 degrees sidestep cutting task on a low friction surface (0.38) and a high friction surface (0.87) at a constant speed. An 8-camera markerless motion capture system combined with 2 force plates was used to measure full-body kinematics, kinetics, and center of mass.At foot contact, subjects had a lower knee flexion angle (P = .01), lower external knee flexion moment (P < .001), higher external knee valgus moment (P < .001), and greater medial distance of the center of mass from the support limb (P < .001) on the high friction surface relative to the low friction surface.The high COF shoe-surface condition was associated with biomechanical conditions that can increase the risk of ACL injury. The higher incidence of ACL injury observed on high friction surfaces could be a result of these biomechanical changes. The differences in the biomechanical variables were the result of an anticipated stimulus due to different surface friction, with other conditions remaining constant.The risk analysis of ACL injury should consider the biomechanical movement changes that occur for a shoe-surface condition with high friction.

    View details for DOI 10.1177/0363546509348374

    View details for Web of Science ID 000274803800006

    View details for PubMedID 20194954

  • Muscle and Joint Function in Human Locomotion ANNUAL REVIEW OF BIOMEDICAL ENGINEERING, VOL 12 Pandy, M. G., Andriacchi, T. P. 2010; 12: 401-433

    Abstract

    This review describes how computational modeling can be combined with noninvasive gait measurements to describe and explain muscle and joint function in human locomotion. Five muscles--the gluteus maximus, gluteus medius, vasti, soleus, and gastrocnemius--contribute most significantly to the accelerations of the center of mass in the vertical, fore-aft, and medio-lateral directions when humans walk and run at their preferred speeds. Humans choose to switch from a walk to a run at speeds near 2 m s(-1) to enhance the biomechanical performance of the ankle plantarflexors and to improve coordination of the knee and ankle muscles during stance. Muscles that do not span a joint can contribute to the contact force transmitted by that joint and therefore affect its stability. In walking, for example, uniarticular muscles that cross the hip and ankle act to create the adduction moment at the knee, thereby contributing to the contact force present in the medial compartment.

    View details for DOI 10.1146/annurev-bioeng-070909-105259

    View details for Web of Science ID 000281447400016

    View details for PubMedID 20617942

  • REDUCTION IN THE KNEE ADDUCTION MOMENT DURING WALKING USING LATERALLY-WEDGED SHOES WITH AND WITHOUT ANKLE SUPPORT PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, 2010 Erhart, J., Andriacchi, T. 2010: 307-308
  • RELATIONSHIP OF KNEE ARTICULAR CARTILAGE THICKNESS TO BODY MASS INDEX AND GAIT MECHANICS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, 2010 Blazek, K., Erhart, J., Asay, J., Andriacchi, T. 2010: 411-412
  • An Automated Image-Based Method of 3D Subject-Specific Body Segment Parameter Estimation for Kinetic Analyses of Rapid Movements JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Sheets, A. L., Corazza, S., Andriacchi, T. P. 2010; 132 (1)

    Abstract

    Accurate subject-specific body segment parameters (BSPs) are necessary to perform kinetic analyses of human movements with large accelerations, or no external contact forces or moments. A new automated topographical image-based method of estimating segment mass, center of mass (CM) position, and moments of inertia is presented. Body geometry and volume were measured using a laser scanner, then an automated pose and shape registration algorithm segmented the scanned body surface, and identified joint center (JC) positions. Assuming the constant segment densities of Dempster, thigh and shank masses, CM locations, and moments of inertia were estimated for four male subjects with body mass indexes (BMIs) of 19.7-38.2. The subject-specific BSP were compared with those determined using Dempster and Clauser regression equations. The influence of BSP and BMI differences on knee and hip net forces and moments during a running swing phase were quantified for the subjects with the smallest and largest BMIs. Subject-specific BSP for 15 body segments were quickly calculated using the image-based method, and total subject masses were overestimated by 1.7-2.9%.When compared with the Dempster and Clauser methods, image-based and regression estimated thigh BSP varied more than the shank parameters. Thigh masses and hip JC to thigh CM distances were consistently larger, and each transverse moment of inertia was smaller using the image-based method. Because the shank had larger linear and angular accelerations than the thigh during the running swing phase, shank BSP differences had a larger effect on calculated intersegmental forces and moments at the knee joint than thigh BSP differences did at the hip. It was the net knee kinetic differences caused by the shank BSP differences that were the largest contributors to the hip variations. Finally, BSP differences produced larger kinetic differences for the subject with larger segment masses, suggesting that parameter accuracy is more important for studies focused on overweight populations. The new image-based BSP estimation method described in this paper addressed the limitations of currently used geometric and regression methods by using exact limb geometry to determine subject-specific parameters. BSP differences have the largest effect on kinetic analyses of motions with large limb accelerations, for joints farther along the kinematic chain from the known forces and moments, and for subjects with larger limb masses or BMIs.

    View details for DOI 10.1115/1.4000155

    View details for Web of Science ID 000274106900004

    View details for PubMedID 20524742

  • Changes in running kinematics and kinetics in response to a rockered shoe intervention CLINICAL BIOMECHANICS Boyer, K. A., Andriacchi, T. P. 2009; 24 (10): 872-876

    Abstract

    A suggested link between ambulatory mechanics and injury development has resulted in significant interest the development of footwear to change locomotion patterns. The purpose of this study was to test the hypothesis that there will be significant changes in the kinematics and kinetics at the ankle and minimal changes at the knee and hip in the mechanics of running in a shoe with a sagittal plane curvature relative to a flat soled shoe.During running 3-D lower extremity kinematics and kinetics for 19 healthy volunteers were quantified using an optoelectronics system and a force plate. Data were collected for a flat sole conventional shoe (New Balance 658 (Control)) and a shoe with a rounded sole in the sagittal plane (Masai Barefoot Technologies (MBT)). Data were compared for the two shoe conditions using paired Student t-tests (alpha=0.05).The ankle dorsi-flexion angles at heel-strike and mid-stance were greater, while the ankle plantar and dorsi-flexion moments and peak ankle joint power were significantly lower with the MBT relative to the control (P<0.05). Decreases in the first medial GRF peak and the peak anterior GRF peak were also found for running in the MBT shoe.Despite a major difference in sole geometry, accommodations to the rockered sole were found only at the ankle. These results suggest changes in ankle kinematics and kinetics may be used to minimize the effect of changes in sole rocker on limb dynamics. Thus, changes in shoe rocker may offer potential therapeutic opportunities for running related conditions at the ankle without substantial risk to the knee or hip.

    View details for DOI 10.1016/j.clinbiomech.2009.08.003

    View details for Web of Science ID 000271784700014

    View details for PubMedID 19744753

  • Accuracy of 3D Cartilage Models Generated From MR Images Is Dependent on Cartilage Thickness: Laser Scanner Based Validation of In Vivo Cartilage JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Koo, S., Giori, N. J., Gold, G. E., Dyrby, C. O., Andriacchi, T. P. 2009; 131 (12)

    Abstract

    Cartilage morphology change is an important biomarker for the progression of osteoarthritis. The purpose of this study was to assess the accuracy of in vivo cartilage thickness measurements from MR image-based 3D cartilage models using a laser scanning method and to test if the accuracy changes with cartilage thickness. Three-dimensional tibial cartilage models were created from MR images (in-plane resolution of 0.55 mm and thickness of 1.5 mm) of osteoarthritic knees of ten patients prior to total knee replacement surgery using a semi-automated B-spline segmentation algorithm. Following surgery, the resected tibial plateaus were laser scanned and made into 3D models. The MR image and laser-scan based models were registered to each other using a shape matching technique. The thicknesses were compared point wise for the overall surface. The linear mixed-effects model was used for statistical test. On average, taking account of individual variations, the thickness measurements in MRI were overestimated in thinner (<2.5 mm) regions. The cartilage thicker than 2.5 mm was accurately predicted in MRI, though the thick cartilage in the central regions was underestimated. The accuracy of thickness measurements in the MRI-derived cartilage models systemically varied according to native cartilage thickness.

    View details for DOI 10.1115/1.4000087

    View details for Web of Science ID 000273614400004

    View details for PubMedID 20524727

  • Vibration training intervention to maintain cartilage thickness and serum concentrations of cartilage oligometric matrix protein (COMP) during immobilization OSTEOARTHRITIS AND CARTILAGE Liphardt, A., Muendermann, A., Koo, S., Baecker, N., Andriacchi, T. P., Zange, J., Mester, J., Heer, M. 2009; 17 (12): 1598-1603

    Abstract

    To test the hypotheses that 1) 14-days of immobilization of young healthy subjects using a 6 degrees -"head-down-tilt-bed-rest"-model (6 degrees -HDT) would reduce cartilage thickness in the knee and serum Cartilage oligometric matrix protein (COMP) concentration and 2) isolated whole body vibration training would counteract the bed rest effects.The study was performed and designed in compliance with the Declaration of Helsinki and is registered as trial DRKS00000140 in the German Clinical Trial Register (register.germanctr.de). Eight male healthy subjects (78.0+/-9.5kg; 179+/-0.96cm, 26+/-5 years) performed 14 days of 6 degrees -HDT. The study was designed as a cross-over-design with two study phases: a training and a control intervention. During the training intervention, subjects underwent 2x5-min whole body vibration training/day (Frequency: 20Hz; amplitude: 2-4mm). Magnetic resonance (MR) images (slice thickness: 2mm; in-plane resolution: 0.35x0.35mm; pixels: 448x512) were taken before and after the 6 degrees -HDT periods. Average cartilage thicknesses were calculated for the load bearing regions on the medial and lateral articulating surfaces in the femur and tibia.While the control intervention resulted in an overall loss in average cartilage thickness of -8% (pre: 3.08mm+/-0.6mm post: 2.82mm+/-0.6mm) in the weight-bearing regions of the tibia, average cartilage thickness increased by 21.9% (pre: 2.66mm+/-0.45mm post: 3.24mm+/-0.63mm) with the vibration intervention. No significant differences were found in the weight-bearing regions of the femur. During both interventions, reduced serum COMP concentrations were observed (control intervention: -13.6+/-8.4%; vibration intervention: -9.9+/-3.3%).The results of this study suggest that articular cartilage thickness is sensitive to unloading and that vibration training may be a potent countermeasure against these effects. The sensitivity of cartilage to physical training is of high relevance for training methods in space flight, elite and sport and rehabilitation after illness or injury.

    View details for DOI 10.1016/j.joca.2009.07.007

    View details for Web of Science ID 000272966700011

    View details for PubMedID 19747585

  • Change in Serum COMP Concentration Due to Ambulatory Load Is Not Related to Knee OA Status JOURNAL OF ORTHOPAEDIC RESEARCH Muendermann, A., King, K. B., Smith, L., Andriacchi, T. P. 2009; 27 (11): 1408-1413

    Abstract

    The aim of this study was to test the hypothesis that a change in serum cartilage oligomeric matrix protein (COMP) concentration is related to joint load during a 30-min walking exercise in patients with medial compartment knee osteoarthritis (OA) and in age-matched control subjects. Blood samples were drawn from 42 patients with medial compartment knee OA and from 41 healthy age-matched control subjects immediately before, immediately after, and 0.5, 1.5, 3.5, and 5.5 h after a 30-min walking exercise on a level outdoor walking track at self-selected normal speed. Serum COMP concentrations were determined using a commercial ELISA. Basic time-distance gait variables were recorded using an activity monitor. Joint loads were measured using gait analysis. Serum COMP concentrations increased immediately after the walking exercise (+6.3% and +5.6%; p < 0.001) and decreased over 5.5 h after the exercise (-11.1% and -14.6%; p < 0.040 and p = 0.001) in patients and control subjects, respectively. The magnitude of increase in COMP concentration did not differ between groups (p = 0.902) and did not correlate with any variables describing ambulatory loads at the joints of the lower extremity. These results, taken together with a previous study of a younger healthy population, suggest the possibility that the influence of ambulatory loads on cartilage turnover is dependent on age.

    View details for DOI 10.1002/jor.20908

    View details for Web of Science ID 000271310700002

    View details for PubMedID 19422040

  • Graft Orientation Influences the Knee Flexion Moment During Walking in Patients With Anterior Cruciate Ligament Reconstruction AMERICAN JOURNAL OF SPORTS MEDICINE Scanlan, S. F., Blazek, K., Chaudhari, A. M., Safran, M. R., Andriacchi, T. P. 2009; 37 (11): 2173-2178

    Abstract

    Anterior cruciate ligament graft orientation has been proposed as a potential mechanism for failure of single-bundle anterior cruciate ligament reconstruction and has been considered important in the restoration of normal ambulatory knee mechanics.To evaluate the possibility that patients adapt their mechanics of walking to the orientation of the anterior cruciate ligament graft. This was determined by testing the hypothesis that peak external knee flexion moment (net quadriceps moment) during walking in patients with anterior cruciate ligament reconstruction is correlated with coronal and sagittal anterior cruciate ligament graft orientations.Cross-sectional study; Level of evidence, 3.Gait analysis was performed to assess dynamic knee function during walking in 17 subjects with unilateral anterior cruciate ligament reconstructions. Magnetic resonance imaging was used to measure coronal and sagittal anterior cruciate ligament graft orientations.A negative correlation was observed between peak external knee flexion moment during walking and coronal angle of the anterior cruciate ligament graft (1.0 m/s walking speed, r = -0.87, P < .001; 1.3 m/s, r = -0.66, P = .004; 1.6 m/s, r = -0.24, P > .05); no correlation was found with the sagittal graft angle (1.0 m/s walking speed, r = 0.21, P > .05; 1.3 m/s, r = 0.20, P > .05; 1.6 m/s, r = 0.13, P > .05).The negative correlation between peak external knee flexion moment during walking and the coronal angle of the anterior cruciate ligament graft indicates that as the anterior cruciate ligament graft is placed in a more vertical coronal orientation, patients reduce their net quadriceps usage during walking.This finding supports the hypothesis that graft placement plays a critical role in the restoration of normal ambulatory mechanics after anterior cruciate ligament reconstruction and thus could provide a partial explanation for the increased incidence of premature osteoarthritis at long-term follow-up in patients with anterior cruciate ligament reconstruction.

    View details for DOI 10.1177/0363546509339574

    View details for Web of Science ID 000271216600012

    View details for PubMedID 19729363

  • Central and peripheral region tibial plateau chondrocytes respond differently to in vitro dynamic compression OSTEOARTHRITIS AND CARTILAGE Bevill, S. L., Briant, P. L., Levenston, M. E., Andriacchi, T. P. 2009; 17 (8): 980-987

    Abstract

    The objective of this study was to test the hypotheses that chondrocytes from distinct regions of the porcine tibial plateau: (1) display region-specific baseline gene expression, and (2) respond differently to in vitro mechanical loading.Articular cartilage explants were obtained from central (not covered by meniscus) and peripheral (covered by meniscus) regions of porcine tibial plateaus. For baseline gene expression analysis, samples were snap frozen. To determine the effect of mechanical loading, central and peripheral region explants were exposed to equivalent dynamic compression (0-100 kPa) and compared to site-matched free-swelling controls (FSCs). mRNA levels for type II collagen (CII), aggrecan (AGGR), matrix metalloproteinase 1 (MMP-1), MMP-3, MMP-13, A disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAM-TS4), ADAM-TS5, tissue inhibitor of metalloproteinases 1 (TIMP-1), TIMP-2, and tumor necrosis factor alpha (TNFalpha) were quantified using real time polymerase chain reaction (RT-PCR).At baseline, mRNA levels for the structural proteins CII and AGGR were approximately twofold greater in the central region compared with peripheral region explants. In vitro dynamic compression strongly affected expression levels for CII, AGGR, MMP-3, and TIMP-2 relative to FSCs. Response differed significantly by region, with greater upregulation of CII, AGGR, and MMP-3 in central region explants.Chondrocytes from different regions of the porcine tibial plateau express mRNA for structural proteins at different levels and respond to equivalent in vitro mechanical loading with distinctive changes in gene expression. These regional biological variations appear to be related to the local mechanical environment in the normal joint, and thus may indicate a sensitivity of the joint to conditions that alter joint loading such as anterior cruciate ligament (ACL) injury, meniscectomy, or joint instability.

    View details for DOI 10.1016/j.joca.2008.12.005

    View details for Web of Science ID 000268654700003

    View details for PubMedID 19157913

  • Influence of Patellar Ligament Insertion Angle on Quadriceps Usage during Walking in Anterior Cruciate Ligament Reconstructed Subjects JOURNAL OF ORTHOPAEDIC RESEARCH Shin, C. S., Chaudhari, A. A., Dyrby, C. O., Andriacchi, T. P. 2009; 27 (6): 730-735

    Abstract

    Reduced quadriceps contraction has been suggested as an adaptation to prevent anterior tibial translation in anterior cruciate ligament (ACL)-deficient knees. This theory has been supported by a recent study that peak knee flexion moment (thought to be created by a decrease of quadriceps contraction) during walking was negatively correlated with patellar ligament insertion angle (PLIA) in ACL-deficient knees, but not in contralateral, uninjured knees. In addition, the PLIA was significantly smaller in ACL-deficient knees than in contralateral, uninjured knees. However, it is unknown whether ACL reconstruction restores the PLIA or whether the relationship between the PLIA and knee flexion moments previously observed in ACL-deficient knees disappears. This study tested the following hypotheses: (1) The PLIA of ACL-reconstructed knees is significantly smaller than the PLIA of uninjured contralateral knees; (2) Peak knee flexion moment (balanced by net quadriceps moment) during walking is negatively correlated with the PLIA in ACL-reconstructed knees. The PLIA of 24 ACL-reconstructed and contralateral knees were measured using MRI, and peak knee flexion moments during walking were measured. Results showed that the PLIA of ACL-reconstructed (22.9 +/- 4.4 degrees) knees was not significantly smaller (p = 0.09, power = 0.99) than the PLIA of contralateral (24.1 +/- 4.8 degrees) knees. Peak knee flexion moment was not correlated with the PLIA following ACL reconstruction (R2 = 0.016, power = 0.99). However, the magnitude of the knee flexion moment remained significantly lower in ACL-reconstructed knees. In summary, this study has shown that the PLIA of ACL-reconstructed knees returned to normal and that patients no longer adapt their gait in response to the PLIA, though quadriceps function did not return to normal levels.

    View details for DOI 10.1002/jor.20806

    View details for Web of Science ID 000266123100005

    View details for PubMedID 19025774

  • Adaptive Patterns of Movement during Stair Climbing in Patients with Knee Osteoarthritis JOURNAL OF ORTHOPAEDIC RESEARCH Asay, J. L., Muendermann, A., Andriacchi, T. P. 2009; 27 (3): 325-329

    Abstract

    The purpose of this study was to determine if there is a distinctive characteristic in the pattern of movement (forward trunk lean to reduce demand on the quadriceps muscle) during stair climbing in patients with knee osteoarthritis (OA) that is associated with the severity of the disease. Twenty-three patients with radiographically diagnosed knee OA and 20 physically active adults performed stair ascending trials without support at their self-selected speed. Standard gait analysis was used to calculate three-dimensional lower extremity joint kinematics and kinetics. Forward trunk lean, or trunk flexion, was defined as the sagittal plane projection of the angle between a line connecting the midpoint of the trans-acromion line and the midpoint of the trans-iliac crest line and the global vertical axis. Patients with more severe knee OA (KL >or= 3) had greater forward trunk lean (+6.3 degrees , p = 0.045) and lower knee net quadriceps moments (-35.2%, p = 0.001) than controls. In more severe patients, the forward trunk lean was correlated with a reduction in the net quadriceps moment during stair climbing (R(2) = 0.590, p = 0.006). The results of this study identified a distinctive compensatory pattern of movement to reduce the quadriceps demand during stair climbing in patients with more severe knee OA by increasing forward trunk lean. Assessing forward trunk lean during stair climbing may be a useful functional marker for evaluating osteoarthritis status and quadriceps function that appears to be a more sensitive indicator of disease severity than perceived pain.

    View details for DOI 10.1002/jor.20751

    View details for Web of Science ID 000263307200007

    View details for PubMedID 18853434

  • Posturographic analysis through markerless motion capture without ground reaction forces measurement JOURNAL OF BIOMECHANICS Corazza, S., Andriacchi, T. R. 2009; 42 (3): 370-374

    Abstract

    The ability of the central nervous system to control posture and balance has been used with increasing frequency for the diagnosis and/or treatment evaluation of various neuromuscular diseases. Typically this analysis (Posturographic Analysis) is based on tracking the motion of the center of mass (COM) during quiet standing, however direct measurement of the COM has been commonly approximated using the movement of the center of pressure (COP). The purpose of this study was to apply and validate a new method to track the COM (center of mass) and COP (center of pressure) from a visual hull measured using a markerless motion capture (MMC) method. The method was tested by comparing the calculation of the COP from direct measurements of the COP. The deviations between the methods, below 2mm, were small relative to the average range of movement guaranteeing a satisfactory signal to noise ratio. This new method requires only kinematic data through MMC method and without the need of a force plate can identify the influence of individual body segments to motion of the COM.

    View details for DOI 10.1016/j.jbiomech.2008.11.019

    View details for Web of Science ID 000263657600029

    View details for PubMedID 19147143

  • The effect of isolated valgus moments on ACL strain during single-leg landing: A simulation study JOURNAL OF BIOMECHANICS Shin, C. S., Chaudhari, A. M., Andriacchi, T. P. 2009; 42 (3): 280-285

    Abstract

    Valgus moments on the knee joint during single-leg landing have been suggested as a risk factor for anterior cruciate ligament (ACL) injury. The purpose of this study was to test the influence of isolated valgus moment on ACL strain during single-leg landing. Physiologic levels of valgus moments from an in vivo study of single-leg landing were applied to a three-dimensional dynamic knee model, previously developed and tested for ACL strain measurement during simulated landing. The ACL strain, knee valgus angle, tibial rotation, and medial collateral ligament (MCL) strain were calculated and analyzed. The study shows that the peak ACL strain increased nonlinearly with increasing peak valgus moment. Subjects with naturally high valgus moments showed greater sensitivity for increased ACL strain with increased valgus moment, but ACL strain plateaus below reported ACL failure levels when the applied isolated valgus moment rises above the maximum values observed during normal cutting activities. In addition, the tibia was observed to rotate externally as the peak valgus moment increased due to bony and soft-tissue constraints. In conclusion, knee valgus moment increases peak ACL strain during single-leg landing. However, valgus moment alone may not be sufficient to induce an isolated ACL tear without concomitant damage to the MCL, because coupled tibial external rotation and increasing strain in the MCL prevent proportional increases in ACL strain at higher levels of valgus moment. Training that reduces the external valgus moment, however, can reduce the ACL strain and thus may help athletes reduce their overall ACL injury risk.

    View details for DOI 10.1016/j.jbiomech.2008.10.031

    View details for Web of Science ID 000263657600013

    View details for PubMedID 19100550

  • REGIONAL CARTILAGE THINNING OCCURS FIRST IN THE WALKING WEIGHT BEARING REGIONS OF THE FEMUR IN MEDIAL COMPARTMENT KNEE OSTEOARTHRITIS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE 2008, PTS A AND B Erhart, J. C., Muendermann, A., Koo, S., Merrick, B., Deagon, A., Giori, N. J., Andriacchi, T. P. 2009: 835-836
  • REDUCTION IN THE MEDIAL COMPARTMENT FORCE CORRELATES WITH THE REDUCTION IN KNEE ADDUCTION MOMENT USING A VARIABLE-STIFFNESS SHOE WITH AN INSTRUMENTED KNEE PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Erhart, J. C., Dyrby, C., D'Lima, D. D., Colwell, C. W., Andriacchi, T. P. 2009: 937-938
  • COMPARISON OF NUMERICALLY MODELED KNEE JOINT CONTACT FORCES TO INSTRUMENTED TOTAL KNEE PROSTHESIS FORCES PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Lundberg, H. J., Foucher, K. C., Andriacchi, T. P., Wimmer, M. A. 2009: 379-380
  • REGIONAL VARIATIONS IN CARTILAGE MECHANICS AND COMPOSITION SUGGEST A SENSITIVITY TO CHANGES IN CHRONIC JOINT LOADING PATTERNS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Bevill, S. L., Andriacchi, T. P. 2009: 279-280
  • CHANGES IN TIBIOFEMORAL KINEMATICS AND KINETICS DURING STAIR ASCENT AFTER PARTIAL MEDIAL MENISCECTOMY PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE 2008, PTS A AND B Netravali, N. A., Andriacchi, T. P. 2009: 813-814
  • ASSESSING THE APPROPRIATE NUMBER OF DAYS NEEDED TO APPROXIMATE PHYSICAL ACTIVITY LEVEL IN THE ACTIVE ELDERLY PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Rylander, J. H., Boyer, K. A., Andriacchi, T. P., Beaupre, G. S. 2009: 1101-1102
  • A RIGID BODY AND SPRING MODEL OF THE LUMBAR SPINE WHICH CONSIDERS THE MECHANICAL LOADS AT THE BONE-SCREW INTERFACE PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Kiriyama, Y., Matsumoto, M., Toyama, Y., Andriacchi, T. P., Nagura, T. 2009: 1241-1242
  • AN AUTOMATED IMAGE-BASED METHOD OF 3D SUBJECT SPECIFIC BODY SEGMENT PARAMETER ESTIMATION PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE 2008, PTS A AND B Sheets, A. L., Corazza, S., Andriacchi, T. 2009: 857-858
  • INTER-SUBJECT VARIABILITY IN GROUND REACTION FORCE - WALKING SPEED RELATIONSHIP IS RELATED TO DIFFERENT MOTION OF THE CENTER OF MASS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Boyer, K., Rylander, J., Andriacchi, T., Beaupre, G. 2009: 31-32
  • DYNAMIC COMPRESSION IN THE PRESENCE OF TNF-ALPHA DIFFERENTIALLY EFFECTS GENE EXPRESSION IN TIBIAL PLATEAU CARTILAGE COVERED AND UNCOVERED BY THE MENISCUS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE 2008, PTS A AND B Bevill, S. L., Andriacchi, T. P. 2009: 815-816
  • KINEMATIC DIFFERENCES BETWEEN THE FLAT, KICK AND SLICE SERVES MEASURED USING A MARKERLESS MOTION CAPTURE METHOD PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Sheets, A. L., Corazza, S., Abrams, G., Safran, M., Andriacchi, T. 2009: 195-196
  • STEP-TO-STEP VARIABILITY IN TIBIOFEMORAL CONTACT FORCE DURING WALKING MEASURED BY AN INSTRUMENTED KNEE IMPLANT PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Scanlan, S. F., D'Lima, D. D., Colwell, C. W., Andriacchi, T. P. 2009: 907-908
  • MENISCAL MOVEMENT DURING THE GAIT CYCLE IS SENSITIVE TO THE ATTACHMENT PROPERTIES OF THE MENISCAL HORNS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Netravali, N. A., Giori, N. J., Andriacchi, T. P. 2009: 981-982
  • Gender differences exist in the hip joint moments of healthy older walkers JOURNAL OF BIOMECHANICS Boyer, K. A., Beaupre, G. S., Andriacchi, T. P. 2008; 41 (16): 3360-3365

    Abstract

    Gender differences in the incidence of symptomatic hip osteoarthritis (OA), changes in hip cartilage volume and hip joint space and rates hip arthroplasty of older people are reported in the literature. As the rate of progression of OA is in part mechanically modulated it is possible that this gender bias may be related to inherent differences (if they exist) in walking mechanics between older males and females. The purpose of this study was to examine potential mechanisms for gender differences in hip joint mechanics during walking by testing the hypotheses that females would exhibit higher hip flexion, adduction and internal rotation moments but not significantly greater normalized ground reaction forces (GRFs). Forty-two healthy subjects (21 male, 21 female), ages 50-79yr were recruited for gait analysis. In support of the hypotheses, greater external hip adduction and internal rotation along with hip extension moments were found for females compared to males after normalizing for body size for all self-selected walking speeds. Differences in walking style (kinematics) were the main determinants in the joint kinetic differences as no differences in the normalized GRFs were found. As external joint moments are surrogate measures of the joint contact forces, the results of this study suggest the hip joint stress for the female population is higher compared to male population. This is in favor of a hypothesis that the increased joint contact stress in a female population could contribute to a greater joint degeneration at the hip in females as compared with males.

    View details for DOI 10.1016/j.jbiomech.2008.09.030

    View details for Web of Science ID 000261965300010

    View details for PubMedID 19022448

  • A comparison of measuring mechanical axis alignment using three-dimensional position capture with skin markers and radiographic measurements in patients with bilateral medial compartment knee osteoarthritis KNEE Muendermann, A., Dyrby, C. O., Andriacchi, T. P. 2008; 15 (6): 480-485

    Abstract

    The mechanical axis alignment of the lower extremity is typically measured from frontal plane radiographs of the entire lower extremity during double support standing. The purpose of this study was to test the hypothesis that the mechanical axis alignment can be predicted from skin markers on anatomical landmarks and anthropometric measurements and a stereophotogrammetric system based on significant correlation with the mechanical axis alignment measured from standing radiographs. Mechanical axis alignment was measured using full-limb radiographs for both knees of 62 patients with bilateral medial compartment knee osteoarthritis (OA). Mechanical axis alignment was also measured using a stereophotogrammetric system with markers on anatomical landmarks and anthropometric measurements to determine joint centers. The mechanical axis alignment from position capture correlated with that from radiographs (R(2)=0.544; P<0.001). This relationship did not depend on age, gender, BMI, or OA severity. A small but significant difference in the mechanical axis alignment between the two methods was observed (radiograph: 2.6 varus; position capture: 3.8 varus; P=0.001). Associations between mechanical axis alignment and OA severity were found for both methods (radiographic: R(2)=0.563; position capture: R(2)=0.807). The proposed method allows the measurement of the mechanical axis alignment without exposure to radiation. This method enables the establishment of the relationship between lower limb alignment and functional variables such as dynamic joint loading in degenerative joint disease and joint injury even in populations who typically do not undergo radiographic examination.

    View details for DOI 10.1016/j.knee.2008.07.002

    View details for Web of Science ID 000261547700009

    View details for PubMedID 18762426

  • Predicting changes in knee adduction moment due to load-altering interventions from pressure distribution at the foot in healthy subjects JOURNAL OF BIOMECHANICS Erhart, J. C., Muendermann, A., Muendermann, L., Andriacchi, T. P. 2008; 41 (14): 2989-2994

    Abstract

    The purpose of this pilot study of healthy subjects was to determine if changes in foot pressure patterns associated with a lateral wedge can predict the changes in the knee adduction moment. We tested two hypotheses: (1) increases or decreases in the knee adduction moment and ankle eversion moment due to load-altering footwear interventions can be predicted from foot pressure distribution and (2) changes in magnitude of the knee adduction moment and ankle eversion moment due to lateral wedges can be predicted from pressure distribution at the foot during walking. Fifteen healthy adults performed walking trials in three shoes: 0 degrees , 4 degrees , and 8 degrees laterally wedged. Maximum heel pressure ratio, first peak knee adduction moment, and peak ankle eversion moment were assessed using a pressure mat, motion capture system, and force plate. Increases or decreases in the knee adduction moment and ankle eversion moment were predicted well from foot pressure distribution. However, the magnitude of the pressure change did not predict the magnitude of the peak knee adduction moment change or peak ankle eversion moment change. Factors such as limb alignment or trunk motion may affect the knee adduction moment and override a direct relationship between the pressure distribution at the shoe-ground interface and the load distribution at the knee. However, changes (increases or decreases) in the peak knee adduction moment due to load-altering footwear interventions predicted from pressure distribution during walking can be important when evaluating these types of interventions from a clinical perspective.

    View details for DOI 10.1016/j.jbiomech.2008.07.021

    View details for Web of Science ID 000260985700014

    View details for PubMedID 18771767

  • In vivo knee loading characteristics during activities of daily living as measured by an instrumented total knee replacement JOURNAL OF ORTHOPAEDIC RESEARCH Muendermann, A., Dyrby, C. O., D'Lima, D. D., Colwell, C. W., Andriacchi, T. P. 2008; 26 (9): 1167-1172

    Abstract

    We examined the relationship between activity, peak load, medial to lateral load distribution, and flexion angle at peak load for activities of daily living. An instrumented knee prosthesis was used to measure knee joint force simultaneously with motion capture during walking, chair sit to stand and stand to sit, stair ascending and descending, squatting from a standing position, and golf swings. The maximum total compressive load at the knee was highest during stair ascending and descending and lowest during rising from a chair. Maximum total compressive load occurred at substantially different flexion angles ranging from 8.5 degrees during walking to 91.8 degrees during squatting. For all activities, total compressive load exceeded 2 times body weight, and for most activities 2.5 times body weight. Most activities placed a greater load on the medial compartment than the lateral compartment. Activities were grouped into three categories: high cycle loading (walk), high load (stair ascent, descent, and golf), and high flexion angle (chair sit to stand/stand to sit, and squat). The results demonstrate that the forces and motion sustained by the knee are highly activity-dependent and that the unique loading characteristics for specific activities should be considered for the design of functional and robust total knee replacements, as well as for rehabilitation programs for patients with knee osteoarthritis or following total knee arthroplasty.

    View details for DOI 10.1002/jor.20655

    View details for Web of Science ID 000258240300001

    View details for PubMedID 18404700

  • A variable-stiffness shoe lowers the knee adduction moment in subjects with symptoms of medial compartment knee osteoarthritis. Journal of biomechanics Erhart, J. C., Mündermann, A., Elspas, B., Giori, N. J., Andriacchi, T. P. 2008; 41 (12): 2720-2725

    Abstract

    The purpose of this study was to evaluate the effectiveness of variable-stiffness shoes in lowering the peak external knee adduction moment during walking in subjects with symptomatic medial compartment knee osteoarthritis. The influence on other lower extremity joints was also investigated. The following hypotheses were tested: (1) variable-stiffness shoes will lower the knee adduction moment in the symptomatic knee compared to control shoes; (2) reductions in knee adduction moment will be greater at faster speeds; (3) subjects with higher initial knee adduction moments in control shoes will have greater reductions in knee adduction moment with the intervention shoes; and (4) variable-stiffness shoes will cause secondary changes in the hip and ankle frontal plane moments. Seventy-nine individuals were tested at self-selected slow, normal, and fast speeds with a constant-stiffness control shoe and a variable-stiffness intervention shoe. Peak moments for each condition were assessed using a motion capture system and force plate. The intervention shoes reduced the peak knee adduction moment compared to control at all walking speeds, and reductions increased with increasing walking speed. The magnitude of the knee adduction moment prior to intervention explained only 11.9% of the variance in the absolute change in maximum knee adduction moment. Secondary changes in frontal plane moments showed primarily reductions in other lower extremity joints. This study showed that the variable-stiffness shoe reduced the knee adduction moment in subjects with medial compartment knee osteoarthritis without the discomfort of a fixed wedge or overloading other joints, and thus can potentially slow the progression of knee osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2008.06.016

    View details for PubMedID 18675981

  • The knee joint center of rotation is predominantly on the lateral side during normal walking JOURNAL OF BIOMECHANICS Koo, S., Andriacchi, T. P. 2008; 41 (6): 1269-1273

    Abstract

    The purpose of this study was to test the hypothesis of whether the center of rotation (COR) in the transverse plane of the knee is in the medial side during normal walking in a manner similar to that previously described during non-ambulatory activities. The kinematics for normal knees was obtained from 46 knees during normal walking using the point cluster technique. The COR of the medial-lateral axis of the femur relative to the tibia was determined during the stance phase of walking. The hypothesis that the COR is in the medial side during stance was not supported by this study. The average COR during the stance phase of walking was in the lateral compartment for all 46 knees. In addition, the instantaneous COR occurred on the medial side on average <25% of the time during the stance phase. Thus, while the COR is predominantly on the lateral side of the knee during walking, the normal function of the knee during walking is associated with both lateral and medial pivoting. These results also demonstrate the importance of describing knee kinematics in the context of a specific activity or the constraints of the test conditions.

    View details for Web of Science ID 000255674700015

    View details for PubMedID 18313060

  • Implications of increased medio-lateral trunk sway for ambulatory mechanics JOURNAL OF BIOMECHANICS Muendermann, A., Asay, J. L., Muendermann, L., Andriacchi, T. P. 2008; 41 (1): 165-170

    Abstract

    The purposes of this study was to test a mechanism to reduce the knee adduction moment by testing the hypothesis that increased medio-lateral trunk sway can reduce the knee adduction moment during ambulation in healthy subjects, and to examine the possibility that increasing medio-lateral trunk sway can produce similar potentially adverse secondary gait changes previously associated with reduced knee adduction moments in patients with knee osteoarthritis. Nineteen healthy adults performed walking trials with normal and increased medio-lateral trunk sway at a self-selected normal walking speed. Standard gait analysis was used to calculate three-dimensional lower extremity joint kinematics and kinetics. Knee and hip adduction moments were lower (-65.0% and -57.1%, respectively) for the increased medio-lateral trunk sway trials than for the normal trunk sway trials. Knee flexion angle at heel-strike was 3 degrees higher for the increased than for the normal trunk sway trials. Knee and hip abduction moments were higher for the increased medio-lateral trunk sway trials, and none of the other variables differed between the two conditions. Walking with increased medio-lateral trunk sway substantially reduces the knee adduction moment during walking in healthy subjects without some of the adverse secondary effects such as increased axial loading rates at the major joints of the lower extremity. This result supports the potential of using gait retraining for walking with increased medio-lateral trunk sway as treatment for patients with degenerative joint disease such as medial compartment knee osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2007.07.001

    View details for Web of Science ID 000253062100021

    View details for PubMedID 17678933

  • The patella ligament insertion angle influences quadriceps usage during walking of anterior cruciate ligament deficient patients JOURNAL OF ORTHOPAEDIC RESEARCH Shin, C. S., Chaudhari, A. M., Dyrby, C. O., Andriacchi, T. P. 2007; 25 (12): 1643-1650

    Abstract

    Following ACL injury a reduction in the peak knee flexion moment during walking (thought to be created by a decrease of quadriceps contraction) has been described as an adaptation to reduce anterior tibial translation (ATT) relative to the femur. However, the amount of ATT caused by quadriceps contraction is influenced by the patellar ligament insertion angle (PLIA). The purpose of this study was to test the hypothesis that quadriceps usage during walking correlates to individual anatomical variations in the extensor mechanism as defined by PLIA. PLIA and gait were measured for ACL-deficient knees, using subjects' contralateral knees as controls. In ACL-deficient knees, PLIA was negatively correlated (R2 = 0.59) to peak knee flexion moment (balanced by net quadriceps moment), while no correlation was found in contralateral knees. Reduction in peak flexion moment in ACL-deficient knees compared to their contralateral knees was distinctive in subjects with large PLIA, possibly to avoid excessive ATT. These results suggest that subject-specific anatomic variability of knee extensor mechanism may account for the individual variability previously observed in adaptation to a quadriceps reduction strategy following ACL injury. The average (+/-1 SD) PLIA of ACL-deficient knees (21.1 +/- 3.4 degrees) was less than the average PLIA of contralateral knees (23.9 +/- 3.1 degrees). This altered equilibrium position of the tibiofemoral joint associated with reduced PLIA and adaptations of gait patterns following ACL injury may be associated with degenerative changes in the articular cartilage. In the future, individually tailored treatment and rehabilitation considering individuals' specific extensor anatomy may improve clinical outcomes.

    View details for Web of Science ID 000251179300013

    View details for PubMedID 17593539

  • Knee and hip loading patterns at different phases in the menstrual cycle - Implications for the gender difference in anterior cruciate ligament injury rates AMERICAN JOURNAL OF SPORTS MEDICINE Chaudhari, A. M., Lindenfeld, T. N., Andriacchi, T. P., Hewett, T. E., Riccobene, J., Myer, G. D., Noyes, F. R. 2007; 35 (5): 793-800

    Abstract

    Menstrual cycle phase has been correlated with risk of noncontact anterior cruciate ligament injury in women. The mechanism by which hormonal cycling may affect injury rate is unknown.Jumping and landing activities performed during different phases of the menstrual cycle lead to differences in foot strike knee flexion, as well as peak knee and hip loads, in women not taking an oral contraceptive but not in women taking an oral contraceptive. Women will experience greater normalized joint loads than men during these activities.Controlled laboratory study.Twenty-five women (13 using oral contraceptives) and 12 men performed repeated trials of a horizontal jump, vertical jump, and drop from a 30-cm box on the left leg. Lower limb kinematics (foot strike knee flexion) and peak externally applied moments were calculated (hip adduction moment, hip internal rotation moment, knee flexion moment, knee abduction moment). Men were tested once. Women were tested twice for each phase of the menstrual cycle (follicular, luteal, ovulatory), as determined from serum analysis. An analysis of variance was used to examine differences between phases of the menstrual cycle and between groups (alpha = .05).No significant differences in moments or knee angle were observed between phases in either female group or between the 2 female groups or between either female group and the male controls.Variations of the menstrual cycle and the use of an oral contraceptive do not affect knee or hip joint loading during jumping and landing tasks.Because knee and hip joint loading is unaffected by cyclic variations in hormone levels, the observed difference in injury rates is more likely attributable to persistent differences in strength, neuromuscular coordination, or ligament properties.

    View details for DOI 10.1177/0363546506297537

    View details for Web of Science ID 000246264600013

    View details for PubMedID 17307891

  • In healthy subjects without knee osteoarthritis, the peak knee adduction moment influences the acute effect of shoe interventions designed to reduce medial compartment knee load JOURNAL OF ORTHOPAEDIC RESEARCH Fisher, D. S., Dyrby, C. O., Mundermann, A., Morag, E., Andriacchi, T. P. 2007; 25 (4): 540-546

    Abstract

    The purpose of this study was to evaluate shoe sole material stiffness changes and angle changes that are intended to reduce the peak knee adduction moment during walking. Fourteen physically active adults were tested wearing their personal shoes (control) and five intervention pairs, two with stiffness variations, two with angle variations, and a placebo shoe. The intervention shoes were evaluated based on how much they reduced the peak knee adduction moment compared to the control shoe. An ANOVA test was used to detect differences between interventions. Linear regression analysis was used to determine a relationship between the magnitude of the knee adduction moment prior to intervention and the effectiveness of the intervention in reducing the peak knee adduction moment. Peak knee adduction moments were reduced for the altered stiffness and altered angle shoes (p < 0.010), but not for the placebo shoe (p = 0.363). Additionally, linear regression analysis showed that subjects with higher knee adduction moments prior to intervention had larger reductions in the peak knee adduction moment (p < 0.010). These results demonstrate that shoe sole stiffness and angle interventions can be used to reduce the peak knee adduction moment and that subjects with initially higher peak knee adduction moments have higher reductions in their peak knee adduction moments.

    View details for DOI 10.1002/jor.20157

    View details for Web of Science ID 000245063900015

    View details for PubMedID 17205556

  • Clinical disability in posterior cruciate ligament deficient patients does not relate to knee laxity, but relates to dynamic knee function during stair descending KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY Iwata, S., Suda, Y., Nagura, T., Matsumoto, H., Otani, T., Andriacchi, T. P., Toyama, Y. 2007; 15 (4): 335-342

    Abstract

    We investigated the factors which influence clinical subjective symptoms during activities in Posterior cruciate ligament (PCL) deficient patients by evaluating knee laxity, muscle strength and knee mechanics during level walking, stair ascent and descent. Twenty-two subjects with isolated PCL deficient knees and 20 healthy volunteers were involved. The PCL deficient patients were divided into two subgroups based on previous history of experiencing giving-way during stair descent; a giving-way group (10 subjects) and a nongiving-way group (12 subjects). Giving-way during activities of daily living is a key symptom in isolated PCL deficient patients. No statistically significant differences in the knee laxity, muscle strength and knee mechanics during level walking and were observed between the giving-way group and the nongiving-way group. However, we found significant differences in the knee mechanics during stair ascent and descent between the two groups, and these differences were more remarkable during stair descent. Peak values of knee flexion angle, external knee flexion moment and posterior knee force during early stance phase were significantly lower in the giving-way group than in the nongiving-way group. This study indicated that the symptom of giving-way during stair descent was related to knee mechanics during stair descent, unlike other quantitative evaluations such as KT-2000 or Biodex.

    View details for DOI 10.1007/s00167-006-0198-3

    View details for Web of Science ID 000245431300004

    View details for PubMedID 16972109

  • Clinical disability in posterior cruciate ligament deficient patients does not relate to knee laxity, but relates to dynamic knee function during stair descending KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY Iwata, S., Suda, Y., Nagura, T., Matsumoto, H., Otani, T., Andriacchi, T. P., Toyama, Y. 2007; 15 (3): 258-265

    Abstract

    We investigated the factors which influence clinical subjective symptoms during activities in PCL deficient patients by evaluating knee laxity, muscle strength and knee mechanics during level walking, stair ascent and descent. Twenty-two subjects with isolated PCL deficient knees and 20 healthy volunteers were involved. The PCL deficient patients were divided into two subgroups based on previous history of experiencing giving-way during stair descent; a giving-way group (10 subjects) and a non giving-way group (12 subjects). Giving-way during activities of daily living is a key symptom in isolated PCL deficient patients. No statistically significant differences in the knee laxity, muscle strength and knee mechanics during level walking and were observed between the giving-way group and the non giving-way group. However, we found significant differences in the knee mechanics during stair ascent and descent between the two groups, and these differences were more remarkable during stair descent. Peak values of knee flexion angle, external knee flexion moment and posterior knee force during early stance phase were significantly lower in the giving-way group than in the non giving-way group. This study indicated that the symptom of giving-way during stair descent was related to knee mechanics during stair descent, unlike other quantitative evaluations such as KT-2000 or Biodex.

    View details for DOI 10.1007/s00167-006-0183-x

    View details for Web of Science ID 000245842200008

    View details for PubMedID 16967199

  • Quantifying variations in collagen matrix deformation in loaded articular cartilage PROCEEDING OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2007 Briant, P., Bevill, S., Andriacchi, T. P. 2007: 931-932
  • Accurately measuring human movement using articulated ICP with soft-joint constraints and a repository of articulated models 2007 IEEE CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION, VOLS 1-8 Mundermann, L., Corazza, S., Andriacchi, T. P. 2007: 2550-2555
  • The influence of deceleration forces on ACL strain during single-leg landing: A simulation study JOURNAL OF BIOMECHANICS Shin, C. S., Chaudhari, A. M., Andriacchi, T. P. 2007; 40 (5): 1145-1152

    Abstract

    Anterior cruciate ligament (ACL) injury commonly occurs during single limb landing or stopping from a run, yet the conditions that influence ACL strain are not well understood. The purpose of this study was to develop, test and apply a 3D specimen-specific dynamic simulation model of the knee designed to evaluate the influence of deceleration forces during running to a stop (single-leg landing) on ACL strain. This work tested the conceptual development of the model by simulating a physical experiment that provided direct measurements of ACL strain during vertical impact loading (peak value 1294N) with the leg near full extension. The properties of the soft tissue structures were estimated by simulating previous experiments described in the literature. A key element of the model was obtaining precise anatomy from segmented MR images of the soft tissue structures and articular geometry for the tibiofemoral and patellofemoral joints of the knee used in the cadaver experiment. The model predictions were correlated (Pearson correlation coefficient 0.889) to the temporal and amplitude characteristic of the experimental strains. The simulation model was then used to test the balance between ACL strain produced by quadriceps contraction and the reductions in ACL strain associated with the posterior braking force. When posterior forces that replicated in vivo conditions were applied, the peak ACL strain was reduced. These results suggest that the typical deceleration force that occurs during running to a single limb landing can substantially reduce the strain in the ACL relative to conditions associated with an isolated single limb landing from a vertical jump.

    View details for DOI 10.1016/j.jbiomech.2006.05.004

    View details for Web of Science ID 000245565400022

    View details for PubMedID 16797556

  • A framework for the functional identification of joint centers using markerless motion capture, validation for the hip joint JOURNAL OF BIOMECHANICS Corazza, S., Muendermann, L., Andriacchi, T. 2007; 40 (15): 3510-3515

    Abstract

    The objective of the study was to develop a framework for the accurate identification of joint centers to be used for the calculation of human body kinematics and kinetics. The present work introduces a method for the functional identification of joint centers using markerless motion capture (MMC). The MMC system used 8 color VGA cameras. An automatic segmentation-registration algorithm was developed to identify the optimal joint center in a least-square sense. The method was applied to the hip joint center with a validation study conducted in a virtual environment. The results had an accuracy (6mm mean absolute error) below the current MMC system resolution (1cm voxel resolution). Direct experimental comparison with marker-based methods was carried out showing mean absolute deviations over the three anatomical directions of 11.9 and 15.3mm if compared with either a full leg or only thigh markers protocol, respectively. Those experimental results were presented only in terms of deviations between the two systems (marker-based and markerless) as no real gold standard was available. The methods presented in this paper provide an important enabling step towards the biomechanical and clinical applications of markerless motion capture.

    View details for DOI 10.1016/j.jbiomech.2007.05.029

    View details for Web of Science ID 000251342800026

    View details for PubMedID 17697684

  • A comparison of the influence of global functional loads vs. local contact anatomy on articular cartilage thickness at the knee JOURNAL OF BIOMECHANICS Koo, S., Andriacchi, T. P. 2007; 40 (13): 2961-2966

    Abstract

    Cartilage contact geometry, along with joint loading, can play an important role in determining local articular cartilage tissue stress. Thus individual variations in cartilage thickness can be associated with both individual variations in joint loading associated with activities of daily living as well as individual differences in the anatomy of the contacting surfaces of the joint. The purpose of this study was to isolate the relationship between cartilage thickness predicted by individual variations in contact surface geometry based on the radii of the femur and tibia vs. cartilage thickness predicted by individual variations in joint loading. Knee magnetic resonance (MR) images and the peak knee adduction moments during walking were obtained from 11 young healthy male subjects (age 30.5+/-5.1 years). The cartilage thicknesses and surface radii of the femoral and tibial cartilage were measured in the weight-bearing regions of the medial and lateral compartments of three-dimensional models from the MR images. The ratio of contact pressure between the medial and lateral compartments was calculated from the radii of tibiofemoral contact surface geometries. The results showed that the medial to lateral pressure ratios were not correlated with the medial to lateral cartilage thickness ratios. However, in general, pressure was higher in the lateral than medial compartments and cartilage was thicker in the lateral than medial compartments. The peak knee adduction moment showed a significant positive linear correlation with medial to lateral thickness ratio in both femur (R(2)=0.43,P<0.01) and tibia (R(2)=0.32,P<0.01). The results of this study suggest that the dynamics of walking is an important factor to describe individual differences in cartilage thickness for normal subjects.

    View details for DOI 10.1016/j.jbiomech.2007.02.005

    View details for Web of Science ID 000250277800017

    View details for PubMedID 17418219

  • Numerical and experimental analysis of articular chondrocyte deformation: Calibration of a multiscale finite element model PROCEEDING OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2007 Bevill, S. L., Briant, P. L., Andriacchi, T. P. 2007: 321-322
  • Tibiofemoral joint contact force in deep knee flexion and its consideration in knee osteoarthritis and joint replacement JOURNAL OF APPLIED BIOMECHANICS Nagura, T., Matsumoto, H., Kiriyama, Y., Chaudhari, A., Andriacchi, T. P. 2006; 22 (4): 305-313

    Abstract

    The aim of the study was to estimate the tibiofemoral joint force in deep flexion to consider how the mechanical load affects the knee. We hypothesize that the joint force should not become sufficiently large to damage the joint under normal contact area, but should become deleterious to the joint under the limited contact area. Sixteen healthy knees were analyzed using a motion capture system, a force plate, a surface electromyography, and a knee model, and then tibiofemoral joint contact forces were calculated. Also, a contact stress simulation using the contact areas from the literature was performed. The peak joint contact forces (M +/- SD) were 4566 +/- 1932 N at 140 degrees in rising from full squat and 4479 +/- 1478 N at 90 degrees in rising from kneeling. Under normal contact area, the tibiofemoral contact stresses in deep flexion were less than 5 MPa and did not exceed the stress to damage the cartilage. The contact stress simulation suggests that knee prosthesis having the contact area smaller than 200 mm2 may be problematic since the contact stress in deep flexion would become larger than 21 MPa, and it would lead damage or wear of the polyethylene.

    View details for Web of Science ID 000242264900007

    View details for PubMedID 17293627

  • The role of ambulatory mechanics in the initiation and progression of knee osteoarthritis CURRENT OPINION IN RHEUMATOLOGY Andriacchi, T. P., Muendermann, A. 2006; 18 (5): 514-518

    Abstract

    This review examines recent in-vivo studies of ambulation and discusses the fundamental role of mechanics of ambulation in the initiation and progression of osteoarthritis at the knee.Recent studies have supported earlier findings that a high adduction moment at the knee during ambulation was most frequently reported to influence the progression of medial compartment osteoarthritis. In contrast to previous findings in patients with osteoarthritis, recent work on healthy subjects reports that cartilage thickness increases with high ambulatory loads. Kinematic changes were associated with the initiation of osteoarthritis. Recent studies of subjects with high risk factors for knee osteoarthritis (obesity and anterior cruciate ligament injury) reported a relationship between kinematic changes during ambulation and the initiation of osteoarthritis at the knee. This review also contrasts the relative influence on osteoarthritis of knee mechanics measured during ambulatory and nonambulatory activities.The initiation of osteoarthritis occurs when healthy cartilage experiences some condition (traumatic or chronic) that causes kinematic changes during ambulation at the knee to shift the load-bearing contact location of the joint to a region not conditioned to the new loading. The rate of progression of osteoarthritis is associated with increased load during ambulation.

    View details for Web of Science ID 000240652900014

    View details for PubMedID 16896293

  • A markerless motion capture system to study musculoskeletal biomechanics: Visual hull and simulated annealing approach ANNALS OF BIOMEDICAL ENGINEERING Corazza, S., Mundermann, L., Chaudhari, A. M., Demattio, T., Cobelli, C., Andriacchi, T. P. 2006; 34 (6): 1019-1029

    Abstract

    Human motion capture is frequently used to study musculoskeletal biomechanics and clinical problems, as well as to provide realistic animation for the entertainment industry. The most popular technique for human motion capture uses markers placed on the skin, despite some important drawbacks including the impediment to the motion by the presence of skin markers and relative movement between the skin where the markers are placed and the underlying bone. The latter makes it difficult to estimate the motion of the underlying bone, which is the variable of interest for biomechanical and clinical applications. A model-based markerless motion capture system is presented in this study, which does not require the placement of any markers on the subject's body. The described method is based on visual hull reconstruction and an a priori model of the subject. A custom version of adapted fast simulated annealing has been developed to match the model to the visual hull. The tracking capability and a quantitative validation of the method were evaluated in a virtual environment for a complete gait cycle. The obtained mean errors, for an entire gait cycle, for knee and hip flexion are respectively 1.5 degrees (+/-3.9 degrees ) and 2.0 degrees (+/-3.0 degrees ), while for knee and hip adduction they are respectively 2.0 degrees (+/-2.3 degrees ) and 1.1 degrees (+/-1.7 degrees ). Results for the ankle and shoulder joints are also presented. Experimental results captured in a gait laboratory with a real subject are also shown to demonstrate the effectiveness and potential of the presented method in a clinical environment.

    View details for DOI 10.1007/s10439-006-9122-8

    View details for Web of Science ID 000238546800012

    View details for PubMedID 16783657

  • Comparison of quantitative cartilage measurements acquired on two 3.0T MRI systems from different manufacturers JOURNAL OF MAGNETIC RESONANCE IMAGING Kornaat, P. R., Koo, S., Andriacchi, T. P., Bloem, J. L., Gold, G. E. 2006; 23 (5): 770-773

    Abstract

    To investigate the comparability of two osteoarthritis (OA) surrogate endpoints--average cartilage thickness and cartilage volume--acquired from healthy volunteers on two 3.0T magnetic resonance imaging (MRI) systems from different manufacturers.Ten knees of five healthy volunteers were scanned on a 3.0T General Electric (GE) and a 3.0T Philips scanner using a fast three-dimensional fat-suppressed spoiled gradient (SPGR) imaging sequence. The acquisition parameters were optimized beforehand and were kept as comparable as possible on both scanners. For quantitative analysis, the average cartilage thickness and volume of the load-bearing regions of the femoral condyles were compared. Data were analyzed using a univariate repeated-measures analysis of variance (ANOVA) to examine the effects of position, condyle, and imaging system on the measurements.The average cartilage thickness and volume of the load-bearing regions of the femoral condyles did not differ between the two different 3.0T MRI systems (P > 0.05). There was no significant effect of position or condyle on the average cartilage thickness measurements (P > 0.05; range = 0.41-0.93) or cartilage volume (P > 0.05; range = 0.14-0.87).Two OA surrogate endpoints--average cartilage thickness and cartilage volume--acquired on two 3.0T MRI systems from different manufacturers are comparable.

    View details for DOI 10.1002/jmri.20561

    View details for Web of Science ID 000237124800023

    View details for PubMedID 16568430

  • The evolution of methods for the capture of human movement leading to markerless motion capture for biomechanical applications JOURNAL OF NEUROENGINEERING AND REHABILITATION Mundermann, L., Corazza, S., Andriacchi, T. P. 2006; 3

    Abstract

    Over the centuries the evolution of methods for the capture of human movement has been motivated by the need for new information on the characteristics of normal and pathological human movement. This study was motivated in part by the need of new clinical approaches for the treatment and prevention of diseases that are influenced by subtle changes in the patterns movement. These clinical approaches require new methods to measure accurately patterns of locomotion without the risk of artificial stimulus producing unwanted artifacts that could mask the natural patterns of motion. Most common methods for accurate capture of three-dimensional human movement require a laboratory environment and the attachment of markers or fixtures to the body's segments. These laboratory conditions can cause unknown experimental artifacts. Thus, our understanding of normal and pathological human movement would be enhanced by a method that allows the capture of human movement without the constraint of markers or fixtures placed on the body. In this paper, the need for markerless human motion capture methods is discussed and the advancement of markerless approaches is considered in view of accurate capture of three-dimensional human movement for biomechanical applications. The role of choosing appropriate technical equipment and algorithms for accurate markerless motion capture is critical. The implementation of this new methodology offers the promise for simple, time-efficient, and potentially more meaningful assessments of human movement in research and clinical practice. The feasibility of accurately and precisely measuring 3D human body kinematics for the lower limbs using a markerless motion capture system on the basis of visual hulls is demonstrated.

    View details for DOI 10.1186/1743-0003-3-6

    View details for Web of Science ID 000251218700001

    View details for PubMedID 16539701

  • Comment: effect of fatigue on knee kinetics and kinematics in stop-jump tasks. American journal of sports medicine Chaudhari, A. M., Andriacchi, T. P. 2006; 34 (2): 312-?

    View details for PubMedID 16423915

  • Measuring human movement for biomechanical applications using markerless motion capture THREE-DIMENSIONAL IMAGE CAPTURE AND APPLICATIONS VII Mundermann, L., Corazza, S., Chaudhari, A. M., Andriacchi, T. P., Sundaresan, A., Chellappa, R. 2006; 6056
  • Rotational changes at the knee after ACL injury cause cartilage thinning CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Andriacchi, T. P., Briant, P. L., Bevill, S. L., Koo, S. 2006: 39-44

    Abstract

    We examined the relationship between specific gait changes after anterior cruciate ligament injury and the progression of osteoarthritis at the knee. The study was done using a finite-element model derived from subject specific three-dimensional cartilage volumes created from magnetic resonance images. Cartilage thinning was predicted using an iterative algorithm based on the octahedral shear stress. Simulations were done for a knee with normal alignment and for a knee with an internal tibial rotation offset, as associated with anterior cruciate ligament deficiency. For the healthy knee, the model predicted patterns of cartilage thinning consistent with a previous clinical report of idiopathic osteoarthritis. For the ACL-deficient scenario the model predicted a more rapid rate of cartilage thinning throughout the knee, especially in the medial compartment. The results suggest that the progression of osteoarthritis after anterior cruciate ligament injury is associated with a shift in the normal load bearing regions of the knee joint during normal function due to kinematic changes, and highlight the importance of restoring proper gait during anterior cruciate ligament reconstruction.

    View details for DOI 10.1097/01.blo.0000197079.26600.09

    View details for Web of Science ID 000243019700008

    View details for PubMedID 16394737

  • The mechanical consequences of dynamic frontal plane limb alignment for non-contact ACL injury JOURNAL OF BIOMECHANICS Chaudhari, A. M., Andriacchi, T. P. 2006; 39 (2): 330-338

    Abstract

    This study investigated the mechanical consequences of differences in dynamic frontal plane alignment of the support limb and the influence of anticipatory muscle activation at the hip and ankle on reducing the potential for non-contact ACL injury during single-limb landing. A frontal plane, three-link passive dynamic model was used to estimate an ACL non-contact injury threshold. This threshold was defined as the maximum axial force that the knee could sustain before the joint opened 8 degrees either medially or laterally, which was deemed sufficient to cause injury. The limb alignment and hip and ankle muscle contractions were varied to determine their effects on the ACL injury threshold. Valgus or varus alignment reduced the injury threshold compared to neutral alignment, but increasing the anticipatory contraction of hip abduction and adduction muscle groups increased the injury threshold. Increasing anticipatory ankle inversion/eversion muscle contraction had no effect. This study provides a mechanical rationale for the conclusion that a neutral limb alignment (compared to valgus or varus) during landing and increasing hip muscle contraction (abductors/adductors) prior to landing can reduce the possibility of ACL rupture through a valgus or varus opening mechanism.

    View details for DOI 10.1016/j.jbiomech.2004.11.013

    View details for Web of Science ID 000234117900014

    View details for PubMedID 16321635

  • Considerations in measuring cartilage thickness using MRI: factors influencing reproducibility and accuracy OSTEOARTHRITIS AND CARTILAGE Koo, S., Gold, G. E., Andriacchi, T. P. 2005; 13 (9): 782-789

    Abstract

    The primary goal of this study was to describe and evaluate conditions that could influence the precision and accuracy of measuring in vivo cartilage thickness in the weight bearing regions of the knee from magnetic resonance imaging (MRI).Three-dimensional (3D) models of the femoral cartilage were created from segmented MR images. The weight bearing regions on femoral cartilage were selected for the portion of the tibiofemoral joint that sustains contact during walking. Six regions of interest (three on each condyle) were located on the femur. Average cartilage thickness was calculated over each region. The sensitivity of the precision of the measurements to observer variability was evaluated using intra- and inter-observer reproducibility tests of cartilage thickness measurements from the MRI-derived 3D models. In addition, the quantitative influence of a rule-based protocol for segmentation was evaluated using the inter-observer reproducibility protocol. Accuracy tests were conducted on porcine knees by comparing 3D models from MR images and laser scans across weight bearing and non-weight bearing regions.The precision was substantially better for the intra-observer tests (Coefficient of variation (CV) = 1-3%) than the inter-observer tests. Adding a rule-based protocol reduced variability in inter-observer tests substantially (CV = 6.6% vs 8.3%). Accuracy tests showed that the central and weight bearing regions on each condyle were more accurate than boundary and non-weight bearing regions. In addition, these results indicate that care should be taken when determining cartilage thickness of weight bearing regions with cartilage degenerations, since the thickness of thinner cartilage can be systematically overestimated in MR images.A rule-based approach can substantially increase inter-observer reproducibility when measuring cartilage thickness from multiple observers. This improvement in inter-observer reproducibility could be an important consideration for longitudinal studies of disease progression. In quantifying cartilage thickness, central and weight bearing regions on each condyle can provide more accurate measurement than boundary and non-weight bearing regions with average accuracy of +/-0.2-0.3 mm. An important finding of this study was that the weight bearing regions, which are usually of the greatest clinical interest, were measured most accurately by sagittal plane imaging.

    View details for DOI 10.1016/j.joca.2005.04.013

    View details for Web of Science ID 000232252100005

    View details for PubMedID 15961328

  • Secondary gait changes in patients with medial compartment knee osteoarthritis - Increased load at the ankle, knee, and hip during walking ARTHRITIS AND RHEUMATISM Mundermann, A., Dyrby, C. O., Andriacchi, T. P. 2005; 52 (9): 2835-2844

    Abstract

    This study tested the hypothesis that gait changes related to knee osteoarthritis (OA) of varied severity are associated with increased loads at the ankle, knee, and hip.Forty-two patients with bilateral medial compartment knee OA and 42 control subjects matched for sex, age, height, and mass were studied. Nineteen patients had Kellgren/Lawrence (K/L) radiographic severity grades of 1 or 2, and 23 patients had K/L grades of 3 or 4. Three-dimensional kinematics and kinetics were measured in the hip, knee, and ankle while the subjects walked at a self-selected speed.Patients with more severe knee OA had greater first peak knee adduction moments than their matched control subjects (P = 0.039) and than patients with less severe knee OA (P < 0.001). All patients with knee OA made initial contact with the ground with the knee in a more extended position than that exhibited by control subjects. An increased axial loading rate was present in all joints of the lower extremity. Patients with more severe knee OA had lower hip adduction moments compared with their matched control subjects.The secondary gait changes observed among patients with knee OA reflect a potential strategy to shift the body's weight more rapidly from the contralateral limb to the support limb, which appears to be successful in reducing the load at the knee in only patients with less severe knee OA. The increased loading rate in the lower extremity joints may lead to a faster progression of existing OA and to the onset of OA at joints adjacent to the knee. Interventions for knee OA should therefore be assessed for their effects on the mechanics of all joints of the lower extremity.

    View details for DOI 10.1002/art.21262

    View details for Web of Science ID 000232115700031

    View details for PubMedID 16145666

  • The influence of slip velocity on wear of total knee arthroplasty WEAR Schwenke, T., Borgstede, L. L., Schneider, E., Andriacchi, T. P., Wimmer, M. A. 2005; 259: 926-932
  • Sport-dependent variations in arm position during single-limb landing influence knee loading - Implications for anterior cruciate ligament injury AMERICAN JOURNAL OF SPORTS MEDICINE Chaudhari, A. M., Hearn, B. K., Andriacchi, T. P. 2005; 33 (6): 824-830

    Abstract

    Increased valgus loading at the knee has been previously identified as a possible risk factor for noncontact anterior cruciate ligament injuries, which are common in sports. Arm position variation may affect risk of injury by altering valgus knee loading.Sport-dependent variations in arm position increase valgus loading of the knee during run-to-cut maneuvers.Controlled laboratory study.Eleven subjects performed a sidestep cutting maneuver, first with no arm constraints and then with 3 sports-related arm positions in random order (holding a lacrosse stick, holding a football on the plant side, and holding a football on the cut side). The analysis focused on the knee valgus moment relative to the arm positions during the landing phase of the activity.Arm position significantly influenced the valgus moment with an increase in the lacrosse trials and in the plant-side football trials but not in the cut-side football trials (alpha = .05).Constraining the plant-side arm results in increased valgus loading at the knee during run-to-cut maneuvers, which suggests the possibility of greater risk of anterior cruciate ligament injury during these conditions.These results suggest that training methods that consider arm position as a risk factor could help reduce the risk of anterior cruciate ligament noncontact injury.

    View details for DOI 10.1177/0363546504270455

    View details for Web of Science ID 000229314300004

    View details for PubMedID 15827366

  • MR imaging of articular cartilage at 1.5T and 3.0T: Comparison of SPGR and SSFP sequences OSTEOARTHRITIS AND CARTILAGE Kornaat, P. R., Reeder, S. B., Koo, S., Brittain, J. H., Yu, H., Andriacchi, T. P., Gold, G. E. 2005; 13 (4): 338-344

    Abstract

    To compare articular cartilage signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and thickness measurements on a 1.5 T and a 3.0 T magnetic resonance (MR) scanner using three-dimensional spoiled gradient recalled echo (3D-SPGR) and two 3D steady-state free precession (SSFP) sequences.Both knees of five volunteers were scanned at 1.5 T and at 3.0 T using a transmit-receive quadrature extremity coil. Each examination consisted of a sagittal 3D-SPGR sequence, a sagittal fat suppressed 3D-SSFP (FS-SSFP) sequence, and a sagittal Dixon 3D-SSFP sequence. For quantitative analysis, we compared cartilage SNR and CNR efficiencies, as well as average cartilage thickness measurements.For 3D-SPGR, cartilage SNR efficiencies at 3.0 T increased compared to those at 1.5 T by a factor of 1.83 (range: 1.40-2.09). In comparison to 3D-SPGR, the SNR efficiency of FS-SSFP increased by a factor of 2.13 (range: 1.81-2.39) and for Dixon SSFP by a factor of 2.39 (range: 1.95-2.99). For 3D-SPGR, CNR efficiencies between cartilage and its surrounding tissue increased compared to those at 1.5 T by a factor of 2.12 (range: 1.75-2.47), for FS-SSFP by a factor 2.11 (range: 1.58-2.80) and for Dixon SSFP by a factor 2.39 (range 2.09-2.83). Average cartilage thicknesses of load bearing regions were not different at both field strengths or between sequences (P>0.05). Mean average cartilage thickness measured in all knees was 2.28 mm.Articular cartilage imaging of the knee on a 3.0 T MR scanner shows increased SNR and CNR efficiencies compared to a 1.5 T scanner, where SSFP-based techniques show the highest increase in SNR and CNR efficiency. There was no difference between average cartilage thickness measurements performed at the 1.5 T and 3.0 T scanners or between the three different sequences.

    View details for DOI 10.1016/j.joca.2004.12.008

    View details for Web of Science ID 000228216200008

    View details for PubMedID 15780647

  • Interactions between kinematics and loading during walking for the normal and ACL deficient knee JOURNAL OF BIOMECHANICS Andriacchi, T. P., Dyrby, C. O. 2005; 38 (2): 293-298

    Abstract

    The relationships between extrinsic forces acting at the knee and knee kinematics were examined with the purpose of identifying specific phases of the walking cycle that could cause abnormal kinematics in the anterior cruciate ligament (ACL) deficient knee. Intersegmental forces and moments in directions that would produce anterior-posterior (AP) translation, internal-external (IE) rotation and flexion-extension (FE) at the knee were compared with the respective translation and rotations of the tibia relative to the femur during four selected phases (heel strike, weight acceptance, terminal extension and swing) of the walking cycle. The kinematic changes associated with loss of the ACL occurred primarily during the terminal portion of swing phase of the walking cycle where, for the ACL deficient knee, the tibia had reduced external rotation and anterior translation as the knee extended prior to heel strike. The kinematic changes during swing phase were associated with a rotational offset relative to the contralateral knee in the average position of the tibia towards internal rotation. The offset was maintained through the entire gait cycle. The abnormal offsets in the rotational position were correlated with the magnitude of the flexion moment (balanced by a net quadriceps moment) during weight acceptance. These results suggest that adaptations to the patterns of muscle firing during walking can compensate for kinematic changes associated with the loss of the ACL. The altered rotational position would cause changes in tibiofemoral contact during walking that could cause the type of degenerative changes reported in the meniscus and the articular cartilage following ACL injury.

    View details for DOI 10.1016/j.jbiomech.2004.02.010

    View details for Web of Science ID 000226463100012

    View details for PubMedID 15598456

  • Serum concentration of cartilage oligomeric matrix protein (COMP) is sensitive to physiological cyclic loading in healthy adults OSTEOARTHRITIS AND CARTILAGE Mundermann, A., Dyrby, C. O., Andriacchi, T. P., King, K. B. 2005; 13 (1): 34-38

    Abstract

    To test the hypothesis that physiological cyclic loading during a 30-min walking exercise causes an increase in serum cartilage oligomeric matrix protein (COMP) concentration in a healthy population.Blood samples (5 ml) were drawn from 10 physically active adults immediately before and after, and 0.5h, 1.5h, 3.5h and 5.5h after a 30-min walking exercise on a level outdoor walking track at self-selected normal speed. On a separate day, blood samples were drawn from the same 10 subjects during 6h while they were resting in a chair. Serum COMP concentrations were determined using a commercial enzyme-linked immunosorbent assay (COMP ELISA). An activity monitor was used to record basic time-distance measurements of gait. Serum COMP concentrations within the exercise protocol and within the resting protocol were compared using separate repeated measures analyses of variance (alpha=0.05).In the exercise protocol, a first increase (9.7%; P=0.003) occurred immediately after the walking exercise. A second increase in serum COMP concentration (7.0%; P=0.024) occurred 5.5h after the walking exercise. In the resting protocol, the concentration at baseline was significantly higher than at all subsequent time points (8.2%; P<0.050). Serum COMP concentration decreased from the 3.5-h to the 5.5-h sample (-4.8%; P=0.012).Even a moderate walking activity can significantly influence serum COMP concentration. The immediate response points to a diffusion time of COMP fragments from cartilage to the blood of 30 min or less. The response at 5.5h indicates a metabolic delay for COMP in the range of 5h to 6h.

    View details for DOI 10.1016/j.joca.2004.09.007

    View details for Web of Science ID 000226546700005

    View details for PubMedID 15639635

  • Most favorable camera configuration for a shape-from-silhouette markerless motion capture system for biomechanical analysis VIDEOMETRICS VIII Mundermann, L., Corazza, S., Chaudhari, A. M., Alexander, E. J., Andriacchi, T. P. 2005; 5665: 278-287
  • Conditions that influence the accuracy of anthropometric parameter estimation for human body segments using shape-from-silhouette VIDEOMETRICS VIII Mundermann, L., Mundermann, A., Chaudhari, A. M., Andriacchi, T. P. 2005; 5665: 268-277
  • The mechanobiology of articular cartilage development and degeneration CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Carter, D. R., Beaupre, G. S., Wong, M., Smith, R. L., Andriacchi, T. P., Schurman, D. J. 2004: S69-S77

    Abstract

    The development, maintenance, and destruction of cartilage are regulated by mechanical factors throughout life. Mechanical cues in the cartilage fetal endoskeleton influence the expression of genes that guide the processes of growth, vascular invasion, and ossification. Intermittent fluid pressure maintains the cartilage phenotype whereas mild tension (or shear) promotes growth and ossification. The articular cartilage thickness is determined by the position at which the subchondral growth front stabilizes. In mature joints, cartilage is thickest and healthiest where the contact pressure and cartilage fluid pressure are greatest. The depth-dependent histomorphology reflects the local fluid pressure, tensile strain, and fluid exudation. Osteoarthritis represents the final demise and loss of cartilage in the skeletal elements. The initiation and progression of osteoarthritis can follow many pathways and can be promoted by mechanical factors including: (1) reduced loading, which activates the subchondral growth front by reducing fluid pressure; (2) blunt impact, causing microdamage and activation of the subchondral growth front by local shear stress; (3) mechanical abnormalities that increase wear at the articulating surface; and (4) other mechanically related factors. Research should be directed at integrating our mechanical understanding of osteoarthritis pathogenesis and progression within the framework of cellular and molecular events throughout ontogeny.

    View details for DOI 10.1097/01.blo.0000144970.05107.7e

    View details for Web of Science ID 000224524400014

    View details for PubMedID 15480079

  • Secondary motions of the knee during weight bearing and non-weight bearing activities JOURNAL OF ORTHOPAEDIC RESEARCH Dyrby, C. O., Andriacchi, T. P. 2004; 22 (4): 794-800

    Abstract

    The objective of this study was to test the hypothesis that during a weight bearing activity such as walking, a dynamic range (envelope of motion) exists in the relationship between the secondary knee motions (anterior-posterior (AP) translation, internal-external (IE) rotation, and abduction-adduction (Ab-Adduction)) and knee flexion angle. In addition differences in the envelope of motion between a weight bearing and non-weight bearing activity were tested. The hypothesis was evaluated by testing for differences (offsets) in secondary displacements at specific knee flexion angles during the walking cycle and seated leg extension (non-weight bearing). Kinematic measurements were obtained using a previously developed point cluster technique to analyze the six-degrees of freedom movement of the knee. During walking, phase plots of the IE rotation and AP translation versus knee flexion demonstrated significant offsets from one phase of the gait cycle to another at the same flexion angle. During the non-weight bearing activity, no significant offset in the secondary movement was found; the knee followed the same pathway of motion during the flexion and extension phase of this activity. The characteristics of the secondary motions during walking indicated that secondary knee movements are caused by the external forces (muscle, inertial and gravitational) that act on the knee during the various phases of the walking cycle. The boundaries of the envelope appear to reflect the characteristics of the passive restraints. The weight bearing secondary motion AP and IE rotation seen during a walking activity demonstrated an envelope of dynamic laxity that could potentially be used to evaluate functional instabilities at the knee.

    View details for DOI 10.1016/j.orthres.2003.11.003

    View details for Web of Science ID 000222402000015

    View details for PubMedID 15183436

  • Functional evaluation of the Scandinavian Total Ankle Replacement FOOT & ANKLE INTERNATIONAL Dyrby, C., Chou, L. B., Andriacchi, T. P., Mann, R. A. 2004; 25 (6): 377-381

    Abstract

    The purpose of this study was to evaluate the function of the ankle joint during walking before and after Scandinavian Total Ankle Replacement (STAR). Nine patients (six males and three females) with an average age of 65 years, scheduled for unilateral total ankle replacement for osteoarthritis and rheumatoid arthritis, were evaluated both preoperatively and postoperatively in a gait analysis laboratory. Arthroplasty patients showed reduced range of motion at the ankle compared to normal controls. Postoperative arthroplasty subjects had significantly improved external ankle dorsiflexion moment, the moment that affects the plantarflexor muscles, when compared to their preoperative status. The moment in arthroplasty patients was increased, indicating improved function of the ankle joint.

    View details for Web of Science ID 000223885900002

    View details for PubMedID 15215020

  • Potential strategies to reduce medial compartment loading in patients with knee osteoarthritis of varying severity - Reduced walking speed ARTHRITIS AND RHEUMATISM Mundermann, A., Dyrby, C. O., Hurwitz, D. E., Sharma, L., Andriacchi, T. P. 2004; 50 (4): 1172-1178

    Abstract

    To determine whether reducing walking speed is a strategy used by patients with knee osteoarthritis (OA) of varying disease severity to reduce the maximum knee adduction moment.Self-selected walking speeds and maximum knee adduction moments of 44 patients with medial tibiofemoral OA of varying disease severity, as assessed by using the Kellgren/Lawrence grade, were compared with those of 44 asymptomatic control subjects matched for sex, age, height, and weight.Differences in self-selected normal walking speed explained only 8.9% of the variation in maximum knee adduction moment for the group of patients with knee OA. The severity of the disease influenced the adduction moment-walking speed relationship; the individual slopes of this relationship were significantly greater in patients with less severe OA than in asymptomatic matched control subjects. Self-selected walking speed did not differ between patients with knee OA, regardless of the severity, and asymptomatic control subjects. However, knees with more-severe OA had significantly greater adduction moments (mean +/- SD 3.80 +/- 0.89% body weight x height) and were in more varus alignment (6.0 +/- 4.5 degrees ) than knees with less-severe OA (2.94 +/- 0.70% body weight x height; and 0.0 +/- 2.9 degrees, respectively).Patients with less-severe OA adapt a walking style that differs from that of patients with more-severe OA and controls. This walking style is associated with the potential to reduce the adduction moment when walking at slower speeds and could be linked to decreased disease severity.

    View details for DOI 10.1002/art.20132

    View details for Web of Science ID 000220763600018

    View details for PubMedID 15077299

  • Sensitivity of finite helical axis parameters to temporally varying realistic motion utilizing an idealized knee model PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART H-JOURNAL OF ENGINEERING IN MEDICINE Johnson, T. S., Andriacchi, T. P., Erdman, A. G. 2004; 218 (H2): 89-100

    Abstract

    Various uses of the screw or helical axis have previously been reported in the literature in an attempt to quantify the complex displacements and coupled rotations of in vivo human knee kinematics. Multiple methods have been used by previous authors to calculate the axis parameters, and it has been theorized that the mathematical stability and accuracy of the finite helical axis (FHA) is highly dependent on experimental variability and rotation increment spacing between axis calculations. Previous research has not addressed the sensitivity of the FHA for true in vivo data collection, as required for gait laboratory analysis. This research presents a controlled series of experiments simulating continuous data collection as utilized in gait analysis to investigate the sensitivity of the three-dimensional finite screw axis parameters of rotation, displacement, orientation and location with regard to time step increment spacing, utilizing two different methods for spatial location. Six-degree-of-freedom motion parameters are measured for an idealized rigid body knee model that is constrained to a planar motion profile for the purposes of error analysis. The kinematic data are collected using a multicamera optoelectronic system combined with an error minimization algorithm known as the point cluster method. Rotation about the screw axis is seen to be repeatable, accurate and time step increment insensitive. Displacement along the axis is highly dependent on time step increment sizing, with smaller rotation angles between calculations producing more accuracy. Orientation of the axis in space is accurate with only a slight filtering effect noticed during motion reversal. Locating the screw axis by a projected point onto the screw axis from the mid-point of the finite displacement is found to be less sensitive to motion reversal than finding the intersection of the axis with a reference plane. A filtering effect of the spatial location parameters was noted for larger time step increments during periods of little or no rotation.

    View details for Web of Science ID 000221365400001

    View details for PubMedID 15116896

  • Non-rigid modeling of body segments for improved skeletal motion estimation CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES Alexander, E. J., Bregler, C., Andriacchi, T. P. 2003; 4 (3-4): 351-364
  • Self-reported giving-way episode during a stepping-down task: Case report of a subject with an ACL-deficient knee - Invited commentary JOURNAL OF ORTHOPAEDIC & SPORTS PHYSICAL THERAPY Andriacchi, T., Chaudhari, A. 2003; 33 (5): 283-284
  • The use of functional analysis in evaluating knee kinematics CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Andriacchi, T. P., Dyrby, C. O., Johnson, T. S. 2003: 44-53

    Abstract

    The importance of understanding the six-degrees-of-freedom kinematics of the knee during ambulatory activities was examined in the context of the function of total knee arthroplasty. Studies of knee kinematics during walking, stair climbing, and a deep flexion squat indicate that knee kinematics is activity-dependent. A comparative study of patients and healthy subjects during stair climbing indicates the importance of maintaining the function of the posterior cruciate ligament. A second study used walking kinematics derived from patient testing as input to a wear simulator. There was increased wear relative to standard simulator input that was related to the slip velocity at the contact surface. Finally, results from a study of deep flexion indicate that substantial femoral rotation is required during deep flexion activities. The current study shows the importance of studying in vivo knee kinematics for future enhancement in the treatment of the arthritic knee.

    View details for DOI 10.1097/01.blo.0000062383.79828.f5

    View details for Web of Science ID 000182630400007

    View details for PubMedID 12771816

  • A new parametric approach for modeling hip forces during gait JOURNAL OF BIOMECHANICS Hurwitz, D. E., Foucher, K. C., Andriacchi, T. P. 2003; 36 (1): 113-119

    Abstract

    An analytical parametric model was developed to estimate the natural biological variations in muscle forces and their effect on the hip forces subject only to physiological constraints and not predefined optimization criterion. Force predictions are based on the joint kinematics and kinetics of each subject, a previously published muscle model, and physiological constraints on the muscle force distributions. The model was used to determine the hip contact forces throughout the stance phase of gait of a subject with a total hip replacement (THR). The parametrically modeled peak hip force without antagonistic muscle activity varied from 2.7 to 3.2 Body Weights (mean 2.9 Body Weights), which agreed well with published in vivo measurements from instrumented THRs in other subjects. For every 10% increase in antagonistic activity, the mean peak hip force increased by 0.2 Body Weights. The parametric model allows one to examine the effect of specific muscle weaknesses or increased antagonistic muscle activity on the hip forces. The model also provides a tool for studying the effect of gait adaptations on hip forces, as predictions are based on each individual's gait data. Differences in peak forces between subjects can then be evaluated relative to the uncertainty in not knowing the precise muscle force distributions.

    View details for Web of Science ID 000180688700013

    View details for PubMedID 12485645

  • Comparison of clinical and dynamic knee function in patients with anterior cruciate ligament deficiency AMERICAN JOURNAL OF SPORTS MEDICINE Patel, R. R., Hurwitz, D. E., Bush-Joseph, C. A., Bach, B. R., Andriacchi, T. P. 2003; 31 (1): 68-74

    Abstract

    Whether passive measures of isokinetic muscle strength deficits and knee laxity are related to the dynamic function of the anterior cruciate ligament-deficient knee remains unclear.Arthrometer measurements are not predictive of peak external knee flexion moment (net quadriceps muscle moment), isokinetic quadriceps muscle strength correlates with peak external knee flexion moment (net quadriceps muscle moment), and isokinetic hamstring muscle strength correlates with peak external knee extension moment (net flexor muscle moment).Cross-sectional study.Gait analysis was used to assess dynamic function during walking, jogging, and stair climbing in 44 subjects with unilateral anterior cruciate ligament deficiency and 44 control subjects. Passive knee laxity and isokinetic quadriceps and hamstring muscle strength were also measured.Arthrometer measurements did not correlate with peak external flexion or extension moments in any of the activities tested or with isokinetic quadriceps or hamstring muscle strength. Test subjects also had a significantly reduced peak external flexion moment during all three jogging activities and stair climbing compared with the control subjects and this was correlated with significantly reduced quadriceps muscle strength.Absolute knee laxity difference did not correlate with dynamic knee function as assessed by gait analysis and should not be used as a sole predictor for the outcome of treatment. Patients with greater than normal strength in the anterior cruciate ligament-deficient limb performed low- and high-stress activities in a more normal fashion than those with normal or less-than-normal strength.

    View details for Web of Science ID 000180473300012

    View details for PubMedID 12531760

  • Risk factors for progressive cartilage loss in the knee: a longitudinal magnetic resonance imaging study in forty-three patients. Arthritis and rheumatism Biswal, S., Hastie, T., Andriacchi, T. P., Bergman, G. A., Dillingham, M. F., Lang, P. 2002; 46 (11): 2884-2892

    Abstract

    To evaluate the rate of progression of cartilage loss in the knee joint using magnetic resonance imaging (MRI) and to evaluate potential risk factors for more rapid cartilage loss.We evaluated baseline and followup MRIs of the knees in 43 patients (minimum time interval of 1 year, mean 1.8 years, range 52-285 weeks). Cartilage loss was graded in the anterior, central, and posterior regions of the medial and lateral knee compartments. Knee joints were also evaluated for other pathology. Data were analyzed using analysis of variance models.Patients who had sustained meniscal tears showed a higher average rate of progression of cartilage loss (22%) than that seen in those who had intact menisci (14.9%) (P

    View details for PubMedID 12428228

  • Backsurface wear and deformation in polyethylene tibial inserts retrieved postmortem CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Surace, M. F., Berzins, A., Urban, R. M., Jacobs, J. J., Berger, R. A., Natarajan, R. N., Andriacchi, T. P., Galante, J. O. 2002: 14-23

    Abstract

    Wear and deformation were characterized at the backsurface of 25 posterior cruciate-retaining total knee arthroplasty polyethylene inserts retrieved postmortem from 20 subjects. The mean implantation time was 64.1 months (range, 4-156 months). The backsurface of the inserts was inspected using a stereomicroscope with a digital optical system. Coronal histologic sections of 13 proximal tibias were inspected for the presence and extent of penetration of granuloma. Damage to the backsurface was limited. Polishing was recorded on 21 (84%) of the inserts and abrasive wear on five (20%) inserts. Pitting was present in 21 (84%) components, but involved less than 1% of the area in all but one of these components. Delamination and cracking were not observed. Extrusions were seen in all 10 of the components that had screw holes in the tibial tray. A correlation was found between the depth of penetration of the granuloma along the posteromedial screw and the height of the corresponding extrusion. The anteroposterior profiles showed a concave deformation of the backsurface in 24 (96 %) of the cases. The concave deformation of tibial inserts may facilitate accumulation and transportation of wear debris to the tibial bone-implant interface through the screw holes in implants designed for cementless fixation.

    View details for Web of Science ID 000179273100004

  • Mechanical loads at the knee joint during deep flexion JOURNAL OF ORTHOPAEDIC RESEARCH Nagura, T., Dyrby, C. O., Alexander, E. J., Andriacchi, T. P. 2002; 20 (4): 881-886

    Abstract

    There is a lack of fundamental information on the knee biomechanics in deep flexion beyond 90 degrees. In this study, mechanical loads during activities requiring deep flexion were quantified on normal knees from 19 subjects, and compared with those in walking and stair climbing. The deep flexion activities generate larger net quadriceps moments (6.9-13.5% body weight into height) and net posterior forces (58.3-67.8% body weight) than routine ambulatory activities. Moreover, the peak net moments and the net posterior forces were generated between 90 degrees and 150 degrees of flexion. The large moments and forces will result in high stress at high angles of flexion. These loads can influence pathological changes to the joint and are important considerations for reconstructive procedures of the knee. The posterior cruciate ligament should have a substantial role during deep flexion, since there was a large posterior load that must be sustained at the knee. The mechanics of the knee in deep flexion are likely a factor causing problems of posterior instability in current total knee arthroplasty. Thus, it is important to consider the magnitude of the loads at the knee in the treatment of patients that commonly perform deep flexion during activities of daily living.

    View details for Web of Science ID 000177191600034

    View details for PubMedID 12168682

  • Increased knee joint loads during walking are present in subjects with knee osteoarthritis OSTEOARTHRITIS AND CARTILAGE Baliunas, A. J., Hurwitz, D. E., Ryals, A. B., Karrar, A., CASE, J. P., Block, J. A., Andriacchi, T. P. 2002; 10 (7): 573-579

    Abstract

    This study tests the hypothesis that the peak external knee adduction moment during gait is increased in a group of ambulatory subjects with knee osteoarthritis (OA) of varying radiographic severity who are being managed with medical therapy. Tibiofemoral knee OA more commonly affects the medial compartment. The external knee adduction moment can be used to assess the load distribution between the medial and lateral compartments of the knee joint. Additionally, this study tests if changes in the knee angles, such as a reduced midstance knee flexion angle, or reduced sagittal plane moments previously identified by others as load reducing mechanisms are present in this OA group.Thirty-one subjects with radiographic evidence of knee OA and medial compartment cartilage damage were gait tested after a 2-week drug washout period. Thirty-one normal subjects (asymptomatic control subjects) with a comparable age, weight and height distribution were also tested. Significant differences in the sagittal plane knee motion and peak external moments between the normal and knee OA groups were identified using t tests.Subjects with knee OA walked with a greater than normal peak external knee adduction moment (P=0.003). The midstance knee flexion angle was not significantly different between the two groups (P=0.625) nor were the peak flexion and extension moments (P> 0.037).Load reducing mechanisms, such as a decreased midstance knee flexion angle, identified by others in subjects with endstage knee OA or reduced external flexion or extension moments were not present in this group of subjects with knee OA who were being managed by conservative treatment. The finding of a significantly greater than normal external knee adduction moment in the knee OA group lends support to the hypothesis that an increased knee adduction moment during gait is associated with knee OA.

    View details for DOI 10.1053/joca.2002.0797

    View details for Web of Science ID 000177625700010

    View details for PubMedID 12127838

  • Quantitative analysis of the relative effectiveness of 3 iliotibial band stretches ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION Fredericson, M., White, J. J., MacMahon, J. M., Andriacchi, T. P. 2002; 83 (5): 589-592

    Abstract

    To compare the relative effectiveness of 3 common standing stretches for the iliotibial band (ITB): arms at side (stretch A), arms extending overhead (stretch B), and arms reaching diagonally downward (stretch C).Each subject's biomechanics was captured as a 3-dimensional image by using a 4-camera gait acquisition system with a forceplate.University biomotion laboratory.Five male elite-level distance runners.All participants performed each of the 3 standing stretches for the ITB.For each stretch, change in ITB tissue length and the force generated within the stretched complex was measured. Data were then combined and analyzed by using kinetic values assessment.All 3 stretches created statistically significant changes in ITB length (P<.05), but stretch B, incorporating overhead arm extension, was consistently most effective both for average ITB length change and average adduction moments at the hip and knee.Adding an overhead arm extension to the most common standing ITB stretch may increase average ITB length change and average external adduction moments in elite-level distance runners.

    View details for DOI 10.1053/apmr.2002.31606

    View details for Web of Science ID 000175494000001

    View details for PubMedID 11994795

  • Failure and fatigue characteristics of adhesive athletic tape MEDICINE AND SCIENCE IN SPORTS AND EXERCISE Bragg, R. W., MacMahon, J. M., Overom, E. K., Yerby, S. A., Matheson, G. O., Carter, D. R., Andriacchi, T. P. 2002; 34 (3): 403-410

    Abstract

    Athletic tape has been commonly reported to lose much of its structural support after 20 min of exercise. Although many studies have addressed the functional performance characteristics of athletic tape, its mechanical properties are poorly understood. This study examines the failure and fatigue properties of several commonly used athletic tapes.A Web-based survey of professional sports trainers was used to select the following three tapes for the study: Zonas (Johnson & Johnson), Leukotape (Beiersdorf), and Jaylastic (Jaybird & Mais). Using a hydraulic material testing system (MTS), eight samples of each tape were compared in three different mechanical tests: load-to-failure, fatigue testing under load control, and fatigue testing under displacement control. Differences in tape microstructure were used to interpret the results of the mechanical tests.Significant differences (P < 0.001) in failure load, elongation at failure, and stiffness were found from failure tests. Significant differences were also found (P < 0.001) in fatigue behavior under both modes of control. As a representative example, in one normalized displacement control fatigue test after 20 min of cycling, 21% (Zonas), 29% (Leukotape), and 57% (Jaylastic) of the mechanical support was lost. After cycling, all tapes loaded to failure showed increased stiffness (P < 0.001), indicating significant energy absorption during cycling. Observed differences in the tapes' microstructure were qualitatively consistent with the measured differences in their mechanical properties.In understanding the shortcomings of currently available tapes, the results of these tests can now be used as benchmarks with which to compare and develop future tape designs. Ultimately, these improved tapes should reduce ankle injuries among athletes.

    View details for Web of Science ID 000174268300004

    View details for PubMedID 11880802

  • The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain JOURNAL OF ORTHOPAEDIC RESEARCH Hurwitz, D. E., Ryals, A. B., CASE, J. P., Block, J. A., Andriacchi, T. P. 2002; 20 (1): 101-107

    Abstract

    This study tested whether the peak external knee adduction moments during walking in subjects with knee osteoarthritis (OA) were correlated with the mechanical axis of the leg, radiographic measures of OA severity, toe out angle or clinical assessments of pain, stiffness or function. Gait analysis was performed on 62 subjects with knee OA and 49 asymptomatic control subjects (normal subjects). The subjects with OA walked with a greater than normal peak adduction moment during early stance (p = 0.027). In the OA group, the mechanical axis was the best single predictor of the peak adduction moment during both early and late stance (R = 0.74, p < 0.001). The radiographic measures of OA severity in the medial compartment were also predictive of both peak adduction moments (R = 0.43 to 0.48, p < 0.001) along with the sum of the WOMAC subscales (R = -0.33 to -0.31, p < 0.017). The toe out angle was predictive of the peak adduction moment only during late stance (R = -0.45, p < 0.001). Once mechanical axis was accounted for, other factors only increased the ability to predict the peak knee adduction moments by 10 18%. While the mechanical axis was indicative of the peak adduction moments, it only accounted for about 50% of its variation, emphasizing the need for a dynamic evaluation of the knee joint loading environment. Understanding which clinical measures of OA are most closely associated with the dynamic knee joint loads may ultimately result in a better understanding of the disease process and the development of therapeutic interventions.

    View details for Web of Science ID 000173353800014

    View details for PubMedID 11853076

  • Linking the biology of osteoarthritis to locomotion mechanics MANY FACES OF OSTEOARTHRITIS Thonar, E. J., Hurwitz, D. E., Andriacchi, T. P., Lenz, M. E., Sharma, L. 2002: 453-460
  • Correcting for deformation in skin-based marker systems JOURNAL OF BIOMECHANICS Alexander, E. J., Andriacchi, T. P. 2001; 34 (3): 355-361

    Abstract

    A new technique is described that reduces error due to skin movement artifact in the opto-electronic measurement of in vivo skeletal motion. This work builds on a previously described point cluster technique marker set and estimation algorithm by extending the transformation equations to the general deformation case using a set of activity-dependent deformation models. Skin deformation during activities of daily living are modeled as consisting of a functional form defined over the observation interval (the deformation model) plus additive noise (modeling error). The method is described as an interval deformation technique. The method was tested using simulation trials with systematic and random components of deformation error introduced into marker position vectors. The technique was found to substantially outperform methods that require rigid-body assumptions. The method was tested in vivo on a patient fitted with an external fixation device (Ilizarov). Simultaneous measurements from markers placed on the Ilizarov device (fixed to bone) were compared to measurements derived from skin-based markers. The interval deformation technique reduced the errors in limb segment pose estimate by 33 and 25% compared to the classic rigid-body technique for position and orientation, respectively. This newly developed method has demonstrated that by accounting for the changing shape of the limb segment, a substantial improvement in the estimates of in vivo skeletal movement can be achieved.

    View details for Web of Science ID 000167482500009

    View details for PubMedID 11182127

  • Dynamic function after anterior cruciate ligament reconstruction with autologous patellar tendon AMERICAN JOURNAL OF SPORTS MEDICINE Bush-Joseph, C. A., Hurwitz, D. E., Patel, R. R., Bahrani, Y., Garretson, R., Bach, B. R., Andriacchi, T. P. 2001; 29 (1): 36-41

    Abstract

    The purpose of this study was to dynamically assess the functional outcome of patients who had undergone successful anterior cruciate ligament reconstruction using an autologous patellar tendon technique and to determine whether their dynamic knee function was related to quadriceps and hamstring muscle strength. The knee kinematics and kinetics of 22 subjects who had undergone anterior cruciate ligament reconstruction (mean age, 27 +/- 11 years) and of 22 age- and sex-matched healthy control subjects were determined during various dynamic activities using a computerized motion analysis and force plate system. The differences in the sagittal plane angles and external moments between the two groups during light (walking), moderate (climbing and descending stairs), and higher-demand (jogging, jog and cut, jog and stop) activities were related to isokinetic strength measurements. Although patients who are asymptomatic and functioning well after anterior cruciate ligament reconstruction can perform normally in light activities, higher-demand activities reveal persistent functional adaptations that require further study.

    View details for Web of Science ID 000166779200008

    View details for PubMedID 11206254

  • Functional gait adaptations in patients with painful hip REVUE DE CHIRURGIE ORTHOPEDIQUE ET REPARATRICE DE L APPAREIL MOTEUR Hulet, C., Hurwitz, D. E., Andriacchi, T. P., Galante, J. O., Vielpeau, C. 2000; 86 (6): 581-589

    Abstract

    This prospective study was conducted to analyze the mechanisms of gait compensation in patients with painful hip and to search for correlations with preoperative clinical and radiographic findings.Optoelectronic and multicomponent force-plate datas were used to calculate joint motion, moments and intersegmental forces for 26 patients with unilateral hip pain and 20 normal age and sex-matched patients. Height was similar in the two groups but mean weight in the study group (83 kg) was greater than in the controls (68 kg). The preoperative Harris score was 53 in the study group and 16 patients had a permanent flexion contracture of the knee (mean 15 degrees, range 5-30 degrees). Radiographically, there were 22 cases of osteo-arthritis hip disease and 4 cases of necrosis.Gait analysis showed a significant 0.66 +/- 0.06 m (12 p. 100) reduction in step length. Patients who had severe hip pain walked with a decreased dynamic range of motion (18 +/- 5 degrees, p<0.0001) with a curve reversal as they extended the hip. They also reduced dynamic range of motion of the knee and ankle. Patients who presented a reversal in their dynamic hip range of motion had a greater passive flexion contracture and a greater loss in range of motion during gait than those with a smooth regular pattern (p<0.0001). Patients with hip pain walked with significantly decreased external extension, adduction, and internal and external rotation moments (p<0.0001). They also unloaded the ipsilateral knee and ankle. The decreased hip extension moment was significantly correlated with an increased level of pain (p<0.0001). There was no correlation with radiological findings.Reversal of dynamic hip range of motion was interpreted as a mechanism to increase effective hip extension during stance phase through increased anterior pelvic tilt and lumbar lordosis.Patients with painful hip walked with a manner that was asymmetric. These gait modifications were related to hip limitation in passive motion and pain. Patients with flexion contracture adopted a compensatory gait mechanism. This study confirms relation between hip pain and forces across the hip joint.

    View details for Web of Science ID 000165281500005

    View details for PubMedID 11060432

  • Knee pain and joint loading in subjects with osteoarthritis of the knee JOURNAL OF ORTHOPAEDIC RESEARCH Hurwitz, D. E., Ryals, A. R., Block, J. A., Sharma, L., Schnitzer, T. J., Andriacchi, T. P. 2000; 18 (4): 572-579

    Abstract

    Although treatments for osteoarthritis of the knee are often directed at relieving pain, pain may cause patients to alter how they perform activities to decrease the loads on the joints. The knee-adduction moment is a major determinant of the load distribution between the medial and lateral plateaus. Therefore, the interrelationship between pain and the external knee-adduction moment during walking may be especially important for understanding mechanical factors related to the progression of medial tibiofemoral osteoarthritis. Fifty-three subjects with symptomatic radiographic evidence of osteoarthritis of the knee were studied. These subjects were a subset of those enrolled in a double-blind study in which gait analysis and radiographic and clinical evaluations were performed after a 2-week washout of anti-inflammatory and analgesic treatment. The subjects then took a nonsteroidal anti-inflammatory drug, acetaminophen, or placebo for 2 weeks, and the gait and clinical evaluations were repeated. The change in the peak external adduction moment between the two evaluations was inversely correlated with the change in pain (R = 0.48, p < 0.001) and was significantly different between those whose pain increased (n = 7), decreased (n = 18), or remained unchanged (n = 28) (p = 0.009). Those with increased pain had a significant decrease in the peak external adduction (p = 0.005) and flexion moments (p = 0.023). In contrast, the subjects with decreased pain tended to have an increase in the peak external adduction moment (p = 0.095) and had a significant increase in the peak external extension moment (p = 0.017). The subjects whose pain was unchanged had no significant change in the peak external adduction (p = 0.757), flexion (p = 0.234), or extension (p = 0.465) moments. Thus, decreases in pain among patients with medial tibiofemoral osteoarthritis were related to increased loading of the degenerative portion of the joints. Additional long-term prospective studies are needed to determine whether increased loading during walking actually results in accelerated progression of the disease.

    View details for Web of Science ID 000089921300008

    View details for PubMedID 11052493

  • Abnormalities in muscle function during gait in relation to the level of lumbar disc herniation SPINE Morag, E., Hurwitz, D. E., Andriacchi, T. P., Hickey, M., Andersson, G. B. 2000; 25 (7): 829-833

    Abstract

    A comparison between gait in patients undergoing surgery for L4 and L5 lumbar disc herniations and that in an age- and weight-matched control group.To study whether changes in the moments produced at the ankle and knee joints during walking reflect the neurologic level of a herniated nucleus pulposus.Lumbar herniated discs often cause muscle weakness, reduced motor function, and change in walking capacity. The specific effects of a disc herniation on muscle function during gait is poorly documented.Conventional physical examination and kinetic analysis of gait were performed on 16 patients who subsequently underwent surgery for herniated discs (eight with L4-L5 and eight with L5-S1 disc herniations) and 16 healthy control subjects. The three components of the external moment at the ankle and knee were computed. The peak magnitudes of specific components of the external moments were compared with those of the control group.Reduced external ankle plantar flexion moment, indicating a decreased function of the ankle dorsiflexors, was found in patients with herniated nucleus pulposus of both L4-L5 and L5-S1. Reduced external ankle dorsiflexion moment, indicating a decreased function of the ankle plantar flexors, was found only in patients with a lesion to the L5-S1 disc, but not in those with herniations at L4-L5.Preoperative gait analysis identified functional deficits of the muscles about the ankle and foot that relate to the level of the herniation. Kinetic measurements can assist in understanding the functional limitations associated with specific levels of a herniation.

    View details for Web of Science ID 000086483100013

    View details for PubMedID 10751294

  • Methodology for long-term wear testing of total knee replacements CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Walker, P. S., Blunn, G. W., Perry, J. P., Bell, C. J., Sathasivam, S., Andriacchi, T. P., Paul, J. P., Haider, H., Campbell, P. A. 2000: 290-301

    Abstract

    This article begins to address the validation requirements of wear testing on total knee replacements in a knee simulator. The knee simulator has four stations. The axial force is variable but reaches a maximum of 2.3 kN. Physiologic anteroposterior shear force and rotational torques are supplied to the knee. The forces and displacements are timed to coincide with those of a typical gait cycle. Kinematics of the simulator are dependent on the type of knee being tested. Tests of designs with well known clinical histories were done to 10 million cycles. The relative amounts and types of wear shown by the designs were similar to that found in their clinical histories. Wear tracks on more conforming designs were larger, and the penetration into the plastic appeared to be less. This did not necessarily mean that wear, as measured by loss of material, was reduced on conforming designs. Delamination of the plastic was achieved only after aging the tibial components. Wear particles isolated from the lubricating fluid were similar in size and shape to those isolated from in vivo specimens. However, the relative amounts of wear particle shapes were different depending on the design. At the start of the tests, all of the flexibly mounted tibial components showed more motion than after 5 million cycles, indicating that the surface of the plastic became more conforming. This study showed that knee wear similar to wear observed in vivo can be reproduced in the laboratory. The parameters and methods elucidated in this introductory study should form the basis for use in preclinical wear tests of total knee replacements.

    View details for Web of Science ID 000085864200032

    View details for PubMedID 10738439

  • Methods for evaluating the progression of osteoarthritis JOURNAL OF REHABILITATION RESEARCH AND DEVELOPMENT Andriacchi, T. P., Lang, P. L., Alexander, E. J., Hurwitz, D. E. 2000; 37 (2): 163-170

    Abstract

    This article discusses methods for evaluating the progression of osteoarthritis through dynamic functional imaging as opposed to current static techniques. Comparison is made between static and dynamic methods of evaluating knee alignment. The correlation between dynamic knee moments during gait and bone mineral content is discussed. Knee loading is considered in terms of high tibial osteotomy, knee braces, pain, and non-steroidal anti-inflammatory drugs. New image-processing techniques for quantitating cartilage loss are described, and computational methods for generating true three-dimensional (3-D) maps of cartilage thickness are developed. Finally, new approaches to cross-correlate magnetic resonance images with kinematic measurements are described. These new techniques promise to become powerful diagnostic tools to detect and characterize pathological load distributions across articular cartilage.

    View details for Web of Science ID 000165733400009

    View details for PubMedID 10850822

  • Characterization of gait parameters in patients with Charcot-Marie-Tooth disease NEUROLOGY INDIA Kuruvilla, A., Costa, J. L., WRIGHT, R. B., Yoder, D. M., Andriacchi, T. P. 2000; 48 (1): 49-55

    Abstract

    The gait of five patients with Charcot-Marie-Tooth(CMT) disease was analyzed using light-emitting diodes and a force plate. The flexion-extension motions of the hips, knees, and ankles, as well as their moments (vector sums of forces acting at the joints) in the flexion-extension and abduction-adduction planes, were quantified. The gait of the CMT patients showed abnormalities consistent with both distal weakness (ankle dorsi- and plantar-flexors) and weakness of the hip abductor muscles. The latter weakness appeared to produce asymmetric hip moments and truncal instability in the mediolateral plane during ambulation. However, the extent to which the gait was abnormal appeared not to be exclusively related to the severity of the sensorimotor conduction deficits in the peripheral nerves. In the four patients for whom nerve conduction velocity studies were available, decrease in the lower-extremity distal conduction velocities and evoked motor amplitude potentials did not correlate with the severity and extent of the gait abnormalities.

    View details for Web of Science ID 000086991700010

    View details for PubMedID 10751814

  • Functional adaptations in patients with ACL-deficient knees PROPRIOCEPTION AND NEUROMUSCULAR CONTROL IN JOINT STABILITY Andriacchi, T. P., Hurwitz, D. E., Bush-Joseph, C. A., Bach, B. R. 2000: 181-188
  • Effect of knee pain on joint loading in patients with osteoarthritis. Current opinion in rheumatology Hurwitz, D. E., Sharma, L., Andriacchi, T. P. 1999; 11 (5): 422-426

    Abstract

    Treatment of patients with osteoarthritis is often directed at relieving pain and restoring function. Pain, however, may serve as a protective mechanism in that patients may decrease their levels of activity or alter the manner in which they perform activities in response to pain. Pain reduction may result in increased loads on the joints during dynamic activities, which may result in more rapid disease progression. Therefore, treatment methods that relieve pain but result in a loss of the protective mechanisms associated with pain may not be beneficial in the long term. This mechanism of decreased pain associated with an overuse of the degenerated joint has been referred to as an "analgesic arthropathy." This article discusses common treatments or interventions used for patients with knee osteoarthritis and their potential effects on pain levels and loads at the knee joint during walking. Understanding the relationship between treatment methods, pain, and the knee joint loads during walking is important because walking is the most frequently performed activity, and the cyclic loads at the knee joint during walking are high.

    View details for PubMedID 10503665

  • Study on effect of graded facetectomy on change in lumbar motion segment torsional flexibility using three-dimensional continuum contact representation for facet joints JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Natarajan, R. N., Andersson, G. B., Patwardhan, A. G., Andriacchi, T. P. 1999; 121 (2): 215-221

    Abstract

    Facet joints provide rigidity to the lumbar motion segment and thus protect the disk, particularly against torsional injury. A surgical procedure that fully or partially removes the facet joints (facetectomy) will decrease the mechanical stiffness of the motion segment, and potentially place the disk at risk of injury. Analytical models can be used to understand the effect of facet joints on motion segment stability. Using a facet joint model that represents the contact area as contact between two surfaces rather than as point contact, it was concluded that a substantial sudden change in rotational motion, due to applied torsion moment, was observed after 75 percent of any one of the facet joints was removed. Applied torsional moment loading produced coupled extension motion in the intact motion segment. This coupled motion also experienced a large change following complete unilateral facetectomy. Clinically, the present study showed that surgical intervention in the form of unilateral or bilateral total facetectomy might require fusion to reduce the primary torsion motion.

    View details for Web of Science ID 000079930400011

    View details for PubMedID 10211456

  • Vivo motion analysis: Applied to a study of knee kinematics JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME Andriacchi, T. P., Alexander, E. J., Toney, M. K., Dyrby, C. 1998; 120 (6): 743-749

    Abstract

    A new method for deriving limb segment motion from markers placed on the skin is described. The method provides a basis for determining the artifact associated with nonrigid body movement of points placed on the skin. The method is based on a cluster of points uniformly distributed on the limb segment. Each point is assigned an arbitrary mass. The center of mass and the inertia tensor of this cluster of points are calculated. The eigenvalues and eigenvectors of the inertia tensor are used to define a coordinate system in the cluster as well as to provide a basis for evaluating non-rigid body movement. The eigenvalues of the inertia tensor remain invariant if the segment is behaving as a rigid body, thereby providing a basis for determining variations for nonrigid body movement. The method was tested in a simulation model where systematic and random errors were introduced into a fixed cluster of points. The simulation demonstrated that the error due to nonrigid body movement could be substantially reduced. The method was also evaluated in a group of ten normal subjects during walking. The results for knee rotation and translation obtained from the point cluster method compared favorably to results previously obtained from normal subjects with intra-cortical pins placed into the femur and tibia. The resulting methodology described in this paper provides a unique approach to the measurement of in vivo motion using skin-based marker systems.

    View details for Web of Science ID 000077716900009

    View details for PubMedID 10412458

  • Hip motion and moments during gait relate directly to proximal femoral bone mineral density in patients with hip osteoarthritis JOURNAL OF BIOMECHANICS Hurwitz, D. E., Foucher, K. C., Sumner, D. R., Andriacchi, T. P., Rosenberg, A. G., Galante, J. O. 1998; 31 (10): 919-925

    Abstract

    The present study examined the loads at the hip joint during gait and the bone mineral density of the proximal femur in 25 patients with end-stage hip osteoarthritis. Dual energy X-ray absorptiometry was used to determine the bone mineral density of the greater trochanter, femoral neck and Ward's triangle of the osteoarthritic group. The bone mineral density was normalized for the patient's age, gender, weight and ethnic origin (Z score). Gait analysis was used to determine the external hip joint moments and motion during walking for the osteoarthritic group and a control group of 21 normal subjects. The gait parameters of the osteoarthritic group which were significantly diminished compared to the normal group (p < 0.001) accounted for as much as 42% (p < 0.001) of the variation in the normalized bone mineral density. Specifically, the dynamic sagittal plane hip motion during gait (maximum flexion minus maximum extension) and peak external rotation and adduction moments were significantly correlated with greater trochanter (R = 0.429-0.648, p = 0.032-0.0001) and Ward's triangle (R = 0.418-0.532, p = 0.038-0.006) normalized bone mineral density while the adduction moment was also significantly correlated with the femoral neck normalized bone mineral density (R = 0.5394, p = 0.005). The normalized bone mineral density of the femoral neck and Ward's triangle was elevated while that of the greater trochanter was decreased as compared to normal reference values. The significant correlation between the hip joint moments during gait and femoral bone mineral density indicate that hip joint loads need to be included when explaining local variation in bone mineral density in hip osteoarthritis.

    View details for Web of Science ID 000077061600007

    View details for PubMedID 9840757

  • Knee adduction moment, serum hyaluronan level, and disease severity in medial tibiofemoral osteoarthritis ARTHRITIS AND RHEUMATISM Sharma, L., Hurwitz, D. E., Thonar, E. J., Sum, J. A., Lenz, M. E., Dunlop, D. D., Schnitzer, T. J., Kirwan-Mellis, G., Andriacchi, T. P. 1998; 41 (7): 1233-1240

    Abstract

    The adduction moment at the knee during gait is the primary determinant of medial-to-lateral load distribution. If the adduction moment contributes to progression of osteoarthritis (OA), then patients with advanced medial tibiofemoral OA should have higher adduction moments. The present study was undertaken to investigate the hypothesis that the adduction moment normalized for weight and height is associated with medial tibiofemoral OA disease severity after controlling for age, sex, and pain level, and to examine the correlation of serum hyaluronan (HA) level with disease severity and with the adduction moment in a subset of patients.Fifty-four patients with medial tibiofemoral OA underwent gait analysis and radiographic evaluation. Disease severity was assessed using the Kellgren-Lawrence (K-L) grade and medial joint space width. In a subset of 23 patients with available sera, HA was quantified by sandwich enzyme-linked immunosorbent assay. Pearson correlations, a random effects model, and multivariate regression models were used.The adduction moment correlated with the K-L grade in the left and right knees (r = 0.68 and r = 0.60, respectively), and with joint space width in the left and right knees (r = -0.45 and r = -0.47, respectively). The relationship persisted after controlling for age, sex, and severity of pain. The partial correlation between K-L grade and adduction moment was 0.71 in the left knees and 0.61 in the right knees. For every 1.0-unit increase in adduction moment, there was a 0.63-mm decrease in joint space width. In the subset of patients in whom serum HA levels were measured, HA levels correlated with medial joint space width (r = -0.55), but not with the adduction moment.There is a significant relationship between the adduction moment and OA disease severity. Serum HA levels correlate with joint space width but not with the adduction moment. Longitudinal studies will be necessary to determine the contribution of the adduction moment, and its contribution in conjunction with metabolic markers, to progression of medial tibiofemoral OA.

    View details for Web of Science ID 000074585400013

    View details for PubMedID 9663481

  • Dynamic knee loads during gait predict proximal tibial bone distribution JOURNAL OF BIOMECHANICS Hurwitz, D. E., Sumner, D. R., Andriacchi, T. P., Sugar, D. A. 1998; 31 (5): 423-430

    Abstract

    This study tested the validity of the prediction of dynamic knee loads based on gait measurements. The relationship between the predicted loads at the knee and the distribution of bone between the medial and lateral sides of the tibia was examined. The motion and external forces and moments at the knee were measured during gait and a statically determinate muscle model was used to predict the corresponding forces on the medial and lateral tibial plateaus. In particular, the relationship between the knee adduction moment during gait and the ratio or distribution of medial to lateral tibial bone mineral content was studied. Bone mineral content was measured with dual energy X-ray absorptiometry in four regions, two proximal regions 20 mm in height, one medial and one lateral and two distal regions 20 mm in height, one medial and one lateral. The best single predictor of the medial lateral ratio of proximal bone mineral content (bone distribution) was the adduction moment (R2=0.31, p=0.003). Adding weight (negative coefficient. p=0.0004) and the ratio of the average predicted peak force on the medial plateau to the predicted peak force on the lateral plateau (positive coefficient, p=0.0033) to the regression model significantly increased the ability to predict the proximal medial lateral bone distribution (R2=0.72, p=0.0001). Distally neither the subject characteristics nor the gait moments and predicted forces were significant predictors of the bone distribution. The lack of a correlation distally may be reflective of the forces being more evenly distributed further from the tibial plateau. While it has long been suggested that the adduction moment is the primary determinate of the distribution of load between the medial and lateral plateaus, this is the first evidence of its relationship to the underlying bone distribution.

    View details for Web of Science ID 000075497300003

    View details for PubMedID 9727339

  • Functional gait adaptations in patients with anterior cruciate ligament deficiency over time CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Wexler, G., Hurwitz, D. E., Bush-Joseph, C. A., Andriacchi, T. P., Bach, B. R. 1998: 166-175

    Abstract

    Functional adaptations in knee kinematics and kinetics during level walking in 30 patients with unilateral anterior cruciate ligament deficiency and 30 healthy control subjects were studied. To examine the impact of time after injury on the functional adaptations, patients were placed into three time interval groups: early, intermediate, and chronic. The patients with anterior cruciate ligament deficiency had significantly decreased external knee flexion moments (balanced by net quadriceps contraction) and significantly increased external knee extension moments (balanced by net knee flexors contraction) as compared with the control subjects. As time after the injury increased, changes in the sagittal plane knee moments were more pronounced. A significant linear relationship (positive correlation) was found between the midstance knee flexion moment and the corresponding knee flexion angle. The patients with anterior cruciate deficiency had a greater knee flexion angle when generating a comparable midstance knee flexion moment as compared to the control subjects. The identification of gait adaptations over time provides additional information on the natural history of anterior cruciate ligament deficiency and may have implications regarding conservative rehabilitation, evaluation of outcomes, progression of meniscal injury, and the development of degenerative arthritis of the knee.

    View details for Web of Science ID 000072887000026

    View details for PubMedID 9553549

  • Practical and theoretical considerations in the application in the development of clinical gait analysis BIO-MEDICAL MATERIALS AND ENGINEERING Andriacchi, T. P. 1998; 8 (3-4): 137-143

    View details for Web of Science ID 000078402500004

    View details for PubMedID 10065880

  • A striated pattern of wear in ultrahigh-molecular-weight polyethylene components of Miller-Galante total knee arthroplasty JOURNAL OF ARTHROPLASTY Wimmer, M. A., Andriacchi, T. P., Natarajan, R. N., Loos, J., Karlhuber, M., Petermann, J., Schneider, E., Rosenberg, A. G. 1998; 13 (1): 8-16

    Abstract

    Wear of the polyethylene tibial components is a potential cause of failure in total knee arthroplasty. In addition to pitting, burnishing, and scratching, subtle striations on the bearing portion of the tibial surface have been observed in components retrieved relatively early after implantation. The striated pattern most typically occurred in areas centrally located within the articulating surface. The striations were anteroposterior directed and were identified as local cold flow at the surface. There was a strong correlation between the medial and lateral striated areas, suggesting that these patterns are related to cyclic rolling of the knee. The general characteristics and alignment of the striations could be attributed to the compressive and tractive forces occurring during femoral rollback. For the clinician, these results suggest that kinematics, as well as contact stress, should be considered when evaluating wear of polyethylene components.

    View details for Web of Science ID 000072498600002

    View details for PubMedID 9493532

  • Joint loading with valgus bracing in patients with varus gonarthrosis CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Lindenfeld, T. N., Hewett, T. E., Andriacchi, T. P. 1997: 290-297

    Abstract

    The purpose of this study was to determine whether a brace designed to unload varus degenerative knees actually alters medial compartment loads by decreasing the adduction moment. Eleven patients who had arthrosis confined to the medial compartment were fitted with a valgus brace and tested before and after brace wear with pain and function scoring instruments and by automated gait analysis. The biomechanical data from these patients were compared with those from 11 healthy control subjects. Scores from an analog pain scale decreased 48% with brace wear, and function with activities of daily living increased 79%. Mean adduction moment without the brace measured 4.0 +/- 0.8% body weight times height versus 3.6 +/- 0.8% body weight times height when wearing the brace (10% decrease). The mean adduction moment for control subjects was 3.5 +/- 0.6% body weight times height. Thus, the mean adduction moment decreased from approximately one standard deviation from the normal mean to a value that is similar to the control value. Nine of 11 patients had a decrease in the adduction moment with the brace, five of 11 patients had a reduction higher than 10%, and decreases in this moment were as high as 32%. This study shows that pain, function, and biomechanical knee loading can be altered by a brace designed to unload the medial compartment of the knee.

    View details for Web of Science ID A1997YF26500029

    View details for PubMedID 9372780

  • Gait biomechanics and total knee arthroplasty. The American journal of knee surgery Andriacchi, T. P., Hurwitz, D. E. 1997; 10 (4): 255-260

    View details for PubMedID 9421602

  • Gait compensations in patients with osteoarthritis of the hip and their relationship to pain and passive hip motion JOURNAL OF ORTHOPAEDIC RESEARCH Hurwitz, D. E., Hulet, C. H., Andriacchi, T. P., Rosenberg, A. G. 1997; 15 (4): 629-635

    Abstract

    This study related mechanisms of gait compensations to the level of pain and to limitations in passive motion in patients with osteoarthritis of the hip. Joint motion, moments, and intersegmental forces were calculated for 19 patients with unilateral osteoarthritis of the hip (12 men and seven women) and for a group of normal subjects (12 men and seven women) with a similar age distribution. The patients who had osteoarthritis walked with a decreased dynamic range of motion (17 +/- 4 degrees) of the hip and with a hesitation or reversal in the direction of the sagittal plane motion as they extended the hip. The patients with a hesitation or reversal in motion had a greater loss in the range of motion of the hip during gait (p < 0.004) and a greater passive flexion contracture (p < 0.022) than those with a smooth pattern of hip motion. This alteration in the pattern of motion was interpreted as a mechanism to increase effective extension of the hip during stance through increased anterior pelvic tilt and lumbar lordosis. The patients who had osteoarthritis of the hip walked with significantly decreased external extension, adduction, and internal and external rotation moments (p < 0.008). The decreased extension moment was significantly correlated with an increased level of pain (R = 0.78; p < 0.001). This finding suggests that decreasing muscle forces (hip flexors) may be one mechanism used to adapt to pain.

    View details for Web of Science ID A1997YA23000020

    View details for PubMedID 9379275

  • Patellofemoral design influences function following total knee arthroplasty JOURNAL OF ARTHROPLASTY Andriacchi, T. P., Yoder, D., Conley, A., Rosenberg, A., Sum, J., Galante, J. O. 1997; 12 (3): 243-249

    Abstract

    The functional influence of patellofemoral design was evaluated by testing two cohorts of patients with total knee arthroplasty while walking, climbing stairs, and rising from a chair. The two cohorts received one of two different designs of total knee arthroplasty. The designs differed primarily in the curvature of the femoral trochlea. These differences in curvature have been shown in in vitro studies to influence the tracking of the patella. One design had a smaller radius on the patellar flange, which caused the patella to articulate more anteriorly and distally than the second design, which had a larger radius in this region. The second design more closely replicated the curvature of the femoral trochlear anatomy. There was a significant functional difference during stairclimbing between the patient groups, whereas there was no difference during walking or chair rising. The group with the design that had nonanatomic tracking of the patella had a higher than normal moment tending to flex the knee (net quadriceps moment) during late stance phase. The increased net quadriceps moment during late stance was concurrent with an increased knee flexion. The abnormal function occurred when the patellar was tracking over the nonanatomic portion of the trochlea. Patients in the group with the anatomic trochlea did not have abnormal function. These results suggest a relationship between a nonanatomic trochlea and abnormal function during stair-climbing.

    View details for Web of Science ID A1997WU68800002

    View details for PubMedID 9113537

  • Tractive forces during rolling motion of the knee: Implications for wear in total knee replacement JOURNAL OF BIOMECHANICS Wimmer, M. A., Andriacchi, T. P. 1997; 30 (2): 131-137

    Abstract

    Wear at the polyethylene tibial plateau in total knee arthroplasty (TKR) is one of the primary concerns with these devices. The artificial bearing of a TKR has to sustain large forces while allowing the mobility for normal motion, typically, rolling, gliding and rotation. The tractive forces during the rolling motion at the knee joint were analyzed to determine which factors cause these forces to increase in TKR. The implications of these tractive forces to polyethylene wear were considered. Traction forces were calculated using a model of the knee to evaluate the effect of variations in the coefficient of friction, gait characteristics, antagonistic muscle contraction and patellofemoral mechanics. The model was limited to the sagittal plane motion of the femur on the tibia. The input for the model was the shape of the articulating surface, coefficient of friction, contact path, muscle anatomy and gait kinetics common to patients with a total knee replacement. The generation of tractive forces on the tibial polyethylene plateau was highly dependent on the static and dynamic coefficient of friction between the femur and the tibia. A peak tractive force of approximately 0.4 body weight was calculated with a peak normal force of 3.3 body weight. Tractive rolling occurred during most of stance phase when the static coefficient was 0.2. Alterations in gait patterns had a substantial effect on the generation of tractive forces at the knee joint. When an abnormal gait pattern (often seen following TKR) was input to the model the posteriorly directed tractive force on the tibial surface was reduced. It was also found that variations in muscle contractions associated with antagonistic muscle activity as well as the angle of pull of the patellar tendon affected the magnitude of tractive forces. The results of the study suggest that there are feasible conditions following total knee replacement which can lead to tractive forces during rolling motion at the tibiofemoral articulation that should be considered in the analysis of factors leading to polyethylene damage in total knee replacement.

    View details for Web of Science ID A1997WC30400005

    View details for PubMedID 9001933

  • Functional adaptations in patients with ACL-deficient knees. Exercise and sport sciences reviews Hurwitz, D. E., Andriacchi, T. P., Bush-Joseph, C. A., Bach, B. R. 1997; 25: 1-20

    View details for PubMedID 9213086

  • Altered load history affects periprosthetic bone loss following cementless total hip arthroplasty JOURNAL OF ORTHOPAEDIC RESEARCH Bryan, J. M., Sumner, D. R., Hurwitz, D. E., TOMPKINS, G. S., Andriacchi, T. P., Galante, J. O. 1996; 14 (5): 762-768

    Abstract

    Dual energy x-ray absorptiometry was used to measure periprosthetic, distal femoral, and proximal tibial bone mass in the affected and contralateral limbs of eight patients 10 years after unilateral total hip arthroplasty with a cementless, porous-coated titanium alloy femoral stem. Gait analyses to assess the presence of asymmetries in loading of the lower extremities were also performed 10 years postoperatively. The patients had excellent clinical results and no other significant lower extremity pathology. On the basis of comparison of the affected and unaffected proximal femora, bone loss adjacent to the proximal medial aspect of the femoral stem was determined to be 34% (p < 0.001). However, the patients also had 16% less bone in the ipsilateral proximal tibia (p = 0.003) and 15% less bone in the ipsilateral femur 3 cm distal to the prosthesis (p = 0.007) compared with the contralateral limb. When normalized to the asymmetry in tibial bone mineral content, the estimated proximal medial periprosthetic bone loss was still statistically significant, but the magnitude was reduced from 34 to 17% (p = 0.009). The gait analyses indicated that several measures that influence the loads at the hip and knee joints were reduced in the involved limb compared with the contralateral limb. Furthermore, the bilateral difference in the vertical component of the external force acting on the proximal tibia was correlated with the bilateral difference in tibial bone mineral content (r = 0.80, p = 0.02). These data suggest that two mechanical factors, the local stress-shielding effect of the prosthesis and the global effect of decreased loading of the limb, can both make significant contributions to periprosthetic bone loss. It is apparent that the magnitude of the periprosthetic bone loss related to stress-shielding has been overestimated by as much as 50% in retrospective studies.

    View details for Web of Science ID A1996VP97200012

    View details for PubMedID 8893770

  • Adaptation to differential loading: Comparison of growth-related changes in cross-sectional properties of the human femur and humerus BONE Sumner, D. R., Andriacchi, T. P. 1996; 19 (2): 121-126

    Abstract

    Changes in long bone cross-sectional geometry during growth can be influenced by biological and mechanical factors. Here, we assess relationships between cross-sectional geometric properties and length of the human humerus and femur during postnatal growth to test the hypothesis that loading history plays an important role in the development of adult bone morphology. A skeletal sample including 83 paired humeri and femora from individuals between birth and age 30 was examined. Midshaft cross-sectional geometric properties were determined based on computed tomographic scans and the two bones were compared by examining growth trajectories and scaling relationships between the cross-sectional properties and bone length. The growth trajectories for both bones were similar in many respects and showed that increase in length ceased by age 20, whereas increase in cross-sectional properties continued into the third decade of life. When compared to bone length, the cross-sectional geometric properties of the femur and humerus were similar early in postnatal life, but increased at a greater rate in the femur particularly during the first decade of life, leading to divergent adult morphologies. A beam model was developed to predict maximum midshaft strains in each bone as a function of age. The moment acting on the femur was estimated from an analysis of gait in children and the moment acting on the humerus was chosen so that the magnitude of the maximum midshaft strains in the two bones was equivalent in adulthood. With this model, the maximum midshaft strains for the femur were predicted to be higher than for the humerus during the first decade of life. These data support the concept that load history plays an important role in accretion of bone mass during postnatal growth.

    View details for Web of Science ID A1996VB74000007

    View details for PubMedID 8853855

  • Functional analysis of cemented medial unicompartmental knee arthroplasty JOURNAL OF ARTHROPLASTY Chassin, E. P., MIKOSZ, R. P., Andriacchi, T. P., Rosenberg, A. G. 1996; 11 (5): 553-559

    Abstract

    Gait analysis was used to study patients who underwent cemented medial unicompartmental knee arthroplasty (UKA) for medial compartment degenerative knee disease. All had excellent clinical function of the operated knee, with minimal involvement of other joints. Ten patients met the inclusion criteria for this study. Gait findings from this study group, as well as those from a similar cohort of patients who had undergone total knee arthroplasty (TKA), were compared with those for a group of normal patients. A greater percentage of patients (7 of 10) following UKA maintained the normal biphasic flexion/extension moment pattern about the knee or demonstrated a quadriceps overuse pattern, when compared with similar groups following TKA. In addition, the adduction moment in patients following UKA was significantly larger than in patients following TKA. The postoperative limb alignment correlated with the peak adduction moment recorded during the patient's gait analysis. The postoperative alignment may explain the differences in the adduction moment between the UKA and TKA patients, as there tended to be residual varus in the UKA population. The results of this study imply that preservation of the anterior cruciate ligament during UKA allows patients to maintain normal quadriceps mechanics, and that residual varus alignment subjects a medial UKA to higher loads.

    View details for Web of Science ID A1996VF21000011

    View details for PubMedID 8872575

  • Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: A critical analysis of the reliability of gait analysis data JOURNAL OF ORTHOPAEDIC RESEARCH Andrews, M., Noyes, F. R., Hewett, T. E., Andriacchi, T. P. 1996; 14 (2): 289-295

    Abstract

    Anatomic and mechanical factors that affect loading in the knee joint can contribute to pathologic changes seen at the knee in degenerative joint disease and should be considered in treatment planning. The objectives of this study were to quantify the relationships between the alignment of the bones of the lower extremity, foot progression angle, and knee adduction moment, and to determine the reliability of our gait measurements. Gait analysis and complete radiographic evaluation of the lower extremity were performed on 11 healthy subjects. The gait measurements were recorded with an optoelectronic digitizer and a multi-component force plate. The subjects who had radiographic measurements indicative of varus alignment of the lower extremity had statistically higher peaks in knee adduction moment in early stance. Conversely, those with valgus alignment of the lower extremity had statistically lower peaks in knee adduction moment in early stance. The subjects who had a large toe-out angle and low ankle inversion moment peaks in late stance had significantly lower peaks in knee adduction moment in late stance. These significant (low to moderate) correlations suggest that the limbs with more valgus alignment and those with a toe-out gait exhibited a reduced peak adduction moment at the knee. To verify the reproducibility of the data, gait analysis testing was performed on each lower limb on 2 separate days for each subject. Analysis of variance showed that there was no significant difference between test limbs or test days for each subject. Our results suggest that the alignment of the lower limb and the foot progression angle, which can be readily measured in a clinical setting, can serve as predictors of knee joint loading in healthy individuals. These findings may have important implications for both surgical and nonsurgical treatment of abnormalities of the knee joint.

    View details for Web of Science ID A1996UK21800017

    View details for PubMedID 8648508

  • Knee hyperextension gait abnormalities in unstable knees - Recognition and preoperative gait retraining AMERICAN JOURNAL OF SPORTS MEDICINE Noyes, F. R., Dunworth, L. A., Andriacchi, T. P., Andrews, M., Hewett, T. E. 1996; 24 (1): 35-45

    Abstract

    Five patients with symptomatic knee hyperextension thrusting patterns due to posterolateral ligament complex injury underwent gait analysis before and after a gait retraining program. Patients were trained to avoid knee hyperextension by 1) walking with their knees slightly flexed throughout stance, 2) maintaining ankle dorsiflexion in early stance, and 3) maintaining an erect trunk-hip attitude during stance. Kinematic and kinetic measurements were obtained using automated gait analysis. Four of the five patients significantly reduced hyperextension at the knee and abnormal motion patterns at the hip and ankle. Patients showed increases in knee flexion throughout stance conversions of knee flexion-extension moments to more normal biphasic patterns with a 79% decrease in extension moments at terminal extension, and a 22% decrease in knee adduction moments. Posttraining values also showed a 30% decrease in the calculated medial tibiofemoral loads (P < 0.05). At the hip, there were significant decreases in abduction and adduction moments (36% and 18%, respectively, P < 0.01). Ankle plantar flexion motion decreased significantly by 42% (P < 0.01). Gait retraining can alter the biomechanics of hip, knee, and ankle function to approximately normal levels, and therefore is recommended before ligament reconstruction because abnormal knee motions, if resumed postoperatively, can stretch soft tissue reconstructions.

    View details for Web of Science ID A1996TR33800007

    View details for PubMedID 8638751

  • CHARACTERIZATION OF GAIT PARAMETERS IN ADULT-ONSET MYOTONIC-DYSTROPHY - ABNORMAL HIP MOTION ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION WRIGHT, R. B., Yoder, D. M., Costa, J. L., Andriacchi, T. P. 1995; 76 (1): 33-38

    Abstract

    The gait of five patients with myotonic dystrophy was analyzed using light-emitting diodes and a force plate. When compared with the gait of control subjects, that of myotonics suggested weakness of the tibialis anterior and triceps surae muscles. Although the myotonics showed no evidence of lower-extremity myotonia (delayed muscle relaxation following contraction), or of weakness of the hip or knee musculature, all had striking abnormalities in their hip motion. In contrast to the smooth and consistent extension of the hip throughout stance phase observed during gait in control subjects, the hips of myotonics oscillated irregularly as they progressed through stance phase extension, with considerable variation between legs and during successive strides. Excessive use of hip musculature in an attempt to control the oscillatory hip motion may contribute to the chronic fatigue associated with myotonic dystrophy.

    View details for Web of Science ID A1995QB19700005

    View details for PubMedID 7811171

  • DYNAMICS OF KNEE MALALIGNMENT ORTHOPEDIC CLINICS OF NORTH AMERICA Andriacchi, T. P. 1994; 25 (3): 395-403

    Abstract

    The dynamics of malalignment are based on the combination of the static limb alignment and the dynamics of loading at the knee during walking and other activities of daily living. Dynamic loading at the knee can be influenced by subconscious control of limb position such as foot placement, active muscle contraction, passive soft-tissue stability, as well as the speed of walking. The loads that are generated during these dynamic activities are substantially greater than the loads that can be generated during static postures. Therefore, limb alignment based on static radiographic measurements provides one component to the complete analysis of the factors influencing loading at the knee joint. Loading at the knee joint is an important consideration in the progression of degenerative processes at the knee, as well as in the planning and selection of certain treatment modalities. Dynamic malalignment that occurs during activities such as gait should be considered in evaluating the progression of disease processes as well as the selection of appropriate treatment modalities.

    View details for Web of Science ID A1994NX07100005

    View details for PubMedID 8028883

  • CHONDROCYTE CELLS RESPOND MECHANICALLY TO COMPRESSIVE LOADS JOURNAL OF ORTHOPAEDIC RESEARCH Freeman, P. M., Natarajan, R. N., Kimura, J. H., Andriacchi, T. P. 1994; 12 (3): 311-320

    Abstract

    Many studies have illustrated the effect of mechanical loading on articular cartilage and the corresponding changes in chondrocyte metabolism, yet the mechanism through which the cells respond to loading still is unclear. The purpose of this study was to evaluate the change in shape of chondrocytes under a statically applied uniaxial compressive load. Isolated chondrocytes from rat chondrosarcoma were embedded in 2% agarose gel. Strains of 5, 10, and 15% were applied, and images of the cell were recorded from initial loading to equilibrium (15 minutes). A finite-element model was used to model the experimental setup and to estimate the mechanical properties of the chondrocyte at equilibrium. The transient behavior of the composite in the experiment was analyzed with use of a standard linear viscoelastic model. We found that all cells decreased in cross-sectional area under each of the applied compressive strains. In the finite-element model, the elasticity of the chondrocyte was similar to that of the surrounding agarose gel (4.0 kPa) and had a Poisson's ratio of 0.4. Viscoelastic analysis showed that the chondrocytes contributed a significant viscoelastic component to the behavior of the composite in comparison with the agarose gel alone. If a decrease in cell volume proportional to the decrease in cross-sectional area is assumed, the decrease observed was greater than would be predicted by a passive cellular response due to an equivalent osmotic pressure. This indicates that the chondrocyte may be altering its intracellular composition by cellular processes in response to mechanical loading.

    View details for Web of Science ID A1994NQ51700002

    View details for PubMedID 8207584

  • THE INFLUENCE OF LOAD KNOWLEDGE ON LIFTING TECHNIQUE ERGONOMICS Butler, D., Andersson, B. J., TRAFIMOW, J., Schipplein, O. D., Andriacchi, T. P. 1993; 36 (12): 1489-1493

    Abstract

    The purpose of this study was to analyse the influence of load knowledge on lifting technique. Ten men lifted a box containing either no weight or weights of 150, 250 or 300 N with and without knowledge of what was inside the box. The kinetics and kinematics of the lift were analysed using a force plate, an optoelectronic motion analysis system, and a rigid body link model. At 0 N lifting, the unknown load resulted in a jerk-like motion and a significantly increased peak L5-S1 flexion-extension moment. At 150 N there was also a significant increase in the speed of trunk extension with unknown weights, but the L5-S1 moment remained unchanged. At higher load levels there were only minor differences between lifting techniques when knowing and not knowing the load. We conclude that lifts are approached assuming a certain weight, and that when the assumption is wrong and the load lighter than anticipated lifting is performed with a 'jerking' motion, creating unnecessary loads on the lower back.

    View details for Web of Science ID A1993MK99800004

    View details for PubMedID 8287855

  • Functional analysis of pre and post-knee surgery: total knee arthroplasty and ACL reconstruction. Journal of biomechanical engineering Andriacchi, T. P. 1993; 115 (4B): 575-581

    Abstract

    This paper examines the biomechanics of total knee arthroplasty as a treatment for arthritis and anterior cruciate ligament (ACL) reconstruction for repair of torn anterior cruciate ligaments of the knee. These are two of the most frequent reconstructive procedures for the knee joint. Functional testing of patients while performing various activities of daily living was used to study the relationship between the intrinsic biomechanics of the knee and function. The results of the study of patients following total knee replacement demonstrated a dynamic interaction between the posterior cruciate ligament and quadriceps function during stairclimbing. The study of patients with ACL-deficient knees demonstrated that loss of the anterior cruciate ligament can cause the avoidance of quadriceps contraction during activities when the knee is near full extension. Other studies demonstrated a relationship between tibiofemoral joint mechanics and patellofemoral mechanics. In addition, the importance of combined ligamentous laxity with higher than normal adduction moments during gait was examined in relationship to progressive degenerative changes to the medial compartment of the knee. In summary, functional testing such as gait analysis has proven to be an important basic research tool as well as extremely effective for clinical testing of new procedures and devices.

    View details for PubMedID 8302044

  • STEM CURVATURE AND LOAD ANGLE INFLUENCE THE INITIAL RELATIVE BONE-IMPLANT MOTION OF CEMENTLESS FEMORAL STEMS JOURNAL OF ORTHOPAEDIC RESEARCH Berzins, A., Sumner, D. R., Andriacchi, T. P., Galante, J. O. 1993; 11 (5): 758-769

    Abstract

    A 6 df measurement system was used to investigate the initial relative bone-implant motion of two types of cementless total hip replacement femoral components-a straight stem and a curved stem. Five pairs of fresh frozen femurs from human cadavers were tested with loads applied to the femoral head at angles characteristic of level walking, stair-climbing, and rising from a chair. The most important findings were that (a) the resultant proximal translations were twice as high with the straight stem as with the curved stem at load angles encountered in stair-climbing and rising from a chair, (b) both stem types had more motion at load angles encountered in stair-climbing and rising from a chair than in level walking, with the increases ranging from 3 to 14-fold, (c) there was as much as 66-fold more motion distally than proximally, and (d) the amount of interface motion varied by 5-fold between the medial and lateral surfaces of the distal part of the implant because of the combined effects of translation and rotation. The amount of initial bone-implant motion of the femoral component was found to be particularly sensitive to off-axis loading; this suggests that stair-climbing and rising from a chair should be avoided in the early postoperative period when a cementless porous-coated femoral stem has been used.

    View details for Web of Science ID A1993ME48600017

    View details for PubMedID 8410476

  • EFFECT OF PIROXICAM ON GAIT IN PATIENTS WITH OSTEOARTHRITIS OF THE KNEE ARTHRITIS AND RHEUMATISM Schnitzer, T. J., Popovich, J. M., Andersson, G. B., Andriacchi, T. P. 1993; 36 (9): 1207-1213

    Abstract

    To determine whether the use of a nonsteroidal antiinflammatory drug (NSAID) in patients with painful osteoarthritis (OA) of the knee would result in alterations in specific biomechanical parameters of gait.Eighteen patients with symptomatic knee OA and varus knee deformity underwent initial clinical evaluation for pain and activities of daily living, and assessment of parameters of gait utilizing a well-described computerized system. All patients were then treated with piroxicam at 20 mg once daily, and clinical and gait analyses were repeated after 4 weeks.Fifteen of the 18 patients studied had a significant increase in the knee adduction moment after treatment. In the group as a whole there was a significant increase in knee adduction moment (mean percent body weight times height [%BWTH] 4.11 pretreatment versus 4.57 after 4 weeks of treatment; P < 0.01) and maximum quadriceps moment (mean %BWTH 2.13 pretreatment, 2.62 posttreatment; P < 0.01), as well as changes in other gait parameters that might be expected to be altered as a result of relief of pain. Sixteen of 18 patients experienced symptomatic relief, with a significant reduction in pain in the group as a whole after 4 weeks (P < 0.001).NSAID treatment in patients with knee OA results in a reduction in symptomatic pain and an increase in loading of the knee. Whether the increased loading is due to the analgesic effects of the treatment is unknown, but if so, the development of agents capable of relieving pain while reducing loads at the knee may be desirable.

    View details for Web of Science ID A1993MB21100004

    View details for PubMedID 8216414

  • FUNCTIONAL TESTING IN THE ANTERIOR CRUCIATE LIGAMENT-DEFICIENT KNEE CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Andriacchi, T. P., BIRAC, D. 1993: 40-47

    Abstract

    Functional testing of patients with anterior cruciate ligament (ACL) deficient knees and normal subjects during stressful activities such as running to a cut and running to a stop and during activities common to daily life, such as walking, stair climbing, and jogging, is presented. Analysis focused on the application of these tests to treatment planning and clinical evaluation. Functional testing during stressful activities indicates that some patients with ACL-deficient knees have higher than normal net hamstring moments during the early phase of these activities. These results suggest dynamic muscular substitution using the hamstrings in patients with chronic ACL-deficient knees. Patients tested during less stressful activities, such as walking and stair climbing, also demonstrated substantial differences from ACL-intact subjects. The majority of patients tended to reduce the net quadriceps moment when the knee was near full extension. Approximately 75% of the patients who were ACL-deficient developed this type of adaptation, which appears to be a subconscious method of avoiding the net anterior pull of the quadriceps mechanism when the knee is near full extension. Functional testing of the ACL-deficient knee provides meaningful information that cannot be obtained by simpler clinical tests. This information can be extremely useful in the selection and evaluation of patients with certain treatment modalities, since it seems to be directly related to some patients' ability to functionally adapt to the loss of the ACL.

    View details for Web of Science ID A1993KW03600006

    View details for PubMedID 8458153

  • THE ANTERIOR CRUCIATE LIGAMENT-DEFICIENT KNEE WITH VARUS ALIGNMENT - AN ANALYSIS OF GAIT ADAPTATIONS AND DYNAMIC JOINT LOADINGS AMERICAN JOURNAL OF SPORTS MEDICINE Noyes, F. R., Schipplein, O. D., Andriacchi, T. P., Saddemi, S. R., Weise, M. 1992; 20 (6): 707-716

    Abstract

    Thirty-two patients with an ACL-deficient knee and lower limb varus alignment and 16 healthy controls were analyzed during level walking using a force-plate and optoelectronic system. The forces and moments of the lower limb and knee joint were measured and knee joint loads and ligament tensile forces were calculated using a mathematical model. The majority of patients (20 of 32) had an abnormally high adduction moment at the affected knee. The adduction moment showed a statistically significant correlation to high medial tibiofemoral compartment loads and high lateral soft tissue forces, but not to the degree of varus alignment on standing roentgenograms. Fifteen of 32 knees had abnormally high lateral soft tissue forces. We interpreted these gait findings as indicative of a medial shift in the center of maximal joint pressure and an increase in lateral soft tissue forces to achieve coronal plane stability. Further, there is the likelihood of separation of the lateral tibiofemoral joint and "condylar lift-off" during periods of the stance phase. If this occurs, all of the load-bearing forces would shift to the medial tibiofemoral joint and relatively large tensile forces would occur in the lateral soft tissue restraints. The flexion moment, as related to the quadriceps muscle force, was significantly lower than the control knees in 40% of the involved knees, and the extension moment, as related to the hamstring muscle force, was significantly higher in 50% of the involved knees. We interpret this finding as a gait adaptation tending to diminish quadriceps muscle activity and enhance hamstring muscle activity to provide dynamic anteroposterior stability of the knee joint. The fundamental assumption of this paper is that any combination of conditions leading to higher medial joint forces is associated with factors leading to more rapid degeneration of the medial compartment in patients with ACL deficiency, varus deformity, and lax lateral ligaments.

    View details for Web of Science ID A1992JY69700012

    View details for PubMedID 1456365

  • FORCE DISPLACEMENT CHARACTERISTICS OF THE POSTERIOR CRUCIATE LIGAMENT AMERICAN JOURNAL OF SPORTS MEDICINE Bach, B. R., DALUGA, D. J., MIKOSZ, R., Andriacchi, T. P., Seidl, R. 1992; 20 (1): 67-72

    Abstract

    The percent force changes in the posterior cruciate ligament were calculated using a previously validated computerized knee model after the femoral insertion sites were varied 2.5 and 5.0 mm in an anterior, posterior distal, anterior distal, and posterior distal direction. The tibial insertion sites were also varied 2.5 and 5.0 mm in the medial, lateral, proximal, and distal directions. Percent force changes were measured over a range of 0 degree to 90 degrees. These insertion sites simulated potential surgical placement errors. Results of this study demonstrated that the greatest percent force changes in the posterior cruciate ligament were at full extension. The greatest absolute percent force change between 0 degree and 90 degrees of flexion was with a femoral insertion of the posterior cruciate ligament placed 5 mm anterior to its normal attachment site, which resulted in a 39% change in the posterior cruciate ligament force. Distal femoral site attachment had the least effect (10% at 5.0 mm). Alterations at the tibial attachment site were less sensitive than on the femur; the greatest absolute percent force changes occurred with medial and lateral attachment sites (14% and 15%, respectively, at 5.0 mm). A minimal amount of percent force changes were seen between 45 degrees and 75 degrees of knee flexion in all positions tested for both tibial and femoral attachment sites. This model suggests that, like the anterior cruciate ligament, the force in the posterior cruciate ligament is also sensitive to attachment site position. As in anterior cruciate ligament studies, the femoral attachment site was found to be more sensitive.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1992HB59300016

    View details for PubMedID 1554076

  • A relationship between stem orientation and function following total hip arthroplasty. journal of arthroplasty Hodge, W. A., Andriacchi, T. P., Galante, J. O. 1991; 6 (3): 229-235

    Abstract

    A retrospective gait analysis of patients with cemented Charnley-Mueller total hip arthroplasties was conducted to determine if functional differences exist between patients with femoral stems placed in varus and valgus orientations. Twenty patients and ten normals were studied using gait analysis to quantify joint motion and moments during level walking. In addition, a radiographic analysis of stem placement and mechanics of the reconstructed hip was performed on the total hip patients. All patients selected for the study had excellent clinical results on the basis of a score of 95 or better on the Harris hip rating form. The patients were divided into two subgroupings on the basis of stem orientation. A valgus group was defined as having a valgus stem orientation relative to the femoral shaft, with the femoral head-shaft offset shortened by 5 mm or greater compared to the contralateral unoperated hip, while the varus group was defined on the basis of having a varus stem orientation relative to the femoral shaft, with the femoral head-shaft offset restored to normal or greater than normal. A difference in gait was found between the varus and valgus patient groupings. The varus group had abnormal gait characteristics in the range of hip motion, the flexion-extension moments at the hip, and stride length. The patients in the valgus group had statistically normal gait. The differences in the gait characteristics were interpreted as an attempt to alter forces on the hip joint for patients in the varus group. These alterations were possibly an early indication of a subtle adaptation in patients with varus-placed femoral stems since, historically, a greater percentage of the patients in this configuration, retrospectively, go on to mechanical failures.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for PubMedID 1940928

  • INTERACTION BETWEEN ACTIVE AND PASSIVE KNEE STABILIZERS DURING LEVELWALKING JOURNAL OF ORTHOPAEDIC RESEARCH Schipplein, O. D., Andriacchi, T. P. 1991; 9 (1): 113-119

    Abstract

    The gait of normal subjects and patients with varus deformities at the knee was studied by analyzing the interaction between the dynamic (muscular) and passive (ligamentous) restraints affecting lateral stability of the knee. A statistically determinant model predicted that the midstance-phase adducting moment during normal gait would cause lateral knee joint opening if either antagonistic muscle force and/or pretension in the lateral soft tissues were not present at the knee. The patient group tended to compensate for a high midstance-phase adducting moment by walking with a style of gait that demanded more muscle force (greater flexion-extension moments). This walking style reduced the chance of lateral joint opening. It can be speculated that this style of gait would help to maintain equilibrium at the knee. The higher muscle force would aid in resisting the adducting moment, keeping the joint closed laterally and thus increasing the stability of the knee.

    View details for Web of Science ID A1991EP31500013

    View details for PubMedID 1984041

  • Gait adaptations by patients who have a deficient anterior cruciate ligament. journal of bone and joint surgery. American volume BERCHUCK, M., Andriacchi, T. P., Bach, B. R., Reider, B. 1990; 72 (6): 871-877

    Abstract

    Sixteen patients who had unilateral deficiency of the anterior cruciate ligament and ten healthy control subjects were analyzed during level walking, jogging, and ascending and descending stairs. Kinematic and kinetic findings for the right and left hips, knees, and ankles of all of the patients and control subjects were recorded during each activity. Substantial differences from normal function were observed for both limbs of the patients during level walking and during jogging. The magnitude of the maximum moment that tended to flex the knee was reduced the most (140 per cent) during level walking. It was reduced less (30 per cent) during jogging, it was not changed while the patient descended stairs, and it was slightly increased while he or she ascended stairs. The reduction in the magnitude of the flexion moment about the knee was interpreted as the patient's effort to reduce or avoid contraction of the quadriceps. Reduction of the flexion moment reduces any contraction of the quadriceps because there must be a mechanical balance between the external moment (due to body weight and the weight and inertia of the segment of the limb) that tends to flex the knee and an internal moment (generated by contraction of the quadriceps) that tends to extend the knee. This so-called quadriceps-avoidance gait was related to the angle of flexion of the knee when the maximum flexion moment occurred during each activity. This angle of flexion was 20 degrees during walking, 40 degrees during jogging, and approximately 60 degrees during stair-climbing.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for PubMedID 2365720

  • The influence of walking mechanics and time on the results of proximal tibial osteotomy. journal of bone and joint surgery. American volume Wang, J. W., Kuo, K. N., Andriacchi, T. P., Galante, J. O. 1990; 72 (6): 905-909

    Abstract

    The current study describes the influence of the passage of time on the original findings. The mechanisms used by some patients to reduce loading at the knee (adduction moment) also were analyzed. We evaluated the gait of twenty-seven patients (thirty-two knees) who had had a proximal tibial osteotomy for a varus gonarthrosis. Twenty-four patients (twenty-eight knees) returned for follow-up at three to 8.9 years after the osteotomy. This is a follow-up to our original study (Prodromos et al.), which described a relationship between the magnitude of the adduction moment at the knee during walking and the outcome of proximal tibial osteotomy. The patients were divided into low and high adduction-moment groups on the basis of the magnitude of the adduction moment at the knee as measured preoperatively during walking. All fourteen patients in the low adduction-moment group and nine of the fourteen patients in the high adduction-moment group had a good or excellent result. The varus deformity recurred in ten patients in the high adduction-moment group and in three patients in the low adduction-moment group. All of the results degenerated over time. The adaptive mechanism that was used to lower the adduction moment during gait included shortening the stride and toeing-out. The significant correlation between the magnitudes of the inversion moment at the ankle and the adduction moment at the knee suggested that the toe-out gait reduced the adduction moment at the knee.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for PubMedID 2365722

  • A functional and radiographic analysis of the total condylar knee arthroplasty. journal of arthroplasty BRUGIONI, D. J., Andriacchi, T. P., Galante, J. O. 1990; 5 (2): 173-180

    Abstract

    Twenty-one knees in 14 patients were studied during walking, in clinical follow-up, and radiographically. The purpose was to examine the relationship between dynamic loading at the knee joint during level walking in the early postoperative period (1-2 years) and longer-term (4 years) prosthetic performance. Joint kinematics and kinetics were measured while patients were walking in the laboratory. The results were compared with an age-matched control group of healthy normal subjects. Patients were analyzed when grouped according to original diagnoses of rheumatoid or osteoarthritis. After total knee arthroplasty, patients with rheumatoid arthritis walked with a significantly lower magnitude peak adduction moment (force tending to thrust the knee into varus) about the knee than patients with osteoarthritis. The osteoarthritic group had an increased varus axial alignment when compared to the rheumatoid group. There was a strong correlation between postoperative varus alignment and the magnitude of the adduction moment. These results suggest that dynamic loading at the knee is greatly affected by static alignment of the joints in patients with total knee arthroplasty. In spite of the lower adduction moment during level walking and its associated effects on lower compressive loads at the knee, the patients with rheumatoid arthritis had a significantly higher radiolucency index. Thus, it appears that quality of bone stock may be a more important factor in determining prosthetic loosening than dynamic loading at the knee joint following total knee arthroplasty.

    View details for PubMedID 2358816

  • RELATIONSHIP BETWEEN MOMENTS AT THE L5-S1 LEVEL, HIP AND KNEE-JOINT WHEN LIFTING JOURNAL OF BIOMECHANICS Schipplein, O. D., TRAFIMOW, J. H., Andersson, G. B., Andriacchi, T. P. 1990; 23 (9): 907-912

    Abstract

    A study was performed to determine the influence of load magnitude on the self selected technique of lifting. Specifically, it was hypothesized that with heavier weights a tendency would occur to lift more with the back and less with the legs. Flexion-extension moments at the L5/S1 level, hip and knee joints were calculated for subjects when lifting boxes weighing from 50 to 250 N. Lifts were performed using a freestyle technique at normal speed. The moment profiles (moment plotted vs time) were analyzed kinematically and as a function of the weight lifted. The kinematics of the lift changed as the weight increased. The moment at the L5/S1 level increased with increasing weight, however, the corresponding knee moment decreased. Thus, an inverse relationship was found between the moment at the L5/S1 level and the knee joint moment. An increase in weight lifted was also associated with an increase in the angular velocity at the knee while lifting. Apparently with heavier weights there is a tendency to extend the knees earlier during the lift than with lighter weights, confirming our hypothesis. This explains the reduced knee moment. Our findings lead to the hypothesis that quadriceps muscle strength limits the subjects' ability to lift with their knees flexed.

    View details for Web of Science ID A1990DW84300004

    View details for PubMedID 2211735

  • DYNAMICS OF PATHOLOGICAL MOTION - APPLIED TO THE ANTERIOR CRUCIATE DEFICIENT KNEE JOURNAL OF BIOMECHANICS Andriacchi, T. P. 1990; 23: 99-105

    Abstract

    The analysis of the dynamics of pathological motion can provide new and meaningful knowledge about musculoskeletal disorders. The application of the study of pathological ambulation to the analyses of clinical problems is analyzed and discussed. The importance of the selection of appropriate measurement protocols and variable selection is illustrated using an example of the evaluation of patients with an anterior cruciate deficient knee. In particular, the importance of the joint moment as a measure of normal and pathological ambulation is described. An example is provided from a study based on the analysis of 16 patients with unilateral anterior cruciate deficiency. Patients were studied during walking, jogging and ascending and descending stairs. The results are used to demonstrate the importance of testing activities of the knee (e.g. walking, jogging, stair-climbing) that stress the knees during different ranges of motion in order to differentiate functional adaptation associated with the anterior cruciate deficient knee. Results demonstrate that functional abnormalities occur during low stress activities such as level walking. Further, it appears that the functional adaptation occurring during these activities is associated with the anterior force generated on the tibia when the quadriceps contract and the knee is near full extension. It appears that locomotion patterns are reprogrammed to produce an adaptive gait in the majority of patients with anterior cruciate deficient knees.

    View details for Web of Science ID A1990EV30400010

    View details for PubMedID 2081748

  • Evaluation of surgical procedures and/or joint implants with gait analysis. Instructional course lectures Andriacchi, T. P. 1990; 39: 343-350

    View details for PubMedID 2186121

  • THE INFLUENCE OF CHAIR HEIGHT ON LOWER-LIMB MECHANICS DURING RISING JOURNAL OF ORTHOPAEDIC RESEARCH Rodosky, M. W., Andriacchi, T. P., Andersson, G. B. 1989; 7 (2): 266-271

    Abstract

    The mechanics of the lower limb were analyzed in young, adult normal subjects when rising from a seated position. Limb mechanics were described in terms of flexion-extension motion and moments at the hip, knee and ankle while rising from four seat heights corresponding to 65, 80, 100, and 115% of the subject's knee joint height. The results indicate that the maximum moment tending to flex the hip joint was higher than that occurring at the knee or ankle. The magnitude of the maximum flexion moment at the hip was not substantially influenced by chair height, changing by less than 12% between the highest and lowest chair heights. Conversely, the maximum knee flexion moments were found to be highly dependent on chair height and nearly doubled from the highest to the lowest position. The magnitude of the moments at the ankle did not change with chair height and were significantly lower than the magnitude of the moments found during normal walking. The magnitude of motion and moments at the hip were greater during chair-rising than during stair-climbing or walking. The range of motion required at the knee for the lower chair heights was also greater than was reported during stair-climbing studies. Thus, the combination of moments in joint angles during chair-rising are unique among common activities of daily living and should be considered in chair selection as well as in the guidelines for prosthetic devices.

    View details for Web of Science ID A1989T300200014

    View details for PubMedID 2918425

  • COMPUTED TOMOGRAPHIC MEASUREMENT OF CORTICAL BONE GEOMETRY JOURNAL OF BIOMECHANICS Sumner, D. R., Olson, C. L., Freeman, P. M., LOBICK, J. J., Andriacchi, T. P. 1989; 22 (6-7): 649-653

    Abstract

    In this study digital images of bone cross-sections obtained by computed tomography were analyzed with an automated outlining method. It was shown that unbiased cross-sectional geometric measurements of cortical bone could be obtained if the periosteal and endosteal surfaces were defined at separate thresholds. Use of different threshold levels for these two surfaces resulted in errors of 2.6% for periosteal diameters, 7.4% for endosteal diameters and 7.3% for cortical area. If incorrect thresholds were used, cortical thickness measurements can have errors as high as 30%. In addition, simulated variation in medullary fat content did not affect measurement of medullary dimensions.

    View details for Web of Science ID A1989CA09200015

    View details for PubMedID 2808447

  • RELATIONSHIP BETWEEN DYNAMIC DEFORMITIES AND JOINT MOMENTS IN CHILDREN WITH CEREBRAL-PALSY JOURNAL OF PEDIATRIC ORTHOPAEDICS Lai, K. A., Kuo, K. N., Andriacchi, T. P. 1988; 8 (6): 690-695

    Abstract

    A relationship between dynamic flexion-extension motion ranges during walking and the magnitude of flexion and extension moments was analyzed for 38 ambulatory children with spastic cerebral palsy. Moments tending to flex the hip and the knee were more than a factor of two times greater than those occurring during normal gait. At the knee, the magnitude of the moments was related to the amount of flexion deformity, whereas at the hip there was no correlation between moment magnitude and extension motion range. The maximum dorsiflexion and plantarflexion ankle moments were of less than normal value in all deformity groupings. An understanding of the longterm influence of these abnormal moments on the terms of the progression or stabilization of the dynamic deformities during walking is an important step toward improving our understanding of and, potentially, our ability to treat patients with cerebral palsy.

    View details for Web of Science ID A1988Q655600012

    View details for PubMedID 3192697

  • PATELLAR COMPONENT FAILURE IN CEMENTLESS TOTAL KNEE ARTHROPLASTY CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Rosenberg, A. G., Andriacchi, T. P., Barden, R., Galante, J. O. 1988: 106-114

    Abstract

    One hundred twenty-two total knee arthroplasties were performed with porous ingrowth fixation of the patellar component between February 1984 and February 1987. Twelve subsequently have experienced fatigue fracture of the patellar component at the peg-plate junction. All fractured patellar components demonstrated excellent ingrowth and fixation of the porous titanium fiber mesh-peg surfaces with no ingrowth into the porous plate underlying the polyethylene patellar surface. While the initial group of 122 arthroplasties was only slightly greater than one-third male, the preponderance of patellar fractures was in males (ten of 12). Patients with patellar component failure were on average younger and heavier and had a greater range of knee motion than the index group. The average time from implantation to recognition of fracture was 24 months. Biomechanical analysis of the force system about a domed patella demonstrated that loading of the patellofemoral joint results in eccentric loading of the dome surface. Peg fixation not accompanied by fixation of the overlying plate allows these high eccentric forces to load the peg-plate junction in shear with consequent fatigue at the peg-plate junction. These results indicate that the shear forces are sufficiently high to warrant caution in the use of peg-plate systems in which peg ingrowth without plate ingrowth occurs.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1988R039800012

    View details for PubMedID 3180561

  • INFLUENCE OF DYNAMIC FACTORS AND EXTERNAL LOADS ON THE MOMENT AT THE LUMBAR SPINE IN LIFTING SPINE BUSECK, M., Schipplein, O. D., Andersson, G. B., Andriacchi, T. P. 1988; 13 (8): 918-921

    Abstract

    Flexion-extension moments occurring at the L5-S1 level of the spine were calculated when subjects lifted a box weighing from 50 to 250 N. Lifting was performed at normal and fast speed, and the lifts were performed using a freestyle and a leglifting technique. The peak moment increased linearly with increasing load. The moment/load relationship was significantly influenced by lifting speed, and a higher moment occurred at each load level when lifting fast. Lifting speed was reduced when the external load was increased, particularly when the load was 150 N and higher. Moments when lifting using the leglifting technique were lower than when lifting freestyle.

    View details for Web of Science ID A1988Q612900009

    View details for PubMedID 3187716

  • Biomechanics and gait analysis in total knee replacement. Orthopaedic review Andriacchi, T. P. 1988; 17 (5): 470-473

    Abstract

    A primary goal of total knee replacement has been the relief of pain. As new implant designs evolve and other improvements take place, we must broaden our goals to include increased longevity and an improvement in patient function, especially among younger patients. There is a relationship between the longevity of the implant and patient function, since function determines loads on the joint and the motion of the joint. In addition, ultimate breakdown of the prosthesis depends upon these same loads. This paper will first discuss the relationship between function and some of the intrinsic mechanics of the knee joint, and then the relationship between function and mechanics and the longevity of the implant. It is based on an analysis of patients with a variety of differently designed total knee replacements that replicate, to a greater or lesser degree, the anatomy of the knee joint. Some of the implants sacrifice both anterior and posterior cruciates, and some retain both.

    View details for PubMedID 3174215

  • MODEL ANALYSIS OF FACTORS INFLUENCING THE PREDICTION OF MUSCLE FORCES AT THE KNEE JOURNAL OF ORTHOPAEDIC RESEARCH MIKOSZ, R. P., Andriacchi, T. P., Andersson, G. B. 1988; 6 (2): 205-214

    Abstract

    A three-dimensional stochastic mathematical muscle model of the knee joint has been developed and applied to a study in which the influence of both mechanical and physiological factors were examined in relation to the prediction of muscular forces about the joint. The model includes a representation of the proximal portion of the tibia and distal portion of the femur along with a mathematical expression of the patellar mechanism and 13 muscles crossing the knee joint. The model accounts for the rolling and gliding movement of the tibial-femoral articulation. The computational technique involves equilibrating three components of external moments at the knee joint to the internal moments generated by muscular forces and soft tissue. The variables contained in the moment equilibrium equation are randomly chosen based on the choice of the tibial-femoral contact point. The randomness of the variables, reflected in the final solution, defines a stochastic process in the context of the present model. Studies with the model indicated that a very important mechanical aspect of the model was the capability to simulate the moving contact point between the tibia and femur. The moving contact point increased the mechanical advantage of the quadriceps muscles by 50%, which corresponded to in vivo EMG measurements. Muscle force predictions during normal gait have shown the capability of the model to determine the presence of synergistic and antagonistic muscle action.

    View details for Web of Science ID A1988M409700006

    View details for PubMedID 3278080

  • INFLUENCE OF DYNAMIC FACTORS ON THE LUMBAR SPINE MOMENT IN LIFTING ERGONOMICS BUSHJOSEPH, C., SCHIPPLEIN, O., Andersson, G. B., Andriacchi, T. P. 1988; 31 (2): 211-216

    View details for Web of Science ID A1988M956800005

    View details for PubMedID 3371330

  • Retention of the posterior cruciate in total knee arthroplasty. journal of arthroplasty Andriacchi, T. P., Galante, J. O. 1988; 3: S13-9

    Abstract

    Retention of the posterior cruciate ligament in total knee arthroplasty is discussed in biomechanical and clinical terms and the implications for design, kinematics, function, and prosthesis longevity considered. The specific roles of passive range of motion, femoral rollback, stresses on the implant-bone-prosthesis cement system, and wear are examined. The authors argue that the posterior cruciate ligament improves passive range of motion, the mechanical efficiency of the knee musculature and thus improved stairclimbing efficiency, reduces stress at the cement-bone-implant interfaces, and has little or no impact on the polyethylene wear problems.

    View details for PubMedID 3199135

  • INTERACTION BETWEEN INTRINSIC KNEE MECHANICS AND THE KNEE EXTENSOR MECHANISM JOURNAL OF ORTHOPAEDIC RESEARCH Draganich, L. F., Andriacchi, T. P., Andersson, G. B. 1987; 5 (4): 539-547

    Abstract

    The ability of the quadriceps muscles to extend the knee was studied relative to the intrinsic mechanical features of the knee joint. The quadriceps mechanical efficiency changed by nearly 50% between 0 and 90 degrees of knee flexion. The peak efficiency occurred at approximately 20 degrees of knee flexion. The mechanical efficiency of the quadriceps was dependent on the movement of the net anteroposterior (AP) tibiofemoral contact center of pressure, the change in patellar ligament angle, and the change in the quadriceps-to-ligament force transfer ratio. The average net AP tibiofemoral contact center of pressure moved posteriorly on the tibial plateau as the knee flexed from 0 to 90 degrees. The excision of both cruciate ligaments reversed the posteriorly directed movement of the net AP tibiofemoral contact center of pressure at flexion angles from 60 to 90 degrees, resulting in a reduction in extension moment.

    View details for Web of Science ID A1987L138700008

    View details for PubMedID 3681528

  • Knee biomechanics and total knee replacement. journal of arthroplasty Andriacchi, T. P., STANWYCK, T. S., Galante, J. O. 1986; 1 (3): 211-219

    Abstract

    The biomechanics of the knee joint provide an important basis for the rationale in the design and selection of appropriate total knee arthroplasty. This article examines knee biomechanics in terms of patient function, prosthesis design, cruciate ligament retention, alignment, and fixation of the tibial component. While design and surgical technique for total knee replacement progress, a better understanding of the characteristics of joint loading, stress distribution, and the biologic response of bone to stress will provide the potential to improve both function and implant longevity.

    View details for PubMedID 3559597

  • Factors influencing walking and stairclimbing following unicompartmental knee arthroplasty. journal of arthroplasty Weinstein, J. N., Andriacchi, T. P., Galante, J. 1986; 1 (2): 109-115

    Abstract

    The authors quantitatively evaluated the relationship between component placement, limb alignment, and function following unicompartmental knee replacement surgery. It was found that anatomic alignment, prosthetic positioning, and prosthetic design influence the patients' ability to walk and climb stairs. There was wide variation in the placement of the tibial and femoral component among patients. The placement of the femoral component corresponded directly to function during stairclimbing and level walking. Anterior malpositioning of the femoral component resulted in reduced ability to climb stairs. The tibial component position varied primarily in varus-valgus position. Varus-valgus alignment in the frontal plane correlated directly with the magnitude of the adduction moment during level walking. A varus alignment produced a twofold increase in the magnitude of the adduction moment at the knee during walking. Given the potential advantages of the unicompartmental knee, improved precision in component placement should improve the long-term results of hemiarthroplasty knee surgery.

    View details for PubMedID 3559579

  • A relationship between gait and clinical changes following high tibial osteotomy. journal of bone and joint surgery. American volume PRODROMOS, C. C., Andriacchi, T. P., Galante, J. O. 1985; 67 (8): 1188-1194

    Abstract

    We studied the cases of twenty-one patients with high tibial osteotomy in order to determine the relationship between knee-joint loading during gait and clinical outcome. The patients were tested before surgery, one year after surgery, and again at an average of 3.2 years after surgery. An age-matched group of fifteen control subjects was also studied. The results of this study indicate that certain characteristics of preoperative walking are associated with postoperative clinical results. In particular, the moment tending to adduct the knee joint during walking preoperatively was predictive of postoperative clinical results. The patients were classified into a high adduction-moment group and a low adduction-moment group according to the magnitude of the knee-adduction moment. The adduction moment was reduced in both groups after high tibial osteotomy. However, the average postoperative adduction moments in the low adduction-moment group were still significantly lower than those in the high adduction-moment group. The two groups were indistinguishable on the basis of preoperative knee score, initial varus deformity, immediate postoperative correction, age, and weight. However, at an average 3.2-year follow-up, patients with low preoperative adduction moments had substantially better clinical results than did patients with high adduction moments. The low adduction-moment group had 100 per cent excellent or good clinical results, while only 50 per cent of the patients in the high adduction-moment group had an excellent or good result. Furthermore, there was a significant recurrence of varus deformity in the patients in the high adduction-moment group.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for PubMedID 4055843

  • A study of factors influencing muscle activity about the knee joint. Journal of orthopaedic research Andriacchi, T. P., Andersson, G. B., Ortengren, R., MIKOSZ, R. P. 1984; 1 (3): 266-275

    Abstract

    Several factors influencing the myoelectric activity of muscles surrounding the knee joint were studied using fine-wire monopolar electrodes. The muscles studied included the vastus lateralis, vastus intermedius, rectus femoris, vastus medialis, gracilis, sartorius, biceps femoris, semimembranosus, semitendinosus, tensor fasciae latae, medial head of the gastrocnemius, and lateral head of the gastrocnemius. Muscle activity was measured in response to unidirectional loads tending to flex and extend the knee, and to combined loads of flexion-adduction, flexion-abduction, extension-adduction, and extension-abduction. Results indicate that the individual muscle responses are dependent upon the direction, magnitude, and combination of external moments, as well as on the flexion angle of the knee joint. Muscle response appeared to be influenced by certain intrinsic mechanical characteristics of the knee joint that tend to change the moment arms of the muscles as the knee moves. For example, the substantial changes in quadriceps myoelectric activity with knee flexion, with constant load applied, can be related to the movement of the tibial-femoral contact changing the lever arm of the quadriceps mechanism. This study indicates that the mechanics of the knee joint must be taken into consideration while attempting to interpret or predict the load response of muscles crossing the knee joint.

    View details for PubMedID 6481510

  • MODEL STUDIES OF THE STIFFNESS CHARACTERISTICS OF THE HUMAN KNEE-JOINT JOURNAL OF BIOMECHANICS Andriacchi, T. P., MIKOSZ, R. P., HAMPTON, S. J., Galante, J. O. 1983; 16 (1): 23-29

    Abstract

    A three-dimensional mathematical model of the ligamentous knee joint has been developed and applied to studies of the mechanical response of the knee joint. The model includes a representation of the bony portion of the knee including the proximal tibia, distal femur, soft tissue structure and the contacting surfaces of the medial and lateral condyles. The bony portions of the model are represented by rigid bodies while the soft tissue structures are represented by spring and beam type elements. The model employs the direct stiffness approach from structural mechanics and uses an incremental linearization procedure for the geometric and material non-linearities. Studies with the model indicate that the geometric type non-linearities contribute to the overall non-linear response of the knee joint. It was also found that the load-displacement response of the knee is highly dependent on constraints to coupled degrees of freedom. This finding may be an important consideration when interpreting the results of standard laxity tests at the knee, which by their nature may impose constraints to motion.

    View details for Web of Science ID A1983QE15900003

    View details for PubMedID 6833307

  • THE INFLUENCE OF FEMORAL STEM THICKNESS AND IMPLANTATION TECHNIQUE ON THE STRENGTH OF THE BONE-CEMENT BOND ACTA ORTHOPAEDICA SCANDINAVICA SAVINO, A. W., Andersson, G. B., Andriacchi, T. P., Hampton, S., Galante, J. O. 1982; 53 (1): 23-27

    Abstract

    The influence of stem thickness, stem orientation, and insertion pressure on the strength of a prosthesis-cement-bone system was studied in vitro. Three types of prostheses were used with thick and thin stems, allowing for thick or thin cement envelopes. They were implanted with different stem orientations, and with and without a distal femoral cement plug. They were then loaded in a testing machine until a discontinuity of the load deflection curve occurred. The main factor determining the failure load was the presence of the distal plug. In specimens with plugs the main load at failure was 6.5 N, in specimens without a plug it was 4.8 N (P greater than 0.05). The most stable combination was the thick stem with a thin cement envelope placed in valgus or neutral orientation, and implanted with a distal cement plug. It was concluded that when no plug was present failure occurred at the bone-cement interface; when a plug was present it occurred at the prosthesis-cement interface.

    View details for Web of Science ID A1982NE69200005

    View details for PubMedID 7064678

  • A TECHNIQUE FOR EMBEDDING STRAIN-GAUGES WITHIN CURING BONE-CEMENT JOURNAL OF BIOMECHANICS Draganich, L. F., Andriacchi, T. P., Galante, J. O. 1982; 15 (10): 789-790

    Abstract

    A technique has been described to embed strain gages within curing bone cement. Both open faced and encapsulated strain gages were employed. Using a simple cantilever beam in bending test, the experimentally measured strains were linear over the range of bending strains applied and in good agreement with the calculated theoretical values.

    View details for Web of Science ID A1982PW23900008

    View details for PubMedID 7153232

  • THE INFLUENCE OF TOTAL KNEE-REPLACEMENT DESIGN ON WALKING AND STAIR-CLIMBING JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Andriacchi, T. P., Galante, J. O., FERMIER, R. W. 1982; 64 (9): 1328-1335

    View details for Web of Science ID A1982PU52100008

    View details for PubMedID 7142241

  • THE INFLUENCE OF EARLY WEIGHT-BEARING ON EXPERIMENTAL TOTAL HIP ARTHROPLASTIES IN DOGS CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Gitelis, S., Chen, P. Q., Andersson, G. B., Galante, J. O., ROSTOKER, W., Andriacchi, T. P. 1982: 291-302

    Abstract

    The bone-cement interface is an area of concern in the long-term fixation of endoprostheses. The effect of early weight-bearing on the interface has been discussed as an important parameter influencing the characteristics of the interface. In this study, a total hip arthroplasty was performed in two groups of six dogs each. One group was allowed immediate weight-bearing, while in the other, a knee disarticulation amputation was done to prevent weight-bearing. Three animals of each group were killed at three months and three of each group at six months, and a histological study of the interface was done. No morphologic difference was observed between weight-bearing and nonweight-bearing animals in the interface area. Endosteal bone remodeling occurred regardless of weight-bearing stresses. A fibrous membrane was found between the cement and the endosteal surface of the femur, and membrane thickness was similar in all animals. The membrane between the cement and acetabular bone, however, was consistently thicker. Quantitative studies revealed increased femoral cortical bone resorption in the nonweight-bearing animals.

    View details for Web of Science ID A1982PF82300041

    View details for PubMedID 7105589

  • CORRELATIONS BETWEEN CHANGES IN GAIT AND IN CLINICAL STATUS AFTER KNEE ARTHROPLASTY ACTA ORTHOPAEDICA SCANDINAVICA Andersson, G. B., Andriacchi, T. P., Galante, J. O. 1981; 52 (5): 569-573

    Abstract

    Twenty-six knee arthroplastics in 22 subjects were studied clinically and in a gait laboratory before and on one or more occasions after surgery. The purpose was to identify changes in gait characteristics and relate them to changes in the clinical situation of the patients. The gait patterns of the patients changed following surgery mainly with respect to their time-distance characteristics; stride length, cadence, time of swing, and time of support. Positive correlations were noted between these gait changes and the patient's pain, his limp, and his walking distance. It is concluded that the information obtained in sophisticated gait laboratory is of limited value to the surgeon in his clinical assessment.

    View details for Web of Science ID A1981MT38600015

    View details for PubMedID 7331794

  • CHANGES IN THE GAIT PATTERNS OF GROWING CHILDREN JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Beck, R. J., Andriacchi, T. P., Kuo, K. N., FERMIER, R. W., Galante, J. O. 1981; 63 (9): 1452-1457

    Abstract

    We observed the gait patterns, including time and distance measurements and ground reaction forces, of fifty-one normal children. Thirty-three children were retested once at one, three, six, nine, or twelve months, over a two-year period, for a total of eighty-four gait observations. Time and distance measurements and foot-ground reaction force measurements were found to be dependent on walking speed and the age of the child. An increase in height with age was found to be the major factor in determining the changes in time and distance measurements with age. For example, we found that average stride length was 76 per cent of the child's height at a walking speed of 1.04 meters per second regardless of the child's age. In contrast, the three components of foot-ground reaction force (vertical, lateral, and forward directions) were observed to vary with age up to five years even when normalized. After the age of five years an adult pattern of ground reaction force emerged. In addition, we found that walking patterns of children who were more than found years old did not vary when retested within a three-month period. However, for children less than four years old, measurements were found to change due to growth during the three-month period to retesting. Similar changes due to growth were found in children more than four years old who were tested at intervals more than three months apart. This important finding may be clinically useful in the study of the effects of treatment.

    View details for Web of Science ID A1981MY01200012

    View details for PubMedID 7320036

  • 3-DIMENSIONAL STRESS-ANALYSIS OF THE FEMORAL STEM OF A TOTAL HIP-PROSTHESIS JOURNAL OF BIOMECHANICS HAMPTON, S. J., Andriacchi, T. P., Galante, J. O. 1980; 13 (5): 443-448

    View details for Web of Science ID A1980JU60000006

    View details for PubMedID 7400172

  • ELECTRONIC MEASUREMENT OF INSTANTANEOUS FOOT-FLOOR CONTACT PATTERNS DURING GAIT JOURNAL OF BIOMECHANICS Draganich, L. F., Andriacchi, T. P., Strongwater, A. M., Galante, J. O. 1980; 13 (10): 875-880

    View details for Web of Science ID A1980KS08300007

    View details for PubMedID 7462261

  • A STUDY OF LOWER-LIMB MECHANICS DURING STAIR-CLIMBING JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Andriacchi, T. P., Andersson, G. B., FERMIER, R. W., Stern, D., Galante, J. O. 1980; 62 (5): 749-757

    Abstract

    The motions, forces, and moments at the major joints of the lower limbs of ten men ascending and descending stairs were analyzed using an optoelectronic system, a force-plate, and electromyography. The mean values for the maximum sagittalplane motions of the hip, knee, and ankle were 42, 88, and 27 degrees, respectively. The mean maximum net flexion-extension moments were: at the hip, 123.9 newton-meters going up and 112.5 newton-meters going down stairs; at the knee, 57.1 newton-meters going up and 146.6 newton-meters going down stairs; and at the ankle, 137.2 newton-meters going up and 107.5 newton-meters going down stairs. When going up and down stairs large moments are present about weight-bearing joints, but descending movements produce the largest moments. The magnitudes of these moments are considerably higher than those produced during level walking.

    View details for Web of Science ID A1980KB41600008

    View details for PubMedID 7391098

  • PROTHESIS CEMENT ENVELOPE IN FEMORAL COMPONENT TOTAL HIPS SURGICAL FORUM SAVINO, A. W., Andersson, G. B., Andriacchi, T. P., Galante, J. O. 1978; 29: 556-557

    Abstract

    Loading tests showed wide stem-thin cement envelope systems in valgus orientation placed with distal plug to be significantly more stable at higher loads. Narrow stem-thick cement envelope systems in varus without plug were unstable within a marginal factor of safety for cyclic loading. Four cement failures occurred within the thin stem-thick cement system on the upper lateral aspect of the prosthesis cement envelope.

    View details for Web of Science ID A1978GA40500232

    View details for PubMedID 401259

  • WALKING SPEED AS A BASIS FOR NORMAL AND ABNORMAL GAIT MEASUREMENTS JOURNAL OF BIOMECHANICS Andriacchi, T. P., OGLE, J. A., Galante, J. O. 1977; 10 (4): 261-268

    View details for Web of Science ID A1977DG31500006

    View details for PubMedID 858732

  • MILWAUKEE BRACE CORRECTION OF IDIOPATHIC SCOLIOSIS - BIOMECHANICAL ANALYSIS AND A RESTROSPECTIVE STUDY JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Andriacchi, T. P., Schultz, A. B., Belytschko, T. B., DeWald, R. L. 1976; 58 (6): 806-815

    Abstract

    We analyzed the biomechanics of Milwaukee brace treatment of idiopathic scoliotic patients through simulation in five computer-constructed model spines. The contributions to correction of each component of the brace were examined in these model spines, and some of the mechanical principles that determine the outcome of brace treatment were studied. The validity of the stimulation findings was then tested by a retrospective analysis. Simulation was used to predict the outcome of milwaukee brace treatment in sixty-eight patients. In 81 per cent of these patients, the actual outcome agreed with the prediction. The study suggests that careful adherence to mechanical principles in the use of a Milwaukee brace will result in successful treatment of more patients.

    View details for Web of Science ID A1976CF34100011

    View details for PubMedID 956227

  • STRESS ANALYSIS OF FEMORAL STEM IN TOTAL HIP PROSTHESES JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Andriacchi, T. P., Galante, J. O., Belytschko, T. B., Hampton, S. 1976; 58 (5): 618-624

    Abstract

    A two-dimensional stress analysis was used to study the effects of some of the factors leading to early fatigue failure of the femoral stem in total hip prostheses. The results show that loss of proximal stem support at the level of the calcar femorale will result in stem stress levels which can lead to fatigue failure. In addition, the role of body weight and range of cyclic stress fluctuation play an important role in fatigue life under conditions where the stem has lost proximal support. These results indicate that stem design could be improved by incorporating some means of ensuring adequate support at the calcar femoralre maximum tensile stresses are found to occur.

    View details for Web of Science ID A1976BZ29900006

    View details for PubMedID 932061

  • Analog studies of forces in the human spine: computational techniques. Journal of biomechanics Belytschko, T. B., Andriacchi, T. P., Schultz, A. B., Galante, J. O. 1973; 6 (4): 361-371

    View details for PubMedID 4732936

  • Analog studies of forces in the human spine: mechanical properties and motion segment behavior. Journal of biomechanics Schultz, A. B., Belytschko, T. B., Andriacchi, T. P., Galante, J. O. 1973; 6 (4): 373-383

    View details for PubMedID 4732937

  • A study of geometrical relationships in scoliotic spines. Journal of biomechanics Schultz, A. B., LAROCCA, H., Galante, J. O., Andriacchi, T. P. 1972; 5 (4): 409-420

    View details for PubMedID 4666200

Conference Proceedings


  • Studies of human locomotion: past, present and future Andriacchi, T. P., Alexander, E. J. ELSEVIER SCI LTD. 2000: 1217-1224

    Abstract

    The study of human locomotion and its applications are examined from a historical viewpoint. Several critical steps in the advancement of the discipline are considered in the context of addressing a particular need to answer fundamental questions regarding the process of human locomotion. In addition, changes in the methods of observation are discussed in terms of the advancement of the field. As an example, the application of a newly developed point cluster technique to reduce the artifact due to skin movement is described. The method was applied to a study of patients with anterior cruciate ligament (ACL) deficient knees. The results demonstrate that patients with ACL-deficient knees have significantly greater than normal anterior-posterior displacement of the femur relative to the tibia during walking. Many of the advancements in the tools for observation and interpretation have been driven by new demands on our fundamental knowledge. Future advancements in the study of human locomotion will likely be motivated by new treatment modalities that require an in depth understanding of the subtle complexities of human locomotion. Future directions are discussed in the context of new methods for reducing errors associated with skin movement combined with information obtained from other imaging methods, such as magnetic resonance imaging.

    View details for Web of Science ID 000089304700005

    View details for PubMedID 10899330

  • DYNAMIC ANALYSES OF LIFTING Andersson, G. B., Schipplein, O. D., TRAFIMOW, J. H., Andriacchi, T. P. ELSEVIER SCIENCE PUBL B V. 1988: 437-440

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