Bio

Clinical Focus


  • Orthopaedic Surgery
  • Adult Reconstructive Surgery

Academic Appointments


Administrative Appointments


  • Medical Director, Bone and Joint Rehabilitation Research and Development Center (2003 - 2009)
  • Chief, VA Palo Alto Orthopedic Surgery Section (2006 - Present)

Honors & Awards


  • Saul Halpern MD Orthopedic Educator of the Year Award, Department of Orthopedic Surgery (June 2011)
  • Saul Halpern MD Orthopedic Educator of the Year Award, Department of Orthopedic Surgery (June 2009)
  • Saul Halpern MD Orthopedic Educator of the Year Award, Department of Orthopedic Surgery (June 2006)
  • Clinical Biomechanics Award, American Society of Biomechanics (2005)
  • Saul Halpern MD Orthopedic Educator of the Year Award, Department of Orthopedic Surgery (June 2002)

Professional Education


  • Fellowship:Mayo Clinic (2000) AZ
  • Residency:Stanford University School of Medicine (1999) CA
  • Internship:Stanford University School of Medicine (1995) CA
  • Board Certification: Orthopaedic Surgery, American Board of Orthopaedic Surgery (2002)
  • Medical Education:Stanford University School of Medicine (1994) CA
  • MD, Stanford University, Medicine (1994)
  • PhD, Stanford University, Mechanical Engineering (1994)
  • Residency, Stanford Universtity, Orthopedic Surgery (1999)
  • Fellowship, Mayo Clinic, Adult Reconstructive Surgery (2000)

Research & Scholarship

Current Research and Scholarly Interests


Osteoarthritis
Medical Device Development

Teaching

2013-14 Courses


Publications

Journal Articles


  • Component alignment during total knee arthroplasty with use of standard or custom instrumentation: a randomized clinical trial using computed tomography for postoperative alignment measurement. journal of bone and joint surgery. American volume Woolson, S. T., Harris, A. H., Wagner, D. W., Giori, N. J. 2014; 96 (5): 366-372

    Abstract

    Patient-specific femoral and tibial cutting blocks produced with use of data from preoperative computed tomography (CT) or magnetic resonance imaging (MRI) scans have been employed recently to optimize component alignment in total knee arthroplasty. We report the results of a randomized controlled trial in which CT scans were used to compare postoperative component alignment between patients treated with custom instruments and those managed with traditional instruments.The in-hospital data and early clinical outcomes, including Knee Society scores, were determined in a randomized clinical trial of forty-seven patients who had undergone a total of forty-eight primary total knee arthroplasties with patient-specific instruments (twenty-two knees) or standard instruments (twenty-six knees). Orientation of the implants was compared by using three-dimensional CT data.No significant differences were found between the study and control groups with respect to any clinical outcome after a minimum of six months of follow-up. The patient-specific tibial cutting block was abandoned in favor of a standard external alignment jig in seven of the twenty-two study knees because of possible malalignment. A detailed analysis of intent-to-treat and per-protocol groups of study and control knees did not show any significant improvement in component alignment, including femoral component rotation in the axial plane, in the patients treated with the custom instruments. The percentage of outliers-defined as less than -3° or more than 3° from the correct orientation of the tibial slope-was significantly higher in the group treated with use of patient-specific blocks than it was in the control group, in both the intent-to-treat (32% versus 8%, p = 0.032) and the per-protocol (47% versus 6%, p = 0.0008) analysis.There were no significant improvements in clinical outcomes or knee component alignment in patients treated with patient-specific cutting blocks as compared with those treated with standard instruments. The group treated with patient-specific cutting blocks had a significantly higher prevalence of malalignment in terms of tibial component slope than the knees treated with standard instruments.Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

    View details for DOI 10.2106/JBJS.L.01722

    View details for PubMedID 24599197

  • Hemoglobin A1C as a Marker for Surgical Risk in Diabetic Patients Undergoing Total Joint Arthroplasty. journal of arthroplasty Harris, A. H., Bowe, T. R., Gupta, S., Ellerbe, L. S., Giori, N. J. 2013; 28 (8): 25-29

    Abstract

    Diabetes is a risk factor for complications following total joint arthroplasty (TJA). This retrospective cohort study of 6088 diabetic patients from the Veterans Health Administration (VHA) undergoing TJA sought to determine if hemoglobin A1c, an accessible and objective lab value, has utility as a predictor of risk of complications in TJA after controlling for demographic, surgical, and medical center effects, and to evaluate the benefits and risks of alternative thresholds. Analysis of the functional relationship between hemoglobin A1c and complications revealed that the risk linearly increases through, rather than surging at, the threshold of 7%. Before delaying surgery to achieve better diabetic control, surgeons and patients should weigh the estimated risks of TJA against the potential benefits.

    View details for DOI 10.1016/j.arth.2013.03.033

    View details for PubMedID 23910511

  • A Randomized Comparison of Long- and Short-Axis Imaging for In-Plane Ultrasound-Guided Femoral Perineural Catheter Insertion JOURNAL OF ULTRASOUND IN MEDICINE Mariano, E. R., Kim, T. E., Funck, N., Walters, T., Wagner, M. J., Harrison, T. K., Giori, N., Woolson, S., Ganaway, T., Howard, S. K. 2013; 32 (1): 149-156

    Abstract

    Continuous femoral nerve blocks provide effective analgesia after knee arthroplasty, and infusion effects depend on reliable catheter location. Ultrasound-guided perineural catheter insertion using a short-axis in-plane technique has been validated, but the optimal catheter location relative to target nerve and placement orientation remain unknown. We hypothesized that a long-axis in-plane technique for femoral perineural catheter insertion results in faster onset of sensory anesthesia compared to a short-axis in-plane technique.Preoperatively, patients receiving an ultrasound-guided nonstimulating femoral perineural catheter for knee surgery were randomly assigned to either the long-axis in-plane or short-axis in-plane technique. A local anesthetic was administered via the catheter after successful insertion. The primary outcome was the time to achieve complete sensory anesthesia. Secondary outcomes included the procedural time, the onset time of the motor block, pain and muscle weakness reported on postoperative day 1, and procedure-related complications.The short-axis group (n = 23) took a median (10th-90th percentiles) of 9.0 (6.0-20.4) minutes compared to 6.0 (3.0-14.4) minutes for the long-axis group (n = 23; P = .044) to achieve complete sensory anesthesia. Short-axis procedures took 5.0 (4.0-7.8) minutes to perform compared to 9.0 (7.0-14.8) minutes for long-axis procedures (P < .001). In the short-axis group, 19 of 23 (83%) achieved a complete motor block within the testing period compared to 18 of 23 (78%) in the long-axis group (P = .813); short-axis procedures took 12.0 (6.0-15.0) minutes versus 15.0 (5.1-27.9) minutes for long-axis procedures (P = .048). There were no statistically significant differences in other secondary outcomes.Long-axis in-plane femoral perineural catheters result in a slightly faster onset of sensory anesthesia, but placement takes longer to perform without other clinical advantages.

    View details for Web of Science ID 000313607400017

    View details for PubMedID 23269720

  • Prevalence of Hepatitis C Virus Infection in the Veteran Population Undergoing Total Joint Arthroplasty JOURNAL OF ARTHROPLASTY Calore, B. L., Cheung, R. C., Giori, N. J. 2012; 27 (10): 1772-1776

    Abstract

    Many orthopedic surgeons train or are employed at the Department of Veterans Affairs (VA) hospitals. We sought to determine the prevalence of hepatitis C antibody-positive and hepatitis C-viremic patients in the VA population undergoing total joint arthroplasty. In this prospective cohort study, 381 of 408 patients undergoing primary total joint arthroplasty for 22 consecutive months were tested for hepatitis C virus (HCV) infection preoperatively. Thirty-two (8.4%) of 381 patients were positive for hepatitis C virus antibody. Seventeen were actually viremic at the time of total joint arthroplasty (4.5%). The prevalence of detectable hepatitis C antibody in VA patients undergoing total joint arthroplasty is about 6 times the general population (1.3%). Surgeons practicing on populations with a high prevalence of hepatitis C such as this should do all they can to minimize the risk of sharps injury.

    View details for DOI 10.1016/j.arth.2012.05.016

    View details for Web of Science ID 000311583500006

    View details for PubMedID 22770853

  • 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

  • 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

  • The low permeability of healthy meniscus and labrum limit articular cartilage consolidation and maintain fluid load support in the knee and hip JOURNAL OF BIOMECHANICS Haemer, J. M., Carter, D. R., Giori, N. J. 2012; 45 (8): 1450-1456

    Abstract

    The knee meniscus and hip labrum appear to be important for joint health, but the mechanisms by which these structures perform their functions are not fully understood. The fluid phase of articular cartilage provides compressive stiffness and aids in maintaining a low friction articulation. Healthy fibrocartilage, the tissue of meniscus and labrum, has a lower fluid permeability than articular cartilage. In this study we hypothesized that an important function of the knee meniscus and the hip labrum is to augment fluid retention in the articular cartilage of a mechanically loaded joint. Axisymmetric hyperporoelastic finite element models were analyzed for an idealized knee and an idealized hip. The results indicate that the meniscus maintained fluid pressure and inhibited fluid exudation in knee articular cartilage. Similar, but smaller, effects were seen with the labrum in the hip. Increasing the fibrocartilage permeability relative to that of articular cartilage gave a consolidation rate and loss of fluid load support comparable to that predicted by meniscectomy or labrectomy. The reduced articular cartilage fluid pressure that was calculated for the joint periphery is consistent with patterns of endochondral ossification and osteophyte formation in knee and hip osteoarthritis. High articular central strains and loss of fluid load support after meniscectomy could lead to fibrillation. An intact low-permeability fibrocartilage is important for limiting fluid exudation from articular cartilage in the hip and knee. This may be an important aspect of the role of fibrocartilage in protecting these joints from osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2012.02.015

    View details for Web of Science ID 000304216100017

    View details for PubMedID 22391467

  • 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

  • "Not statistically different" does not necessarily mean "the same": the important but underappreciated distinction between difference and equivalence studies. journal of bone and joint surgery. American volume Harris, A. H., Fernandes-Taylor, S., Giori, N. 2012; 94 (5)

    View details for DOI 10.2106/JBJS.K.00568

    View details for PubMedID 22398743

  • Articular cartilage friction increases in hip joints after the removal of acetabular labrum JOURNAL OF BIOMECHANICS Song, Y., Ito, H., Kourtis, L., Safran, M. R., Carter, D. R., Giori, N. J. 2012; 45 (3): 524-530

    Abstract

    The acetabular labrum is believed to have a sealing function. However, a torn labrum may not effectively prevent joint fluid from escaping a compressed joint, resulting in impaired lubrication. We aimed to understand the role of the acetabular labrum in maintaining a low friction environment in the hip joint. We did this by measuring the resistance to rotation (RTR) of the hip, which reflects the friction of the articular cartilage surface, following focal and complete labrectomy. Five cadaveric hips without evidence of osteoarthritis and impingement were tested. We measured resistance to rotation of the hip joint during 0.5, 1, 2, and 3 times body weight (BW) cyclic loading in the intact hip, and after focal and complete labrectomy. Resistance to rotation, which reflects articular cartilage friction in an intact hip was significantly increased following focal labrectomy at 1-3 BW loading, and following complete labrectomy at all load levels. The acetabular labrum appears to maintain a low friction environment, possibly by sealing the joint from fluid exudation. Even focal labrectomy may result in increased joint friction, a condition that may be detrimental to articular cartilage and lead to osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2011.11.044

    View details for Web of Science ID 000300863600017

    View details for PubMedID 22176711

  • EFFECT OF PARTIAL MEDIAL MENISCECTOMY ON THE INTERACTION BETWEEN PRIMARY AND SECONDARY KNEE MOTION DURING GAIT PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B Edd, S. N., Netravali, N. A., Giori, N. J., Andriacchi, T. P. 2012: 1061-1062
  • Nine-Year Incidence of Kidney Disease in Patients Who Have Had Total Hip Arthroplasty JOURNAL OF ARTHROPLASTY Chandran, S. E., Giori, N. J. 2011; 26 (6): 24-27

    Abstract

    Metal-metal total hip arthroplasty (THA) is contraindicated in patients with impaired renal function due to increased metal ion output relative to other bearings and renal excretion of metal ions. Although one can avoid a metal-metal THA in a patient with renal disease, a patient may be destined to develop renal disease later in life. In this study, we sought to determine the incidence of newly diagnosed renal disease in the 9 years after THA. Using the Department of Veterans Affairs national database, we identified 1709 patients who had a primary THA in 2000 without preexisting renal disease. We found the 9-year risk of developing chronic renal disease after primary THA to be 14% and severe or end-stage renal disease to be 6%.

    View details for DOI 10.1016/j.arth.2011.03.016

    View details for Web of Science ID 000294393000006

    View details for PubMedID 21507606

  • Changes in articular cartilage mechanics with meniscectomy: A novel image-based modeling approach and comparison to patterns of OA JOURNAL OF BIOMECHANICS Haemer, J. M., Song, Y., Carter, D. R., Giori, N. J. 2011; 44 (12): 2307-2312

    Abstract

    Meniscectomy is a significant risk factor for osteoarthritis, involving altered cell synthesis, central fibrillation, and peripheral osteophyte formation. Though changes in articular cartilage contact pressure are known, changes in tissue-level mechanical parameters within articular cartilage are not well understood. Recent imaging research has revealed the effects of meniscectomy on the time-dependent deformation of physiologically loaded articular cartilage. To determine tissue-level cartilage mechanics that underlie observed deformation, a novel finite element modeling approach using imaging data and a contacting indenter boundary condition was developed. The indenter method reproduces observed articular surface deformation and avoids assumptions about tangential stretching. Comparison of results from an indenter model with a traditional femur-tibia model verified the method, giving errors in displacement, solid and fluid stress, and strain below 1% (RMS) and 7% (max.) of the absolute maximum of the parameters of interest. Indenter finite element models using real joint image data showed increased fluid pressure, fluid exudation, loss of fluid load support, and increased tensile strains centrally on the tibial condyle after meniscectomy-patterns corresponding to clinical observations of cartilage matrix damage and fibrillation. Peripherally there was decreased consolidation, which corresponds to reduced contact and fluid pressure in this analysis. Clinically, these areas have exhibited advance of the subchondral growth front, biological destruction of the cartilage matrix, cartilage thinning, and eventual replacement of the cartilage via endochondral ossification. Characterizing the changes in cartilage mechanics with meniscectomy and correspondence with observed tissue-level effects may help elucidate the etiology of joint-level degradation seen in osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2011.04.014

    View details for Web of Science ID 000294033200019

    View details for PubMedID 21741046

  • Strains Across the Acetabular Labrum During Hip Motion A Cadaveric Model AMERICAN JOURNAL OF SPORTS MEDICINE Safran, M. R., Giordano, G., Lindsey, D. P., Gold, G. E., Rosenberg, J., Zaffagnini, S., Giori, N. J. 2011; 39: 92S-102S

    Abstract

    Labral tears commonly cause disabling intra-articular hip pain and are commonly treated with hip arthroscopy. However, the function and role of the labrum are still unclear.(1) Flexion, adduction, and internal rotation (a position clinically defined as the position for physical examination known as the impingement test) places greatest circumferential strain on the anterolateral labrum and posterior labrum; (2) extension with external rotation (a position clinically utilized during physical examination to assess for posterior impingement and for anterior instability) places significant circumferential strains on the anterior labrum; (3) abduction with external rotation during neutral flexion-extension (the position the extremity rests in when a patient lies supine) places the greatest load on the lateral labrum.Descriptive laboratory study. Methods: Twelve cadaveric hips (age, 79 years) without labral tears or arthritis were studied. Hips were dissected free of soft tissues, except the capsuloligamentous structures. Differential variable reluctance transducers were placed in the labrum anteriorly, anterolaterally, laterally, and posteriorly to record circumferential strains in all 4 regions as the hip was placed in 36 different positions.The posterior labrum had the greatest circumferential strains identified; the peak was in the flexed position, in adduction or neutral abduction-adduction. The greatest strains anteriorly were in flexion with adduction. The greatest strains anterolaterally were in full extension. External rotation had greater strains than neutral rotation and internal rotation. The greatest strains laterally were at 90° of flexion with abduction, and external or neutral rotation. In the impingement position, the anterolateral strain increased the most, while the posterior labrum showed decreased strain (greatest magnitude of strain change). When the hip is externally rotated and in neutral flexion-extension or fully extended, the posterior labrum has significantly increased strain, while the anterolateral labrum strain is decreased.These are the first comprehensive strain data (of circumferential strain) analyzing the whole hip labrum. For the intact labrum, the greatest strain change was at the posterior acetabulum, whereas clinically, acetabular labral tears occur most frequently anterolaterally or anteriorly. The results are consistent with the impingement test as an assessment of anterolateral acetabular labral stress. The hyperextension-rotation test, often used clinically to assess anterior hip instability and posterior impingement, did not show a change in strain anteriorly, but did reveal an increase in strain posteriorly.Although this study does not include muscular forces across the hip joint, it does provide a clue as to the stresses about the labrum through the complete range of motions of the hip, which may help in providing a better understanding of the cause of labral tears and in the protection of labral repairs.

    View details for DOI 10.1177/0363546511414017

    View details for Web of Science ID 000292167400014

    View details for PubMedID 21709038

  • An Anatomic Arthroscopic Description of the Hip Capsular Ligaments for the Hip Arthroscopist ARTHROSCOPY-THE JOURNAL OF ARTHROSCOPIC AND RELATED SURGERY Telleria, J. J., Lindsey, D. P., Giori, N. J., Safran, M. R. 2011; 27 (5): 628-636

    Abstract

    To examine and describe the normal anatomic intra-articular locations of the hip capsular ligaments in the central and peripheral compartments of the hip joint.Eight paired fresh-frozen human cadaveric hips (mean age, 73.3 years) were carefully dissected free of soft tissue to expose the hip capsule. Needles were placed through the capsule along the macroscopic borders of the hip capsular ligaments. Arthroscopy was performed on each hip, and the relations of the needles, and thus the ligaments, to the arthroscopic portals and other soft-tissue and osseous landmarks in the hip were recorded by use of a clock-face reference system.The iliofemoral ligament (ILFL) ran from 12:45 to 3 o'clock. The ILFL was pierced by the anterolateral and anterior portals just within its lateral and medial borders, respectively. The pubofemoral ligament was located from the 3:30 to the 5:30 clock position; the lateral border was at the psoas-U perimeter, and the medial border was at the junction of the anteroinferior acetabulum and the cotyloid fossa. The ischiofemoral ligament (ISFL) ran from the 7:45 to the 10:30 clock position. The posterolateral portal pierced the ISFL just inside its superior/lateral border, and the inferior/lateral border was located at the posteroinferior acetabulum. In the peripheral compartment the lateral ILFL and superior/lateral ISFL borders were in proximity to the lateral synovial fold. The medial ILFL and lateral pubofemoral ligament borders were closely approximated to the medial synovial fold.The hip capsular ligaments have distinct and consistent arthroscopic locations within the hip joint and are associated with clearly identifiable landmarks in the central and peripheral compartments. The standard hip arthroscopy portals are closely related to the borders of the hip capsular ligaments.These findings will help orthopaedic surgeons know which structures are being addressed during arthroscopic surgery and may help in the development of future hip procedures.

    View details for DOI 10.1016/j.arthro.2011.01.007

    View details for Web of Science ID 000289557700006

    View details for PubMedID 21663720

  • Local infiltration analgesia in TKA patients reduces length of stay and postoperative pain scores. Orthopedics Tripuraneni, K. R., Woolson, S. T., Giori, N. J. 2011; 34 (3): 173-?

    Abstract

    Numerous postoperative pain protocols exist for patients undergoing total knee arthroplasty (TKA). We compared the length of stay, early range of motion (ROM), and pain scores of a control group with a femoral nerve block to those of a group with femoral nerve block and local infiltration analgesia following TKA. In a consecutive series of patients undergoing primary TKA at a Veteran's Administration hospital, 40 patients (40 TKAs) who had local infiltration analgesia were compared to a historical group of 43 patients (43 TKAs) who had a long-acting femoral nerve block without local infiltration analgesia. Local infiltration analgesia consisted of intraoperative injection of 150 mL of 300 mg ropivacaine, 30 mg ketorolac, and 500 ?g epinephrine using 50 mL into each of 3 areas: (1) posterior capsule, (2) medial and lateral capsule, and (3) anterior capsule and subcutaneous tissues. A 17-gauge intra-articular catheter was used to inject an additional 100 mg of ropivacaine on postoperative day 1. The control group had a single-shot femoral nerve block using 150 mg of ropivacaine with epinephrine. Mean length of stay for the local infiltration analgesia group compared to controls was 3.2±1.4 days vs 3.8±1.6 days, respectively (P=.03). No significant differences existed in average ROM (6 weeks), discharge hematocrit, transfusions, and temperature. Mean pain scores were lower in the local infiltration analgesia group on postoperative day 1 (P=.04), but not on postoperative day 2 or 3. Maximum visual analog scale scores (P<.01) were reduced in the local infiltration analgesia group. Our early experience with local infiltration analgesia demonstrated a significantly reduced length of stay due to decreased postoperative pain.

    View details for DOI 10.3928/01477447-20110124-11

    View details for PubMedID 21410125

  • Preoperative alcohol screening scores: association with complications in men undergoing total joint arthroplasty. journal of bone and joint surgery. American volume Harris, A. H., Reeder, R., Ellerbe, L., Bradley, K. A., Rubinsky, A. D., Giori, N. J. 2011; 93 (4): 321-327

    Abstract

    The risks associated with preoperative alcohol misuse by patients before undergoing total joint arthroplasty are not well known, yet alcohol misuse by surgical patients is common and has been linked to an increased risk of complications after other procedures. The purpose of this study was to evaluate the association between a patient's preoperative standardized alcohol-misuse screening score and his or her risk of complications after total joint arthroplasty.The Alcohol Use Disorders Identification Test-Consumption (AUDIT-C) is an alcohol-misuse screening instrument administered annually to all patients receiving care through the Veterans Health Administration (VHA). The scores range from 0 to 12, with higher scores signifying greater and more frequent consumption. In a study of 185 male patients who had alcohol screening scores recorded in the year preceding surgery at a Palo Alto VHA facility, and who reported at least some alcohol use, we estimated the association between preoperative screening scores and the number of surgical complications in an age and comorbidity-adjusted regression analyses.Of the 185 patients reporting at least some drinking in the year before their total joint replacement, 17% (thirty-two) had an alcohol screening score suggestive of alcohol misuse; six of those thirty-two patients had one complication, four had two complications, and two had three complications. The screening scores were significantly related to the number of complications in a negative binomial regression analysis (exp[β] = 1.29, p = 0.035), which demonstrated a 29% increase in the expected number of complications with every additional point of the screening score above 1, although with wide confidence intervals for the higher scores.Complications following total joint arthroplasty were significantly related to alcohol misuse in this group of male patients treated at a VHA facility. The AUDIT-C has three simple questions that can be incorporated into a preoperative evaluation and can alert the treatment team to patients with increased postoperative risk. Preoperative screening for alcohol misuse, and perhaps preoperative counseling or referral to treatment for heavy drinkers, may be indicated for patients who are to undergo total joint arthroplasty.

    View details for DOI 10.2106/JBJS.I.01560

    View details for PubMedID 21325583

  • Femoral Fracture After Harvesting of Autologous Bone Graft Using a Reamer/Irrigator/Aspirator JOURNAL OF ORTHOPAEDIC TRAUMA Giori, N. J., Beaupre, G. S. 2011; 25 (2): E12-E14

    Abstract

    A case of postoperative fracture in the donor femur after obtaining autologous bone graft with a reamer/irrigator/aspirator is presented. This procedure was successful in healing a difficult femoral nonunion, but the patient sustained a fracture of the contralateral (bone graft donor) femur 20 days after surgery. A mechanical analysis is conducted of this case and recommendations are made. Unrestricted weightbearing on a limb that has undergone reamer/irrigator/aspirator bone graft harvesting, particularly in a noncompliant patient, is probably inadvisable. If possible, one should obtain bone graft from the same limb as the fracture being treated because this will leave the patient with one unaltered limb for mobilization.

    View details for DOI 10.1097/BOT.0b013e3181e39bf4

    View details for Web of Science ID 000286375000001

    View details for PubMedID 21245702

  • Lateral and High-Angle Oblique Radiographs of the Pelvis Aid in Diagnosing Pelvic Discontinuity After Total Hip Arthroplasty JOURNAL OF ARTHROPLASTY Giori, N. J., Sidky, A. O. 2011; 26 (1): 110-112

    Abstract

    Diagnosis of a pelvic discontinuity before revision total hip arthroplasty is critical for adequate preoperative planning. The lateral view of the pelvis or high-angle oblique views can aid in visualizing the posterior column when hip hardware obscures the view on standard anteroposterior and Judet views of the pelvis. These views are easy to obtain and can provide valuable information when planning revision total hip arthroplasty.

    View details for DOI 10.1016/j.arth.2009.12.006

    View details for Web of Science ID 000286286200018

    View details for PubMedID 20206468

  • 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

  • Bioabsorbable Tricalcium Phosphate Bone Cement Strengthens Fixation of Suture Anchors CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Oshtory, R., Lindsey, D. P., Giori, N. J., Mirza, F. M. 2010; 468 (12): 3406-3412

    Abstract

    Failure of suture anchor fixation in rotator cuff repair can occur at different interfaces. Prior studies show fixation at the bone-anchor interface can be augmented using polymethylmethacrylate (PMMA) cement, and screw fixation into bone can be strengthened using bioabsorbable tricalcium phosphate cement.We wished to determine whether augmentation of suture anchor fixation using bioabsorbable tricalcium phosphate cement would increase pullout strength of suture anchors from bone and the number of cycles to failure, to determine the mode of failure after cement augmentation, and to compare strength and mode of failure with those after augmentation with PMMA.We used 10 matched pairs of cadaveric proximal humeri and implanted a metal screw-type suture anchor in one side and on the other side injected tricalcium phosphate cement into the anchor holes before anchor placement. We tested all specimens to failure using a ramped cyclic loading protocol.Tricalcium phosphate cement augmentation increased the final load to failure by 29% and the number of cycles to failure by 20%. Visual inspection confirmed that failure occurred at the cement-bone interface.Tricalcium phosphate cement appears to augment suture anchor fixation into bone, reducing the risk of anchor pullout and failure.When relying on suture anchor fixation in bone of questionable quality, we suggest considering augmentation of suture anchor fixation with bioabsorbable cement. This method also provides potential for bioabsorbability and may be more amenable to arthroscopic application.

    View details for DOI 10.1007/s11999-010-1412-7

    View details for Web of Science ID 000288440700037

    View details for PubMedID 20521128

  • 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

  • Incidence of radiographic unicompartmental arthritis in patients undergoing knee arthroplasty. Orthopedics Woolson, S. T., Shu, B., Giori, N. J. 2010; 33 (11): 798-?

    Abstract

    Unicompartmental knee arthroplasty is increasing in popularity with the advent of less invasive procedures for knee arthritis. The percentage of patients undergoing knee arthroplasty who could be candidates for unicompartmental knee arthroplasty depends on the surgeon's evaluation of the radiographs, and this evaluation may depend on the surgeon's bias regarding partial knee arthroplasty. A retrospective radiographic and chart review was performed on a consecutive series of patients who had undergone tricompartmental knee arthroplasty to determine the percentage of those patients who could have been candidates for unicompartmental knee arthroplasty. Two hundred eighty-eight patients who underwent 308 tricompartmental knee arthroplasties over a 3-year period at a Veteran's Administration Hospital comprised the study group. Assessment of preoperative radiographs was done by 2 surgeons, 1 who favored unicompartmental knee arthroplasty and the other who preferred tricompartmental knee arthroplasty, to determine the percentage of these patients, from each surgeon's viewpoint, who had unicompartmental arthritis. Patients who had radiographic unicompartmental arthritis were then eliminated as candidates for unicompartmental knee arthroplasty, if, on chart review, they had a flexion contracture >10°, an arc of motion <100°, or inflammatory arthritis. The surgeon who was a proponent of unicompartmental knee arthroplasty found that 26% of these patients had acceptable radiologic and clinical indications for unicompartmental knee arthroplasty, whereas the surgeon who had a bias against the procedure felt that only 12% of these patients were unicompartmental knee arthroplasty candidates. A considerable percentage of Veteran's Administration patients undergoing arthroplasty for knee arthritis may be potential candidates for unicompartmental knee arthroplasty, despite the surgeon's bias for or against the procedure.

    View details for DOI 10.3928/01477447-20100924-07

    View details for PubMedID 21053889

  • Rotational References for Total Knee Arthroplasty Tibial Components Change with Level of Resection CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Graw, B. P., Harris, A. H., Tripuraneni, K. R., Giori, N. J. 2010; 468 (10): 2734-2738

    Abstract

    Various landmarks can guide tibial component rotational alignment in routine TKA, but with the deeper tibial resection levels common in complex primary and revision TKAs, it is unknown whether these landmarks remain reliable.We asked whether three techniques for determining tibial component rotation based on local anatomic landmarks are reliable deeper tibial resection levels.The femoral transepicondylar axis was identified by three independent reviewers on MR images of knees from 24 men and 24 women and transposed at a traditional tibial resection level and at the level of the proximal, middle, and distal parts of the proximal tibiofibular joint. Three axes were drawn on axial slices at these levels: the geometric center of the tibial plateau to the medial 1/3 of the tubercle, the posterior condylar line of the tibia, and the largest mediolateral dimension of the tibia. These lines were compared with the transposed femoral epicondylar axis line.The posterior condylar line of the tibia is the least variable local landmark for tibial component positioning at deep resection levels.Assuming the normal posterior condylar line of the tibia is visible at revision, setting the tibial component at 10° external rotation with respect to the posterior condylar axis of the tibia gets the tibial component within 10° of proper rotation in 86% to 98% of patients, even to the distal part of the proximal tibiofibular joint. The experienced surgeon then can adjust this position based on cues from an assortment of other axes.

    View details for DOI 10.1007/s11999-010-1330-8

    View details for Web of Science ID 000281843200024

    View details for PubMedID 20352384

  • 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

  • Unexpected finding of a fractured metal prosthetic femoral head in a nonmodular implant during revision total hip arthroplasty. journal of arthroplasty Giori, N. J. 2010; 25 (4): 659 e13-5

    Abstract

    Though there are many reports of fractured femoral components after total hip arthroplasty; there are no reports of a fractured metal femoral head. This is a report of a fractured metal femoral head in a nonmodular total hip replacement discovered unexpectedly during revision total hip arthroplasty for acetabular failure. This surprise finding, which was not appreciated on preoperative x-rays, required unplanned extraction of a well-ingrown, fully porous coated cylindrical femoral stem. Though rare, fracture of the metal femoral head in a DePuy (Warsaw, Ind.) monoblock Anatomic Medullary Locking (AML) component is possible, and one cannot expect the fracture to be apparent on preoperative radiographs as the 2 pieces may not necessarily dissociate. As usual, the surgeon performing revision arthroplasty should be prepared to revise all components.

    View details for DOI 10.1016/j.arth.2009.02.022

    View details for PubMedID 20022458

  • Single column locking plate fixation is inadequate in two column acetabular fractures. A biomechanical analysis. Journal of orthopaedic surgery and research Khajavi, K., Lee, A. T., Lindsey, D. P., Leucht, P., Bellino, M. J., Giori, N. J. 2010; 5: 30-?

    Abstract

    The objective of this study was to determine whether one can achieve stable fixation of a two column (transverse) acetabular fracture by only fixing a single column with a locking plate and unicortical locking screws. We hypothesized that a locking plate applied to the anterior column of a transverse acetabular fracture would create a construct that is more rigid than a non-locking plate, and that this construct would be biomechanically comparable to two column fixation.Using urethane foam models of the pelvis, we simulated transverse acetabular fractures and stabilized them with 1) an anterior column plate with bicortical screws, 2) an anterior locking plate with unicortical screws, 3) an anterior plate and posterior column lag screw, and 4) a posterior plate with an anterior column lag screw. These constructs were mechanically loaded on a servohydraulic material testing machine. Construct stiffness and fracture displacement were measured.We found that two column fixation is 54% stiffer than a single column fixation with a conventional plate with bicortical screws. There was no significant difference between fixation with an anterior column locking plate with unicortical screws and an anterior plate with posterior column lag screw. We detected a non-significant trend towards more stiffness for the anterior locking plate compared to the anterior non-locking plate.In conclusion, a locking plate construct of the anterior column provides less stability than a traditional both column construct with posterior plate and anterior column lag screw. However, the locking construct offers greater strength than a non-locking, bicortical construct, which in addition often requires extensive contouring and its application is oftentimes accompanied by the risk of neurovascular damage.

    View details for DOI 10.1186/1749-799X-5-30

    View details for PubMedID 20459688

  • Single column locking plate fixation is inadequate in two column acetabular fractures. A biomechanical analysis JOURNAL OF ORTHOPAEDIC SURGERY AND RESEARCH Khajavi, K., Lee, A. T., Lindsey, D. P., Leucht, P., Bellino, M. J., Giori, N. J. 2010; 5
  • 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

  • Relationship Between Dental Caries and Total Joint Arthroplasty at a Veterans Administration Hospital ORTHOPAEDIC NURSING Green-Riviere, E., Giori, N. 2009; 28 (6): 302-304

    Abstract

    It has previously been suspected that patients who undergo extensive dental procedures after having had a total joint arthroplasty (TJA) within the preceding 2 years may be at risk for seeding their TJA with infection if prophylaxis antibiotic coverage is not implemented one hour prior to the dental procedure. A review of the literature was performed to determine whether there may be other infections which may be accountable for TJA infections within the first 2 years following a TJA. Patients with systemic diseases, those who undergo extensive dental procedures, those with bladder or skin infection were found to be at risk for development of a TJA if prophylactic antibiotic therapy was not implemented in a timely manner.

    View details for Web of Science ID 000272627400005

    View details for PubMedID 20016347

  • The Proximal Hip Joint Capsule and the Zona Orbicularis Contribute to Hip Joint Stability in Distraction JOURNAL OF ORTHOPAEDIC RESEARCH Ito, H., Song, Y., Lindsey, D. P., Safran, M. R., Giori, N. J. 2009; 27 (8): 989-995

    Abstract

    The structure and function of the proximal hip joint capsule and the zona orbicularis are poorly understood. We hypothesized that the zona orbicularis is an important contributor to hip stability in distraction. In seven cadaveric hip specimens from seven male donors we distracted the femur from the acetabulum in a direction parallel to the femoral shaft with the hip in the neutral position. Eight sequential conditions were assessed: (1) intact specimen (muscle and skin removed), (2) capsule vented, (3) incised iliofemoral ligament, (4) circumferentially incised capsule, (5) partially resected capsule (distal to the zona orbicularis), (6) completely resected capsule, (7) radially incised labrum, and (8) completely resected labrum. The reduction of the distraction load was greatest between the partially resected capsule phase and completely resected capsule phase at 1, 3, and 5 mm joint distraction (p = 0.018). The proximal to middle part of the capsule, which includes the zona orbicularis, appears grossly and biomechanically to act as a locking ring wrapping around the neck of the femur and is a key structure for hip stability in distraction.

    View details for DOI 10.1002/jor.20852

    View details for Web of Science ID 000267848200002

    View details for PubMedID 19148941

  • Timing of Tourniquet Release in Total Knee Arthroplasty When Using a Postoperative Blood Salvage Drain JOURNAL OF ARTHROPLASTY Steffin, B., Green-Riviere, E., Giori, N. J. 2009; 24 (4): 539-542

    Abstract

    The purpose of this study is to examine the effect of a postoperative blood salvage drain and timing of tourniquet release on the maximal hematocrit drop after total knee arthroplasty. Thirty-seven total knees were prospectively randomized into either an early or late tourniquet release group. Hematocrit drop and drainage amounts were recorded. We found no significant difference in maximal hematocrit drop, drainage amounts, or total surgical time between the groups. We conclude that the use of a blood salvage drain should not influence the surgeon's preference on timing of tourniquet release in total knee arthroplasty.

    View details for DOI 10.1016/j.arth.2008.01.302

    View details for Web of Science ID 000266846500008

    View details for PubMedID 18534405

  • 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
  • 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
  • Meniscectomy alters the dynamic deformational behavior and cumulative strain of tibial articular cartilage in knee joints subjected to cyclic loads OSTEOARTHRITIS AND CARTILAGE Song, Y., Greve, J. M., Carter, D. R., Giori, N. J. 2008; 16 (12): 1545-1554

    Abstract

    Meniscectomy-induced osteoarthritis may be mechanically based. We asked how meniscectomy alters time-dependent deformation of physiologically loaded articular cartilage. We hypothesized that meniscectomy alters nominal strain in tibial articular cartilage, and that meniscectomy affects cartilage thickness recovery following cessation of loading.A cyclic load simulating normal gait was applied to four sheep knees. A custom device was used to obtain MR images of cartilage at 4.7T during cyclic loading. Articular cartilage thickness and nominal strain were measured every 2.5 min during 1h of cyclic loading, and during 2.5h after cessation of loading.Following meniscectomy the loaded joints rapidly developed high strain centrally and minimal strain peripherally. Maximum nominal strains after 1h of loading were about 55% in the intact knees and 72% in the meniscectomized knees. Nominal strains in the peripheral tibial cartilage were significantly reduced in the meniscectomized knees. Strain recovery was markedly prolonged in the meniscectomized knees.With meniscectomy, tibial articular cartilage in the central load bearing region remains chronically deformed and dehydrated, even after cessation of loading. Post-meniscectomy osteoarthritis may be initiated in this region by direct damage to the cartilage matrix, or by altering the hydration of the tissue. In peripheral regions, reduced loading and strain may facilitate subchondral vascular invasion, and endochondral ossification. This is consistent with the central fibrillation and peripheral osteophyte formation seen in post-meniscectomy osteoarthritis.

    View details for DOI 10.1016/j.joca.2008.04.011

    View details for Web of Science ID 000261339700015

    View details for PubMedID 18514552

  • Posterior Cruciate Ligament Removal Contributes to Abnormal Knee Motion during Posterior Stabilized Total Knee Arthroplasty JOURNAL OF ORTHOPAEDIC RESEARCH Cromie, M. J., Siston, R. A., Giori, N. J., Delp, S. L. 2008; 26 (11): 1494-1499

    Abstract

    Abnormal anterior translation of the femur on the tibia has been observed in mid flexion (20-60 degrees ) following posterior stabilized total knee arthroplasty. The underlying biomechanical causes of this abnormal motion remain unknown. The purpose of this study was to isolate the effects of posterior cruciate ligament removal on knee motion after total knee arthroplasty. We posed two questions: Does removing the posterior cruciate ligament introduce abnormal anterior femoral translation? Does implanting a posterior stabilized prosthesis change the kinematics from the cruciate deficient case? Using a navigation system, we measured passive knee kinematics of ten male osteoarthritic patients during surgery after initial exposure, after removing the anterior cruciate ligament, after removing the posterior cruciate ligament, and after implanting the prosthesis. Passively flexing and extending the knee, we calculated anterior femoral translation and the flexion angle at which femoral rollback began. Removing the posterior cruciate ligament doubled anterior translation (from 5.1 +/- 4.3 mm to 10.4 +/- 5.1 mm) and increased the flexion angle at which femoral rollback began (from 31.2 +/- 9.6 degrees to 49.3 +/- 7.3 degrees). Implanting the prosthesis increased the amount of anterior translation (to 16.1 +/- 4.4 mm), and did not change the flexion angle at which femoral rollback began. Abnormal anterior translation was observed in low and mid flexion (0-60 degrees) after removing the posterior cruciate ligament, and normal motion was not restored by the posterior stabilized prosthesis.

    View details for DOI 10.1002/jor.20664

    View details for Web of Science ID 000260195800012

    View details for PubMedID 18464260

  • Averaging Different Alignment Axes Improves Femoral Rotational Alignment in Computer-Navigated Total Knee Arthroplasty JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Siston, R. A., Cromie, M. J., Gold, G. E., Goodman, S. B., Delp, S. L., Maloney, W. J., Giori, N. J. 2008; 90A (10): 2098-2104

    Abstract

    Computer navigation systems generally establish the rotational alignment axis of the femoral component on the basis of user-defined anatomic landmarks. However, navigation systems can also record knee kinematics and average alignment axes established with multiple techniques. We hypothesized that establishing femoral rotational alignment with the use of kinematic techniques is more accurate and precise (repeatable) than the use of anatomic techniques and that establishing femoral rotational alignment by averaging the results of different alignment techniques is more accurate and precise than the use of a single technique.Twelve orthopaedic surgeons used three anatomic and two kinematic alignment techniques to establish femoral rotational alignment axes in a series of nine cadaver knees. The axes derived with the individual anatomic and kinematic techniques as well as the axes derived with six combination techniques--i.e., those involving averaging of the alignments established with two of the individual techniques--were compared against a reference axis established with computed tomography images of each femur.The kinematic methods were not more accurate (did not have smaller mean errors) or more precise (repeatable) than the anatomic techniques. The combination techniques were accurate (five of the six had a mean error of <5 degrees ) and significantly more precise than all but one of the single methods. The percentage of measurements with <5 degrees of error as compared with the reference epicondylar axis was 37% for the individual anatomic techniques, 30% for the individual kinematic techniques, and 58% for the combination techniques.Averaging the results of kinematic and anatomic techniques, which is possible with computer navigation systems, appears to improve the accuracy of rotational alignment of the femoral component. The number of rotational alignment outliers was reduced when combination techniques were used; however, they are still a problem and continued improvement in methods to accurately establish rotation of the femoral component in total knee arthroplasty is needed.

    View details for DOI 10.2106/JBJS.G.00996

    View details for Web of Science ID 000259873300006

  • 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

  • Coronal plane stability before and after total knee arthroplasty CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Siston, R. A., Goodman, S. B., Delp, S. L., Giori, N. J. 2007: 43-49

    Abstract

    The success of total knee arthroplasty depends in part on proper soft tissue management to achieve a stable joint. It is unknown to what degree total knee arthroplasty changes joint stability. We used a surgical navigation system to intraoperatively measure joint stability in 24 patients under going primary total knee arthroplasty to address two questions: (1) Is the total arc of varus-valgus motion after total knee arthroplasty different from the arc of varus-valgus motion in an osteoarthritic knee? (2) Does total knee arthroplasty produce equal amounts of varus/valgus motion (ie, is the knee "balanced")? We observed no difference between the total arc of varus-valgus motion before and after total knee arthroplasty; the total amount of motion was unchanged. On average, osteoarthritic knees were "unbalanced" but were "balanced" after prosthesis implantation. We found a negative correlation between the relative amount of varus/valgus motion in extension before and after prosthesis implantation in extension and a positive correlation between how well the knees were balanced after prosthesis implantation in extension and in flexion. Our data suggest immediately after implantation knees retain a greater than normal amount of varus-valgus motion, but this motion is more evenly distributed.

    View details for DOI 10.1097/BLO.0b013e318137a182

    View details for Web of Science ID 000250100300009

    View details for PubMedID 17621236

  • Benefit of single-leaf resection for horizontal meniscus tear CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Haemer, J. M., Wang, M. J., Carter, D. R., Giori, N. J. 2007: 194-202

    Abstract

    When treating a horizontal meniscus tear, the surgeon must decide whether to resect one or both leaves of the tear. We asked whether there is a biomechanical advantage to sparing one leaf when performing a partial meniscectomy for horizontal meniscus tear. We used pressure-sensitive film to measure the contact area, mean pressure, and peak pressure on the lateral tibial plateau of cadaveric sheep knees loaded to 2x body weight. For tears restricted to the posterior third, single-leaf resection decreased contact area by 40% compared with the intact case. Sparing one leaf was beneficial because resection of the second leaf reduced contact area an additional 15%. Similarly, mean pressure was increased 24% for single-leaf resection and an additional 27% for double-leaf resection. Peak pressure showed no differences with single- and double-leaf resections. For tears that span the entire meniscus, single-leaf resection reduced contact area by 59%, increased mean pressure by 55%, and increased peak pressure by 19%. Double-leaf resection in this situation did not change these values substantially, suggesting sparing one leaf offers no benefit over resecting both leaves with extensive horizontal meniscus tears.

    View details for DOI 10.1097/BLO.0b0I13e3180303b5c

    View details for Web of Science ID 000245575600030

    View details for PubMedID 17179782

  • Two ulnar collateral ligament reconstruction methods: The docking technique versus bioabsorbable interference screw fixation - A biomechanical evaluation with cyclic loading JOURNAL OF SHOULDER AND ELBOW SURGERY McAdams, T. R., Lee, A. T., Centeno, J., Giori, N. J., Lindsey, D. P. 2007; 16 (2): 224-228

    Abstract

    We compared the effects of cyclic valgus loading on 2 techniques for reconstruction of the elbow ulnar collateral ligament (UCL): the docking procedure and the bioabsorbable interference screw procedure. A cyclic valgus load was applied to the 16 unembalmed elbows, and the valgus angle was measured at 1, 10, 100, and 1000 cycles. Testing was repeated after UCL palmaris tendon reconstruction via either the docking technique or bioabsorbable interference screw fixation. At cycle 1, the valgus angle was not different between treated and intact cases. At cycles 10 and 100, the valgus angle for the docking technique was significantly greater than that for both the intact cases and the interference screw technique. By the 1000th cycle, no difference was measured between the 2 techniques. In this study, bioabsorbable interference screw fixation resulted in less valgus angle widening in response to early cyclic valgus load as compared with the docking technique.

    View details for DOI 10.1016/j.jse.2005.12.012

    View details for Web of Science ID 000245426200016

    View details for PubMedID 17254812

  • Surgical navigation for total knee arthroplasty: A perspective JOURNAL OF BIOMECHANICS Siston, R. A., Giori, N. J., Goodman, S. B., Delp, S. L. 2007; 40 (4): 728-735

    Abstract

    A new generation of surgical tools, known as surgical navigation systems, has been developed to help surgeons install implants more accurately and reproducibly. Navigation systems also record quantitative information such as joint range of motion, laxity, and kinematics intra-operatively. This article reviews the history of surgical navigation for total knee arthroplasty, the biomechanical principles associated with this technology, and the related clinical research studies. We describe how navigation has the potential to address three main challenges for total knee arthroplasty: ensuring excellent and consistent outcomes, treating younger and more physically active patients, and enabling less invasive surgery.

    View details for DOI 10.1016/j.jbiomech.2007.01.006

    View details for Web of Science ID 000245111200003

    View details for PubMedID 17317419

  • The high variability of tibial rotational alignment in total knee arthroplasty CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Siston, R. A., Goodman, S. B., Patel, J. J., Delp, S. L., Giori, N. J. 2006: 65-69

    Abstract

    Although various techniques are advocated to establish tibial rotational alignment during total knee arthroplasty, it is unknown which is most repeatable. We evaluated the precision and accuracy of five tibial rotational alignment techniques to determine whether computer-assisted navigation systems can reduce variability of tibial component rotational alignment when compared to traditional instrumentation. Eleven orthopaedic surgeons used four computer-assisted techniques that required identification of anatomical landmarks and one that used traditional extramedullary instrumentation to establish tibial rotational alignment axes on 10 cadaver legs. Two computer-assisted techniques (axes between the most medial and lateral border of the tibial plateau, and between the posterior cruciate ligament [PCL] and the anterior tibial crest) and the traditional technique were least variable, with standard deviations of 9.9 degrees, 10.8 degrees, and 12.1 degrees, respectively. Computer-assisted techniques referencing the tibial tubercle (axes between the PCL and the medial border or medial 1/3 of the tubercle) were most variable, with standard deviations of 27.4 degrees and 28.1 degrees. The axis between the medial border of the tibial tubercle and the PCL was internally rotated compared to the other techniques. None of the techniques consistently established tibial rotational alignment, and navigation systems that establish rotational alignment by identifying anatomic landmarks were not more reliable than traditional instrumentation.

    View details for DOI 10.1097/01.blo.0000229335.36900.a0

    View details for Web of Science ID 000243021400013

    View details for PubMedID 16906095

  • Bone cement improves suture anchor fixation CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Giori, N. J., Sohn, D. H., Mirza, F. M., Lindsey, D. P., Lee, A. T. 2006: 236-241

    Abstract

    Suture anchor fixation failure can occur if the anchor pulls out of bone. We hypothesized that suture anchor fixation can be augmented with polymethylmethacrylate cement, and that polymethylmethacrylate can be used to improve fixation in a stripped anchor hole. Six matched cadaveric proximal humeri were used. On one side, suture anchors were placed and loaded to failure using a ramped cyclic loading protocol. The stripped anchor holes then were injected with approximately 1 cc polymethylmethacrylate, and anchors were replaced and tested again. In the contralateral humerus, polymethylmethacrylate was injected into anchor holes before anchor placement and testing. In unstripped anchors, polymethylmethacrylate increased the number of cycles to failure by 34% and failure load by 71% compared with anchors not augmented with polymethylmethacrylate. Polymethylmethacrylate haugmentation of stripped anchors increased the cycles to failure by 31% and failure load by 111% compared with unstripped uncemented anchors. No difference was found in cycles to failure or failure load between cemented stripped anchors and cemented unstripped anchors. Polymethylmethacrylate can be used to augment fixation, reducing the risk of anchor pull-out failure, regardless whether the suture anchor hole is stripped or unstripped.

    View details for DOI 10.1097/01.blo.0000223984.67325.af

    View details for Web of Science ID 000243021200043

    View details for PubMedID 16702922

  • Gene regulation ex vivo within a wrap-around tendon TISSUE ENGINEERING Li, K. W., Lindsey, D. P., Wagner, D. R., Giori, N. J., Schurman, D. J., Goodman, S. B., Smith, R. L., Carter, D. R., Beaupre, G. S. 2006; 12 (9): 2611-2618

    Abstract

    This study tested the hypothesis that physiologic tendon loading modulates the fibrous connective tissue phenotype in undifferentiated skeletal cells. Type I collagen sponges containing human bone marrow stromal cells (MSCs) were implanted into the midsubstance of excised sheep patellar tendons. An ex vivo loading system was designed to cyclically stretch each tendon from 0 to 5% at 1.0 Hz. The MSC-sponge constructs were implanted into 2 tendon sites: the first site subjected to tension only and a second site located at an artificially created wrap-around region in which an additional compressive stress was generated transverse to the longitudinal axis of the tendon. The induced contact pressure at the wraparound site was 0.55 +/- 0.12 MPa, as quantified by pressure-sensitive film. An MSC-sponge construct was maintained free swelling in the same bath as an unloaded control. After 2 h of tendon stretching, the MSC-sponge constructs were harvested and real-time PCR was used to quantify Fos, Sox9, Cbfa1 (Runx2), and scleraxis mRNA expression as markers of skeletal differentiation. Two hours of mechanical loading distinctly altered MSC differentiation in the wrap-around region and the tensile-only region, as evidenced by differences in Fos and Sox9 mRNA expression. Expression of Fos mRNA was 13 and 52 times higher in the tensile-only and wrap-around regions, respectively, compared to the free-swelling controls. Expression of Sox9 mRNA was significantly higher (2.5-3 times) in MSCs from the wraparound region compared to those from the tensile-only region or in free-swelling controls. In contrast, expression levels for Cbfa1 did not differ among constructs. Scleraxis mRNA was not detected in any construct. This study demonstrates that the physiologic mechanical environment in the wrap-around regions of tendons provides stimuli for upregulating early response genes and transcription factors associated with chondrogenic differentiation. These differentiation responses begin within as little as 2 h after the onset of mechanical stimulation and may be the basis for the formation of fibrocartilage that is typically found in the wrap-around region of mature tendons in vivo.

    View details for Web of Science ID 000240780900021

    View details for PubMedID 16995794

  • Articular cartilage MR imaging and thickness mapping of a loaded knee joint before and after meniscectomy OSTEOARTHRITIS AND CARTILAGE Song, Y., Greve, J. M., Carter, D. R., Koo, S., Giori, N. J. 2006; 14 (8): 728-737

    Abstract

    We describe a technique to axially compress a sheep knee joint in an MRI scanner and measure articular cartilage deformation. As an initial application, tibial articular cartilage deformation patterns after 2 h of static loading before and after medial meniscectomy are compared.Precision was established for repeated scans and repeated segmentations. Accuracy was established by comparing to micro-CT measurements. Four sheep knees were then imaged unloaded, and while statically loaded for 2 h at 1.5 times body weight before and after medial meniscectomy. Images were obtained using a 3D gradient echo sequence in a 4.7 T MRI. Corresponding 3D cartilage thickness models were created. Nominal strain patterns for the intact and meniscectomized conditions were compared.Coefficients of variation were all 2% or less. Root mean squared errors of MR cartilage thickness measurements averaged less than 0.09 mm. Meniscectomy resulted in a 60% decrease in the contact area (P=0.001) and a 13% increase in maximum cartilage deformation (P=0.01). Following meniscectomy, there were greater areas of articular cartilage experiencing abnormally high and low nominal strains. Areas of moderate nominal strain were reduced.Medial meniscectomy resulted in increased medial tibial cartilage nominal strains centrally and decreased strains peripherally. Areas of abnormally high nominal strain following meniscectomy correlated with areas that are known to develop fibrillation and softening 16 weeks after medial meniscectomy. Areas of abnormally low nominal strain correlated with areas of osteophyte formation. Studies of articular cartilage deformation may prove useful in elucidating the mechanical etiology of osteoarthritis.

    View details for DOI 10.1016/j.joca.2006.01.011

    View details for Web of Science ID 000239386900002

    View details for PubMedID 16533610

  • Intraoperative passive kinematics of osteoarthritic knees before and after total knee arthroplasty JOURNAL OF ORTHOPAEDIC RESEARCH Siston, R. A., Giori, N. J., Goodman, S. B., Delp, S. L. 2006; 24 (8): 1607-1614

    Abstract

    Total knee arthroplasty is a successful procedure to treat pain and functional disability due to osteoarthritis. However, precisely how a total knee arthroplasty changes the kinematics of an osteoarthritic knee is unknown. We used a surgical navigation system to measure normal passive kinematics from 7 embalmed cadaver lower extremities and in vivo intraoperative passive kinematics on 17 patients undergoing primary total knee arthroplasty to address two questions: How do the kinematics of knees with advanced osteoarthritis differ from normal knees?; and, Does posterior substituting total knee arthroplasty restore kinematics towards normal? Osteoarthritic knees displayed a decreased screw-home motion and abnormal varus/valgus rotations between 10 degrees and 90 degrees of knee flexion when compared to normal knees. The anterior-posterior motion of the femur in osteoarthritic knees was not different than in normal knees. Following total knee arthroplasty, we found abnormal varus/valgus rotations in early flexion, a reduced screw-home motion when compared to the osteoarthritic knees, and an abnormal anterior translation of the femur during the first 60 degrees of flexion. Posterior substituting total knee arthroplasty does not appear to restore normal passive varus/valgus rotations or the screw motion and introduces an abnormal anterior translation of the femur during intraoperative evaluation.

    View details for DOI 10.1002/jor.20163

    View details for Web of Science ID 000239364300004

    View details for PubMedID 16770795

  • Prepolarized magnetic resonance imaging around metal orthopedic implants MAGNETIC RESONANCE IN MEDICINE Venook, R. D., Matter, N. I., Ramachandran, M., Ungersma, S. E., Gold, G. E., Giori, N. J., Macovski, A., Scott, G. C., Conolly, S. M. 2006; 56 (1): 177-186

    Abstract

    A prepolarized MRI (PMRI) scanner was used to image near metal implants in agar gel phantoms and in in vivo human wrists. Comparison images were made on 1.5- and 0.5-T conventional whole-body systems. The PMRI experiments were performed in a smaller bore system tailored to extremity imaging with a prepolarization magnetic field of 0.4 T and a readout magnetic field of 27-54 mT (1.1-2.2 MHz). Scan parameters were chosen with equal readout gradient strength over a given field of view and matrix size to allow unbiased evaluation of the benefits of lower readout frequency. Results exhibit substantial reduction in metal susceptibility artifacts under PMRI versus conventional scanners. A new artifact quantification technique is also presented, and phantom results confirm that susceptibility artifacts improve as expected with decreasing readout magnetic field using PMRI. This proof-of-concept study demonstrates that prepolarized techniques have the potential to provide diagnostic cross-sectional images for postoperative evaluation of patients with metal implants.

    View details for DOI 10.1002/mrm.20927

    View details for Web of Science ID 000238823600019

    View details for PubMedID 16724303

  • Evaluation of methods that locate the center of the ankle for computer-assisted total knee arthroplasty CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Siston, R. A., Daub, A. C., Giori, N. J., Goodman, S. B., Delp, S. L. 2005: 129-135

    Abstract

    Accurate alignment of the mechanical axis of the limb is important to the success of a total knee arthroplasty. Although computer-assisted navigation systems can align implants more accurately than traditional mechanical guides, the ideal technique to determine the distal end point of the mechanical axis, the center of the ankle, is unknown. In this study, we evaluated the accuracy, precision, objectivity, and speed of five anatomic methods and two kinematic methods for estimating the ankle center in 11 healthy subjects. Magnetic resonance images were used to characterize the shape of the ankle and establish the true ankle center. The most accurate and precise anatomic method was establishing the midpoint of the most medial and most lateral aspects of the malleoli (4.5 +/- 4.1 mm lateral error; 2.7 +/- 4.5 mm posterior error). A biaxial model of the ankle (2.0 +/- 6.4 mm medial error; 0.3 +/- 7.6 mm anterior error) was the most accurate kinematic method. Establishing the midpoint of the most medial and most lateral aspects of the malleoli was an accurate, precise, objective, and fast method for establishing the center of the ankle.

    View details for DOI 10.1097/01.blo.0000170873.88306.56

    View details for Web of Science ID 000232457700027

    View details for PubMedID 16205151

  • The variability of femoral rotational alignment in total knee arthroplasty JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Siston, R. A., Patel, J. J., Goodman, S. B., Delp, S. L., Giori, N. J. 2005; 87A (10): 2276-2280

    Abstract

    Several reference axes are used to establish femoral rotational alignment during total knee arthroplasty, but debate continues with regard to which axis is most accurately and easily identified during surgery. Computer-assisted navigation systems have been developed in an attempt to more accurately and consistently align implants during total knee arthroplasty, but it is unknown if navigation systems can improve the accuracy of femoral rotational alignment as compared with that achieved with more traditional techniques involving mechanical guides. The purposes of the present study were to characterize the variability associated with femoral rotational alignment techniques and to determine whether the use of a computer-assisted surgical navigation system reduced this variability.Eleven orthopaedic surgeons used five alignment techniques (including one computer-assisted technique and four traditional techniques) to establish femoral rotational alignment axes on ten cadaveric specimens, and the orientation of these axes was recorded with use of a navigation system. These derived axes were compared against a reference transepicondylar axis on each femur that was established after complete dissection of all soft tissues.There was no difference between the mean errors of all five techniques (p > 0.11). Only 17% of the knees were rotated <5 degrees from the reference transepicondylar axis, with alignment errors ranging from 13 degrees of internal rotation to 16 degrees of external rotation. There were significant differences among the surgeons with regard to their ability to accurately establish femoral rotational alignment axes (p < 0.001).All techniques resulted in highly variable rotational alignment, with no technique being superior. This variability was primarily due to the particular surgeon who was performing the alignment procedure. A navigation system that relies on directly digitizing the femoral epicondyles to establish an alignment axis did not provide a more reliable means of establishing femoral rotational alignment than traditional techniques did.

    View details for DOI 10.2106/JBJS.D.02945

    View details for Web of Science ID 000232421500018

  • Load-shifting brace treatment for osteoarthritis of the knee: A minimum 2 1/2-year follow-up study JOURNAL OF REHABILITATION RESEARCH AND DEVELOPMENT Giori, N. J. 2004; 41 (2): 187-193

    Abstract

    Objectives in treating primarily unicompartmental knee arthritis with a load-shifting brace are pain relief, compliance, brace durability, and complication-free treatment over multiple years. This was a single institution retrospective chart review, radiograph review, and telephone survey of patients treated from 1997 to 1999 with a load-shifting knee brace. Forty-six patients (49 knees) with a minimum 2 1/2-year follow-up (average 3.3 years) were reviewed. Kaplan-Meier survivorship analysis revealed that load-shifting brace use had a survival of 76% at 1 year, 69% at 2 years, and 61% at 3 years. Younger patients had a higher likelihood of longer brace use than older patients. One patient had ipsilateral leg swelling and a pulmonary embolus after initiating bracing. Eliminating the high numbers of early failures would be desirable. One should be aware of the potential complication of venous thrombosis and thromboembolism.

    View details for Web of Science ID 000221807600011

    View details for PubMedID 15558372

  • Acetabular retroversion is associated with osteoarthritis of the hip CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Giori, N. J., Trousdale, R. T. 2003: 263-269

    Abstract

    Primary osteoarthritis of the hip may have a structural basis. It was hypothesized that the radiographic appearance of acetabular retroversion could be created by altering the morphologic features of the acetabular walls, and that acetabular retroversion, as defined on an anteroposterior radiograph of the pelvis, is associated with osteoarthritis of the hip. A model pelvis was used to simulate normal, augmented, deficient, and rotated walls of the acetabulum, and radiographs were taken to compare the projections of the modified acetabular walls with the known plain radiographic appearance of a retroverted acetabulum. One hundred thirty-one good quality anteroposterior radiographs of the pelvis taken before total hip arthroplasty for idiopathic hip osteoarthritis were compared with 99 good quality radiographs taken for nonorthopaedic reasons. The prevalence of radiographic acetabular retroversion is 20% among patients with idiopathic hip osteoarthritis and 5% among the general population. The appearance of acetabular retroversion on an anteoroposterior radiograph of the pelvis is created by deficiency of the posterior wall of the acetabulum. There is a statistically significant association between radiographic acetabular retroversion and hip osteoarthritis. These findings have applicability to understanding the mechanical etiology of hip osteoarthritis, and to surgical technique during periacetabular osteotomy and total hip arthroplasty.

    View details for DOI 10.1097/01.blo.0000093014.90435.64

    View details for Web of Science ID 000188760900030

    View details for PubMedID 14646725

  • Offset acetabular components introduce torsion on the implant and may increase the risk of fixation failure JOURNAL OF ARTHROPLASTY Giori, N. J. 2003; 18 (1): 89-91

    Abstract

    Loading of an offset acetabular component causes torsion on the implant around the center of the reamed acetabular bed. A mechanical analysis was performed to determine this torsional moment. A 70 kg person walking normally on a well-positioned, 4-mm offset acetabular component will produce torsion on the prosthesis of approximately 3.86 Nm. A 10-mm offset increases the applied torsion to 9.65 Nm. Vertical placement of the cup further increases this torsion. These torsional moments are comparable to moments shown to cause failure of the initial interference fit of cementless acetabular components in vitro. If using an offset cementless acetabular component, one should initially limit weight bearing and consider using pegs or screws to augment fixation and minimize the risk of interference fit failure.

    View details for DOI 10.1054/arth.2003.50018

    View details for Web of Science ID 000180808600016

    View details for PubMedID 12555189

  • Total knee arthroplasty in limbs affected by poliomyelitis. journal of bone and joint surgery. American volume Giori, N. J., Lewallen, D. G. 2002; 84-A (7): 1157-1161

    Abstract

    Little information is available regarding the results and complications of total knee arthroplasty in limbs affected by poliomyelitis with severe knee degeneration.We performed a retrospective chart and radiograph review of patients with a history of poliomyelitis involving a limb that subsequently underwent primary total knee arthroplasty between 1970 and 2000. Sixteen total knee arthroplasties were performed in limbs affected by poliomyelitis in fifteen patients. Eleven patients were followed for a minimum of two years, one (two knees) died before the minimum two-year follow-up could be completed, and three were followed for less than two years. No patient was lost to follow-up.There were two periprosthetic fractures, one peroneal nerve palsy, one avulsion of the patellar tendon, and four cases of recurrent instability. These complications were related to the poor bone quality, valgus deformity, patella baja, poor musculature, and attenuated soft tissues commonly found in knees affected by poliomyelitis. Knee Society pain and knee scores were improved postoperatively for all nine knees with a two-year follow-up that had had at least antigravity quadriceps strength prior to surgery. However, Knee Society function scores remained at 0 or worsened for six of the eleven knees followed for at least two years, including those with less than antigravity strength, and four of the nine knees with at least antigravity strength. None of the prostheses loosened.Pain and knee scores improved following total knee arthroplasty in patients with a history of poliomyelitis and antigravity quadriceps strength, but there was less pain relief in patients with less than antigravity quadriceps strength. Recurrence of instability and progressive functional deterioration is possible in all knees affected by poliomyelitis that have undergone total knee replacement, but they appear to occur more commonly in more severely affected knees.

    View details for PubMedID 12107315

  • Measurement of perioperative flexion-extension mechanics of the knee joint JOURNAL OF ARTHROPLASTY Giori, N. J., Giori, K. L., Woolson, S. T., Goodman, S. B., Lannin, J. V., Schurman, D. J. 2001; 16 (7): 877-881

    Abstract

    Perioperative knee mechanics currently are evaluated Perioperative knee mechanics currently are evaluated by measuring range of motion. This is an incomplete measurement, however, because the torque applied to achieve the motion is not measured. We hypothesized that a custom goniometer and force transducer could measure the torque required to passively flex a knee through its full range of motion. This measurement was done in the operating room immediately before and after surgery in 20 knees having total knee arthroplasty and 9 having surgery on another limb. Surgery changed the mechanics of 8 knees, whereas unoperated knees remained unchanged. This measurement technique is safe, easy, and repeatable. It improves on the current standard of perioperative knee measurement and can be applied to investigate the effects of surgery and rehabilitation on ultimate knee motion.

    View details for Web of Science ID 000171577100010

    View details for PubMedID 11607904

  • Continuous passive motion (CPM): Theory and principles of clinical application JOURNAL OF REHABILITATION RESEARCH AND DEVELOPMENT O'Driscoll, S. W., Giori, N. J. 2000; 37 (2): 179-188

    Abstract

    Stiffness following surgery or injury to a joint develops as a progression of four stages: bleeding, edema, granulation tissue, and fibrosis. Continuous passive motion (CPM) properly applied during the first two stages of stiffness acts to pump blood and edema fluid away from the joint and periarticular tissues. This allows maintenance of normal periarticular soft tissue compliance. CPM is thus effective in preventing the development of stiffness if full motion is applied immediately following surgery and continued until swelling that limits the full motion of the joint no longer develops. This concept has been applied successfully to elbow rehabilitation, and explains the controversy surrounding CPM following knee arthroplasty. The application of this concept to clinical practice requires a paradigm shift, resulting in our attention being focused on preventing the initial or delayed accumulation of periarticular interstitial fluids.

    View details for Web of Science ID 000165733400011

    View details for PubMedID 10850824

  • Coincident development of sesamoid bones and clues to their evolution ANATOMICAL RECORD Sarin, V. K., Erickson, G. M., Giori, N. J., Bergman, A. G., Carter, D. R. 1999; 257 (5): 174-180

    Abstract

    Sesamoid bones form within tendons in regions that wrap around bony prominences. They are common in humans but variable in number. Sesamoid development is mediated epigenetically by local mechanical forces associated with skeletal geometry, posture, and muscular activity. In this article we review the literature on sesamoids and explore the question of genetic control of sesamoid development. Examination of radiographs of 112 people demonstrated that the relatively infrequent appearances of the fabella (in the lateral gastrocnemius tendon of the knee) and os peroneum (in the peroneus longus tendon of the foot) are related within individuals (P < 0.01). This finding suggests that the tendency to form sesamoids may be linked to intrinsic genetic factors. Evolutionary character analyses suggest that the formation of these sesamoids in humans may be a consequence of phylogeny. These observations indicate that variations of intrinsic factors may interact with extrinsic mechanobiological factors to influence sesamoid development and evolution.

    View details for Web of Science ID 000083555500005

    View details for PubMedID 10597342

  • Mechanobiology of skeletal regeneration CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Carter, D. R., Beaupre, G. S., Giori, N. J., Helms, J. A. 1998: S41-S55

    Abstract

    Skeletal regeneration is accomplished by a cascade of biologic processes that may include differentiation of pluripotential tissue, endochondral ossification, and bone remodeling. It has been shown that all these processes are influenced strongly by the local tissue mechanical loading history. This article reviews some of the mechanobiologic principles that are thought to guide the differentiation of mesenchymal tissue into bone, cartilage, or fibrous tissue during the initial phase of regeneration. Cyclic motion and the associated shear stresses cause cell proliferation and the production of a large callus in the early phases of fracture healing. For intermittently imposed loading in the regenerating tissue: (1) direct intramembranous bone formation is permitted in areas of low stress and strain; (2) low to moderate magnitudes of tensile strain and hydrostatic tensile stress may stimulate intramembranous ossification; (3) poor vascularity can promote chondrogenesis in an otherwise osteogenic environment; (4) hydrostatic compressive stress is a stimulus for chondrogenesis; (5) high tensile strain is a stimulus for the net production of fibrous tissue; and (6) tensile strain with a superimposed hydrostatic compressive stress will stimulate the development of fibrocartilage. Finite element models are used to show that the patterns of tissue differentiation observed in fracture healing and distraction osteogenesis can be predicted from these fundamental mechanobiologic concepts. In areas of cartilage formation, subsequent endochondral ossification normally will proceed, but it can be inhibited by intermittent hydrostatic compressive stress and accelerated by octahedral shear stress (or strain). Later, bone remodeling at these sites can be expected to follow the same mechanobiologic adaptation rules as normal bone.

    View details for Web of Science ID 000077173200007

    View details for PubMedID 9917625

  • Stress governs tissue phenotype at the femoral insertion of the rabbit MCL. Journal of biomechanics Giori, N. J., Beaupré, G. S., Carter, D. R. 1996; 29 (4): 573-574

    View details for PubMedID 8964789

  • MECHANICAL INFLUENCES ON TISSUE DIFFERENTIATION AT BONE-CEMENT INTERFACES JOURNAL OF ARTHROPLASTY Giori, N. J., Ryd, L., Carter, D. R. 1995; 10 (4): 514-522

    Abstract

    Retrieval studies have shown that tissue at the bone-cement or bone-implant interface can develop into fibrous tissue, fibrocartilage, and bone, and that tissue differentiation appears to be mechanically influenced. A prior histologic analysis of retrieved interface tissues supporting cemented Marmor unicondylar knee components found that beneath the central portion of these implants, a thick, mature layer of fibrocartilage consistently developed, whereas fibrous tissue formed beneath the prosthesis periphery and adjacent to the bone beneath the tibial spine. Finite-element analysis was used to model the interface tissue supporting a cemented Marmor tibial component and interpreted patterns of stress and strain generated in the interface according to a mechanically based tissue differentiation theory. Distortional strain and hydrostatic stress, mechanical stimuli that are hypothesized to be associated with fibrous matrix and cartilaginous matrix production, respectively, were found to correlate well with the previous histologic findings. Given the biologic environments in which the retrieved interface tissues developed, frequently applied hydrostatic stress of approximately 0.7 MPa may be sufficient to stimulate cartilaginous extracellular matrix production in the interface tissue, and frequently applied distortional strain of 10% may be sufficient to stimulate fibrous extracellular matrix production.

    View details for Web of Science ID A1995RT19900017

    View details for PubMedID 8523012

  • CELLULAR-SHAPE AND PRESSURE MAY MEDIATE MECHANICAL CONTROL OF TISSUE COMPOSITION IN TENDONS JOURNAL OF ORTHOPAEDIC RESEARCH Giori, N. J., Beaupre, G. S., Carter, D. R. 1993; 11 (4): 581-591

    Abstract

    In vivo studies have suggested that mechanical factors are involved in the regulation of the morphology and biochemical composition of tendons that wrap around bones. In these tendons, fibrocartilage is found in the segment wrapped around the bone, and tendon far from the bone displays normal tendon histomorphology. Recent in vitro studies have shown that intermittently loaded connective tissue cells are sensitive to changes in cellular shape and hydrostatic pressure: stretching and distortion of the cells enhances production of fibrous matrix and hydrostatic pressure enhances production of cartilaginous matrix. We used finite-element analysis to determine whether the regions of increased development of cartilaginous matrix in tendons that wrap around bones correspond to regions in which tendon cells are subjected to higher pressures, and whether the maintenance and rearrangement of fibrous extracellular matrix in these tendons is associated with regions of stretching and distortion of cells. We found that regions of cartilaginous matrix and fibrous matrix formation and turnover correlate well with patterns of hydrostatic compressive stress and distortional strain in the tendon. Although further experiments clearly are needed to establish the predictive value of our approach, hydrostatic stress and distortional strain history--parameters intimately related to changes in cellular pressure and shape, respectively--appear to be important tissue-level mechanical stimuli that regulate cartilaginous and fibrous matrix composition of connective tissues.

    View details for Web of Science ID A1993LQ68800012

    View details for PubMedID 8340830

  • A comparison of unicortical and bicortical end screw attachment of fracture fixation plates. Journal of orthopaedic trauma Beaupré, G. S., Giori, N. J., CALER, W. E., CSONGRADI, J. 1992; 6 (3): 294-300

    Abstract

    Plate fixation is considered by many clinicians to be the treatment of choice for displaced diaphyseal fractures of the forearm. One possible complication associated with plate fixation is refracture with the plate in situ or after plate removal. With the plate in situ, refracture typically occurs through the last screw hole near the end of the plate. Some clinicians have advocated the use of unicortical end screws to minimize the risk of such refractures. In this study, we performed a series of in vitro tests to compare the breaking strength of plated bone analogues that used either unicortical or bicortical end screws. The plated constructs that used unicortical end screws were significantly weaker in the two most important physiologic loading modes. Based on these results, we conclude that the use of unicortical end screws may result in a greater risk of refracture with the plate in situ.

    View details for PubMedID 1403247

  • THE INFLUENCE OF FIXATION PEG DESIGN ON THE SHEAR STABILITY OF PROSTHETIC IMPLANTS JOURNAL OF ORTHOPAEDIC RESEARCH Giori, N. J., Beaupre, G. S., Carter, D. R. 1990; 8 (6): 892-898

    Abstract

    The variety of fixation peg designs existing on prosthetic implants indicates uncertainty regarding the optimum design of fixation pegs for the reduction of stress and relative motion at the bone-implant interface. Fixation pegs have a number of important functions on a prosthesis, one of which is to reduce shear stress and shear displacement at the bone-implant interface. This is a parametric study intended to identify trends in the shear stability of prostheses incorporating a range of fixation peg designs. The parameters varied included the number of fixation pegs on a surface, the size of the pegs, and the aspect ratio (length/diameter) of the pegs. Mechanical tests were performed on urethane foam blocks with mechanical properties comparable to trabecular bone. The results indicated the following: (a) Fixation pegs act independently in resisting shearing force if they are spaced sufficiently far apart. (b) For any given shear displacement, smaller pegs generate a greater resistive shear force per unit of peg projected area in the direction of the applied load than larger pegs having the same aspect ratio. (c) Smaller diameter pegs cause the supporting material to yield at lower displacements. (d) Pegs with a high aspect ratio provide high shear stability with a minimum amount of bone removed, but may bend if the aspect ratio becomes excessive. (e) Smaller, slender pegs generate a greater resistive shear force at a given displacement per unit of peg volume than larger, lower aspect ratio pegs.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1990EF13000014

    View details for PubMedID 2213346

Conference Proceedings


  • Acetabular Component Positioning Using the Transverse Acetabular Ligament Can You Find It and Does It Help? Epstein, N. J., Woolson, S. T., Giori, N. J. SPRINGER. 2011: 412-416

    Abstract

    Several studies have reported that the transverse acetabular ligament (TAL) can be used to orient the acetabular component during total hip arthroplasty and that it can be identified in nearly all patients.We attempted to determine how often the TAL could be identified during primary THA and its accuracy as a guide for acetabular component positioning.In a prospective series of 63 patients (64 hips) undergoing primary THA, two surgeons attempted to identify the TAL and, if it was found, to use it for acetabular component orientation. Patients in whom the TAL was identified served as the study group and the ligament was used for cup orientation in those patients; the remaining patients in whom the ligament could not be identified served as a control group and had free-hand cup positioning. Anteversion was determined by radiographic measurement from true lateral views.The TAL was identified in only 30 hips (47%) and was more likely to be found in patients who did not have inferior acetabular osteophytes. Acetabular position was not improved using this ligament for reference.The TAL could not be routinely identified at surgery and when used for cup orientation it was no more accurate for cup positioning than free-hand technique.

    View details for DOI 10.1007/s11999-010-1523-1

    View details for Web of Science ID 000286939300013

    View details for PubMedID 20737303

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