Bio

Clinical Focus


  • Neurological Surgery
  • Spine Deformity Surgery
  • Spine Trauma
  • Minimally Invasive Spine surgery
  • Spine Tumor Surgery
  • Cyberknife Spine Tumor

Academic Appointments


Administrative Appointments


  • Chief, Spine Neurosurgery, Stanford UMC. (2006 - Present)
  • Director, Comprehensive Spine Neurosurgery Program. Spine Fellowship and Spine Research Program, Stanford UMC. (2006 - Present)
  • Associate Professor, Stanford Univ. School of Medicine, Department of Neurosurgery (2010 - Present)
  • Assistant Professor, Stanford Univ. School of Medicine, Department of Neurosurgery (2003 - 2009)
  • Assistant Professor, University of Washington School of Medicine, Neurological Surgery (2000 - 2003)
  • Clinical Instructor, UCLA School of Medicine, Neurological Surgery (1999 - 2000)

Honors & Awards


  • Health Commendation Award, City of Baltimore (1986)
  • HANA Graduate Merit Scholarship, Johns Hopkins University (1990)
  • Robert I. Weed Hematology Research Fellowship, Johns Hopkins University (1991)
  • Kathleen Whipple Scholarship, University of Rochester School of Medicine (1990-1993)
  • President of Fellow's Society, Montreal Neurological Institute, Montreal Neurological Institute (1998-1999)
  • Stanford University School of Medicine Academic Grant Recipient, Stanford (2003-2004)

Professional Education


  • Residency:University of Washington Medical Center (1995) WA
  • Board Certification: Neurological Surgery, American Board of Neurological Surgery (2005)
  • Fellowship:UCLA - School of Medicine (2000) CA
  • Spine Fellowship, UCLA Medical Center, Neurological Surgery (2000)
  • Chief Resident, McGill University, Neurosurgery, Neurological Surgery (1999)
  • Residency:Montreal Neurological Institute (1999) QCCanada
  • Fellowship, Lahey Hitchcock Medical Center, Interventional Neuroradiology (1997)
  • Intern & Resident, University of Washington, General Surgery (1995)
  • Medical Education:University of Rochester-Highland Hospital (1993) NY
  • B.A., Johns Hopkins University, Biophysics (1989)

Research & Scholarship

Current Research and Scholarly Interests


Non-fusion dynamic spinal stabilization, artificial disc technologies, and regenerative spinal technologies.

Teaching

2013-14 Courses


Graduate and Fellowship Programs


Publications

Journal Articles


  • Radiofrequency Ablation of Spine An Experimental Study in an Ex Vivo Bovine and In Vivo Swine Model for Feasibility in Spine Tumor SPINE You, N. K., Lee, H. Y., Shin, D. A., Choi, G. H., Yi, S., Kim, K. N., Yoon, D. H., Park, J. 2013; 38 (18): E1121-E1127

    Abstract

    Study Design. An experimental study of radiofrequency ablation of spine in an ex vivo bovine and in vivo swine animal model.Objective. To study the feasibility of radiofrequency ablation for spine tumors close to the spinal cord, to examine the safety and efficacy of radiofrequency ablation, and to suggest quantitative guidelines for clinical application.Summary of Background Data. Radiofrequency ablation has received increased attention as an effective and minimally invasive method for treating soft tissue tumors. However, there is currently only anecdotal evidence to support radiofrequency ablation of spinal tumors and only a few experimental studies have been conducted.Methods. We performed ex vivo experiments by producing 10 radiofrequency ablation zones in extracted bovine spines and an in vivo study by producing eight radiofrequency ablation zones in a swine spine using internally cooled electrodes. The volume and diameter of ablation zones were evaluated and analyzed by the corresponding energy and ablation times.Results. In the ex vivo study, the average diameters of the ablation zones were 3.05 cm, 1.85 cm, and 1.26 cm, for the D1, D2, and D3 zones, respectively, and the average ablation volume was 4.19 cm. In the in vivo study, the average diameters were 2.51 cm, 2.05 cm, and 1.28 cm, respectively, and the ablation volume was 6.80 cm. The ablation zones demonstrated a positive correlation with ablation time, but the coefficients were 0.942 ex vivo and 0.257 in vivo. The temperature in the ex vivo study was inversely proportional to distance, with a maximal temperature of 63.7°C at 10 mm; however, the maximum temperature was 38.2°C in the in vivo study.Conclusion. This study demonstrated that sufficient radiofrequency ablation zone volume could be induced, which suggests that radiofrequency ablation is feasible and safe for application to human spinal tumors with predictability.

    View details for DOI 10.1097/BRS.0b013e31829c2e12

    View details for Web of Science ID 000330365000001

    View details for PubMedID 23698575

  • Modified Polyaxial S1 Screw Placement in Patients with Difficult Sacral Anatomy - Technical Report Cureus 5(1): e83. doi:10.7759/cureus.83 M Kalani, G Li, S Mindea, J Park 2013
  • The Design of a Heterocellular 3D Architecture and its Application to Monitoring the Behavior of Cancer Cells in Response to the Spatial Distribution of Endothelial Cells ADVANCED MATERIALS Lee, W., Park, J. 2012; 24 (39): 5339-5344

    Abstract

    The spatial cell distribution is one of the critical features for governing cellular interactions and their consequent behaviors. Here we suggest a novel method of building a hierarchical cellular structure by stacking cell-attached microplate structures with specific configurations within hydrogel layers. This method is applied to the reconstruction of the 3D architecture of a liver lobule and the development of an experimental model of the various phases of cancer angiogenesis.

    View details for DOI 10.1002/adma.201200687

    View details for Web of Science ID 000309405200006

    View details for PubMedID 22927197

  • Morbidity and Mortality of C2 Fractures in the Elderly: Surgery and Conservative Treatment NEUROSURGERY Chen, Y., Boakye, M., Arrigo, R. T., Kalanithi, P. S., Cheng, I., Alamin, T., Carragee, E. J., Mindea, S. A., Park, J. 2012; 70 (5): 1055-1059

    Abstract

    Closed C2 fractures commonly occur after falls or other trauma in the elderly and are associated with significant morbidity and mortality. Controversy exists as to best treatment practices for these patients.To compare outcomes for elderly patients with closed C2 fractures by treatment modality.We retrospectively reviewed 28 surgically and 28 nonsurgically treated cases of closed C2 fractures without spinal cord injury in patients aged 65 years of age or older treated at Stanford Hospital between January 2000 and July 2010. Comorbidities, fracture characteristics, and treatment details were recorded; primary outcomes were 30-day mortality and complication rates; secondary outcomes were length of hospital stay and long-term survival.Surgically treated patients tended to have more severe fractures with larger displacement. Charlson comorbidity scores were similar in both groups. Thirty-day mortality was 3.6% in the surgical group and 7.1% in the nonsurgical group, and the 30-day complication rates were 17.9% and 25.0%, respectively; these differences were not statistically significant. Surgical patients had significantly longer lengths of hospital stay than nonsurgical patients (11.8 days vs 4.4 days). Long-term median survival was not significantly different between groups.The 30-day mortality and complication rates in surgically and nonsurgically treated patients were comparable. Elderly patients faced relatively high morbidity and mortality regardless of treatment modality; thus, age alone does not appear to be a contraindication to surgical fixation of C2 fractures.

    View details for DOI 10.1227/NEU.0b013e3182446742

    View details for Web of Science ID 000303390400013

    View details for PubMedID 22157549

  • Charlson Score is a Robust Predictor of 30-Day Complications Following Spinal Metastasis Surgery SPINE Arrigo, R. T., Kalanithi, P., Cheng, I., Alamin, T., Carragee, E. J., Mindea, S. A., Boakye, M., Park, J. 2011; 36 (19): E1274-E1280

    Abstract

    Retrospective chart review.To identify predictors of 30-day complications after the surgical treatment of spinal metastasis.Surgical treatment of spinal metastasis is considered palliative with the aim of reducing or delaying neurologic deficit. Postoperative complication rates as high as 39% have been reported in the literature. Complications may impact patient quality of life and increase costs; therefore, an understanding of which preoperative variables best predict 30-day complications will help risk-stratify patients and guide therapeutic decision making and informed consent.We retrospectively reviewed 200 cases of spinal metastasis surgically treated at Stanford Hospital between 1999 and 2009. Multiple logistic regression was performed to determine which preoperative variables were independent predictors of 30-day complications.Sixty-eight patients (34%) experienced one or more complications within 30 days of surgery. The most common complications were respiratory failure, venous thromboembolism, and pneumonia. On multivariate analysis, Charlson Comorbidity Index score was the most significant predictor of 30-day complications. Patients with a Charlson score of two or greater had over five times the odds of a 30-day complication as patients with a score of zero or one.After adjusting for demographic, oncologic, neurologic, operative, and health factors, Charlson score was the most robust predictor of 30-day complications. A Charlson score of two or greater should be considered a surgical risk factor for 30-day complications, and should be used to risk-stratify surgical candidates. If complications are anticipated, medical staff can prepare in advance, for instance, scheduling aggressive ICU care to monitor for and treat complications. Finally, Charlson score should be controlled for in future spinal metastasis outcomes studies and compared to other comorbidity assessment tools.

    View details for DOI 10.1097/BRS.0b013e318206cda3

    View details for Web of Science ID 000294207500005

    View details for PubMedID 21358481

  • Biomechanical analysis of Goel technique for C1-2 fusion JOURNAL OF NEUROSURGERY-SPINE Park, J., Scheer, J. K., Lim, T. J., Deviren, V., Ames, C. P. 2011; 14 (5): 639-646

    Abstract

    The Goel technique, in which C1-2 intraarticular spacers are used, may be performed to restore stability to a disrupted atlantoaxial complex in conjunction with the Harms technique of placing polyaxial screws and bilateral rods. However, it has yet to be determined biomechanically whether the addition of the C1-2 joint spacers increases the multiaxial rigidity of the fixation construct. The goal of this study was to quantify changes in multiaxial rigidity of the combined Goel-Harms technique with the addition of C1-2 intraarticular spacers.Seven cadaveric cervical spines (occiput-C2) were submitted to nondestructive flexion-extension, lateral bending, and axial rotation tests in a material testing machine spine tester. The authors applied 1.5 Nm at a rate of 0.1 Nm/second and held it constant for 10 seconds. The specimens were loaded 3 times, and data were collected on the third cycle. Testing of the specimens was performed for the following groups: 1) intact (I); 2) with the addition of C-1 lateral mass/C-2 pedicle screws and rod system (I+SR); 3) with C1-2 joint capsule incision, decortication (2 mm on top and bottom of each joint [that is, the C-1 and C-2 surface) and addition of bilateral C1-2 intraarticular spacers at C1-2 junction to the screws and rods (I+SR+C); 4) after removal of the posterior rods and only the bilateral spacers in place (I+C); 5) after removal of spacers and further destabilization with simulated odontoidectomy for a completely destabilized case (D); 6) with addition of posterior rods to the destabilized case (D+SR); and 7) with addition of bilateral C1-2 intraarticular spacers at C1-2 junction to the destabilized case (D+SR+C). The motion of C-1 was measured by a 3D motion tracking system and the motion of C-2 was measured by the rotational sensor of the testing system. The range of motion (ROM) and neutral zone (NZ) across C-1 and C-2 were evaluated.For the intact spine test groups, the addition of screws/rods (I+SR) and screws/rods/cages (I+SR+C) significantly reduced ROM and NZ compared with the intact spine (I) for flexion-extension and axial rotation (p < 0.05) but not lateral bending (p > 0.05). The 2 groups were not significantly different from each other in any bending mode for ROM and NZ, but in the destabilized condition the addition of screws/rods (D+SR) and screws/rods/cages (D+SR+C) significantly reduced ROM and NZ compared with the destabilized spine (D) in all bending modes (p < 0.05). Furthermore, the addition of the C1-2 intraarticular spacers (D+SR+C) significantly reduced ROM (flexion-extension and axial rotation) and NZ (lateral bending) compared with the screws and rods alone (D+SR).Study result indicated that both the Goel and Harms techniques alone and with the addition of the C1-2 intraarticular spacers to the Goel-Harms technique are advantageous for stabilizing the atlantoaxial segment. The Goel technique combined with placement of a screw/rod construct appears to result in additional construct rigidity beyond the screw/rod technique and appears to be more useful in very unstable cases.

    View details for DOI 10.3171/2011.1.SPINE10446

    View details for Web of Science ID 000289914100014

    View details for PubMedID 21332283

  • Biomechanical Evaluations of Various C1-C2 Posterior Fixation Techniques SPINE Sim, H. B., Lee, J. W., Park, J. T., Mindea, S. A., Lim, J., Park, J. 2011; 36 (6): E401-E407

    Abstract

    A biomechanical in vitro study using human cadaveric spine.To compare the biomechanical stability of pedicle screws versus various established posterior atlantoaxial fixations used to manage atlantoaxial instability.Rigid screw fixation of the atlantoaxial complex provides immediate stability and excellent fusion success though has a high risk of neurovascular complications. Some spine surgeons thus insert shorter C2 pedicle or pars/isthmus screws as alternatives to minimize the latter risks. The biomechanical consequences of short pedicle screw fixation remain unclear, however.Seven human cadaveric cervical spines with the occiput attached (C0-C3) had neutral zone (NZ) and range of motion (ROM) evaluated in three modes of loading. Specimens were tested in the following sequence: initially (1) the intact specimens were tested, after destabilization of C1-C2, then the specimens underwent (2) C1 lateral mass and C2 short pedicle screw fixation (PS-S), (3) C1 lateral mass and C2 long pedicle screw fixation (PS-L), (4) C1 lateral mass and C2 intralaminar screw fixation (ILS), (5) Sonntag's modified Gallie fixation (MG) and (6) C1-C2 transarticular screw fixation with posterior wiring (TAS 1 MG). (7) The destabilized spine was also tested.All instrumented groups were significantly stiffer in NZ and ROM than the intact spines, except in lateral bending, which was statistically significantly increased in the TAS 1 MG group. The MG group's NZ and ROM values were statistically significantly weaker than those of the PS-S, PS-L, and the ROM values of the TAS 1 MG groups. The ILS group's NZ values were higher than those of the TAS 1 MG group and for ROM, than that of the PS-S and PS-L groups. In flexion, the NZ and ROM values of the TAS 1 MG group were significantly less than those of the PS-S, PS-L, ILS, and MG groups. In axial rotation, the NZ and ROM values of the MG group were statistically significantly higher than those of the PS-S, PS-L, ISL and TAS 1 MG groups.The TAS 1 MG procedures provided the highest stability. The MG method alone may not be adequate for atlantoaxial arthrodesis, because it does not provide sufficient stability in lateral bending and rotation modes. The C2 pedicle screw and C2 ILS techniques are biomechanically less stable than the TAS 1 MG. In the C1 lateral mass-C2 pedicle screw fixation, the use of a short pedicle screw may be an alternative when other screw fixation techniques are not feasible.

    View details for DOI 10.1097/BRS.0b013e31820611ba

    View details for Web of Science ID 000288005700005

    View details for PubMedID 21372651

  • Open Posterior Reduction and Stabilization of a C1 Burst Fracture Using Mono-axial Screws SPINE Chung, S. K., Park, J. T., Lim, J., Park, J. 2011; 36 (5): E301-E306

    View details for DOI 10.1097/BRS.0b013e31820644cd

    View details for Web of Science ID 000287446300002

    View details for PubMedID 21325928

  • Predictors of Survival After Surgical Treatment of Spinal Metastasis NEUROSURGERY Arrigo, R. T., Kalanithi, P., Cheng, I., Alamin, T., Carragee, E. J., Mindea, S. A., Park, J., Boakye, M. 2011; 68 (3): 674-681

    Abstract

    Surgery for spinal metastasis is a palliative treatment aimed at improving patient quality of life by alleviating pain and reversing or delaying neurologic dysfunction, but with a mean survival time of less than 1 year and significant complication rates, appropriate patient selection is crucial.To identify the most significant prognostic variables of survival after surgery for spinal metastasis.Chart review was performed on 200 surgically treated spinal metastasis patients at Stanford Hospital between 1999 and 2009. Survival analysis was performed and variables entered into a Cox proportional hazards model to determine their significance.Median overall survival was 8.0 months, with a 30-day mortality rate of 3.0% and a 30-day complication rate of 34.0%. A Cox proportional hazards model showed radiosensitivity of the tumor (hazard ratio: 2.557, P<.001), preoperative ambulatory status (hazard ratio: 2.355, P=.0001), and Charlson Comorbidity Index (hazard ratio: 2.955, P<.01) to be significant predictors of survival. Breast cancer had the best prognosis (median survival, 27.1 months), whereas gastrointestinal tumors had the worst (median survival, 2.66 months).We identified the Charlson Comorbidity Index score as one of the strongest predictors of survival after surgery for spinal metastasis. We confirmed previous findings that radiosensitivity of the tumor and ambulatory status are significant predictors of survival.

    View details for DOI 10.1227/NEU.0b013e318207780c

    View details for Web of Science ID 000287242300036

    View details for PubMedID 21311295

  • Lumbar disc rehydration postimplantation of a posterior dynamic stabilization system JOURNAL OF NEUROSURGERY-SPINE Cho, B. Y., Murovic, J., Park, K. W., Park, J. 2010; 13 (5): 576-580

    Abstract

    Biological attempts at disc regeneration are promising; however, disc degeneration is closely related to other predisposing factors such as alteration of disc height, intradiscal pressure, load distribution, and motion. The restoration of the physiological status of the affected spinal segment is thus necessary prior to attempts at disc regeneration. Dynamic stabilization systems now offer the potential of a mechanical approach to intervertebral disc regeneration. The authors used decompression and placement of the BioFlex dynamic stabilization device to treat a young male patient with disc degeneration. This patient underwent follow-up, and he was found to gradually improve both neurologically and radiographically. On MR imaging performed 1 year postoperatively, he had an increase in disc height and disc rehydration. This case and the concept of disc rehydration are presented in this paper.

    View details for DOI 10.3171/2010.5.SPINE08418

    View details for Web of Science ID 000283473600005

    View details for PubMedID 21039146

  • Biomechanical Analysis of the Range of Motion After Placement of a Two-Level Cervical ProDisc-C Versus Hybrid Construct SPINE Cho, B. Y., Lim, J., Sim, H. B., Park, J. 2010; 35 (19): 1769-1776

    Abstract

    The study design was that of an in vitro human cadaveric biomechanical analysis.The objective of this study was the biomechanical analysis of the range of motion (ROM) of a 2-level intact spine control versus total, then operative- and adjacent-segment ROM after (1) 2-level ProDisc-C placement (PP), (2) anterior cervical discectomy and fusions (ACDFs), and (3) hybrid constructs of both. Follower load and multidirectional testing were performed in each instance.With in vivo cervical arthroplasties gaining in popularity, limited biomechanical data are available, which highlight changes in the adjacent-level biomechanics after multilevel procedures.Biomechanical testing for ROM was performed using 7 cadaveric C4-T1 spine specimens. Moments up to 2 Nm with a 100 N follower load were applied in flexion/extension (F/E), right and left lateral bending (LB), and right and left axial rotation (AR). Specimens were tested in the intact state and then with a combination of ProDisc-C arthroplasty and ACDF at C5-C6 and C6-C7.In the 2-level PP group, the increase in ROM in F/E, LB, and AR of C4-T1 occurs due to an increased ROM at the operative level. The ROM of the level adjacent to the operative levels showed no significant change, except at C4-C5 in LB. For the latter level, the ROM of C4-C5 in each direction showed increases for each parameter. In the 2-level fusion C5-C6 and C6-C7 fusion (FF) group, the ROM in F/E, LB, and AR of C4-T1 was decreased because of a decrease in ROM primarily at the fused levels, and the ROM of adjacent levels was increased. In the ProDisc-C/Fusion (PF) and Fusion/ProDisc-C (FP) groups undergoing placements of a 1-level ProDisc-C/1-level fusion with cage and plate, both groups showed no significant ROM change of C4-T1 when compared with the control and no significant change at adjacent levels, with the exception of C4-C5 in LB.(1) Two-level ACDFs decrease whereas 2-level PPs increase the entire C4-T1 ROM. (2) ACDF/ProDisc-C hybrid operations do not alter the C4-T1 ROM. (3) For the ACDF/ProDisc-C hybrid operative groups, the combined ROM of the operative levels showed no significant difference when compared with that of the intact spine. (4) Regarding adjacent-level ROM, a 2-level ACDF increases ROM, but 2-level ProDisc-C and hybrid ACDF/PPs do not show significant change except for LB at C4-C5. (5) When the segmental distribution of C4-T1 ROM is plotted as the percentage of total motion, it demonstrates that for PF and FP groups, the combined ROM of the C5-C6 and C6-C7 operative levels are similar to that of the intact spine in EF and LB. For the PP group, the combined ROM of the operative levels increased, whereas the combined ROM for the FF group is decreased. The decrease or increase of the adjacent C4-C5 or C7-T1 level ROM compensates for the operative levels.

    View details for DOI 10.1097/BRS.0b013e3181c225fa

    View details for Web of Science ID 000281656400005

    View details for PubMedID 20395885

  • Biomechanical comparison of single-level posterior versus transforaminal lumbar interbody fusions with bilateral pedicle screw fixation: segmental stability and the effects on adjacent motion segments Laboratory investigation JOURNAL OF NEUROSURGERY-SPINE Sim, H. B., Murovic, J. A., Cho, B. Y., Lim, T. J., Park, J. 2010; 12 (6): 700-708

    Abstract

    Both posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) have been frequently undertaken for lumbar arthrodesis. These procedures use different approaches and cage designs, each of which could affect spine stability, even after the addition of posterior pedicle screw fixation. The objectives of this biomechanical study were to compare PLIF and TLIF, each accompanied by bilateral pedicle screw fixation, with regard to the stability of the fused and adjacent segments.Fourteen human L2-S2 cadaveric spine specimens were tested for 6 different modes of motion: flexion, extension, right and left lateral bending, and right and left axial rotation using a load control protocol (LCP). The LCP for each mode of motion utilized moments up to 8.0 Nm at a rate of 0.5 Nm/second with the application of a constant compression follower preload of 400 N. All 14 specimens were tested in the intact state. The specimens were then divided equally into PLIF and TLIF conditions. In the PLIF Group, a bilateral L4-5 partial facetectomy was followed by discectomy and a single-level fusion procedure. In the TLIF Group, a unilateral L4-5 complete facetectomy was performed (and followed by the discectomy and single-level fusion procedure). In the TLIF Group, the implants were initially positioned inside the disc space posteriorly (TLIF-P) and the specimens were tested; the implants were then positioned anteriorly (TLIF-A) and the specimens were retested. All specimens were evaluated at the reconstructed and adjacent segments for range of motion (ROM) and at the adjacent segments for intradiscal pressure (IDP), and laminar strain.At the reconstructed segment, both the PLIF and the TLIF specimens had significantly lower ROMs compared with those for the intact state (p < 0.05). For lateral bending, the PLIF resulted in a marked decrease in ROM that was statistically significantly greater than that found after TLIF (p < 0.05). In flexion-extension and rotation, the PLIF Group also had less ROM, however, unlike the difference in lateral bending ROM, these differences in ROM values were not statistically significant. Variations in the position of the implants within the disc space were not associated with any significant differences in ROM values (p = 0.43). Analyses of ROM at the adjacent levels L2-3, L3-4, and L5-S1 showed that ROM was increased to some degree in all directions. When compared with that of intact specimens, the ROMs were increased to a statistically significant degree at all adjacent segments in flexion-extension loads (p < 0.05); however, the differences in values among the various operative procedures were not statistically significant. The IDP and facet contact force for the adjacent L3-4 and L5-S1 levels were also increased, but these values were not statistically significantly increased from those for the intact spine (p > 0.05).Regarding stability, PLIF provides a higher immediate stability compared with that of TLIF, especially in lateral bending. Based on our findings, however, PLIF and TLIF, each with posterolateral fusions, have similar biomechanical properties regarding ROM, IDP, and laminar strain at the adjacent segments.

    View details for DOI 10.3171/2009.12.SPINE09123

    View details for Web of Science ID 000278024300017

    View details for PubMedID 20515358

  • A biomechanical study of the instrumented and adjacent lumbar levels after In-Space interspinous spacer insertion Laboratory investigation JOURNAL OF NEUROSURGERY-SPINE Park, S. W., Lim, T. J., Park, J. 2010; 12 (5): 560-569

    Abstract

    Interspinous process implants are becoming more common for the treatment of lumber disc degeneration. The authors undertook this study to evaluate the effect of the In-Space interspinous spacer on the biomechanics of the lumbosacral spine.Seven L2-S1 cadaver spines were physiologically loaded in extension, flexion, lateral bending, and axial rotation modes. The range of motion (ROM) and intervertebral disc pressure (DP) at the level implanted with an In-Space device and at adjacent levels were measured under 4 experimental conditions. Biomechanical testing was carried out on 7 sequentially prepared specimens in the following states: 1) the intact L2-S1 cadaver spine and 2) the L2-S1 cadaver specimen implanted with an In-Space interspinous spacer at L3-4 (Group 1), 3) after an additional L3-4 discectomy (with the In-Space interspinous spacer still in place) (Group 2), and finally, 4) after removal of the In-Space interspinous spacer, leaving only the discectomized (that is, destabilized) spine model (Group 3).The extension ROM at the implanted level after experimental conditions 2 and 3 above was statistically significantly reduced. An increase of ROM at the adjacent levels compensated for the reduction at the implanted level. However, there was no statistically significant change in ROM in any of the other modes of motion at any of the levels studied. Likewise, the DP reduction at L3-4 during extension was statistically significant, but in all other modes of motion, there was no statistically significant change in DP at any measured level. The In-Space interspinous spacer statistically significantly reduced the ROM of the L3-4 motion segment in Groups 1 and 2 (extension: 67%, p = 0.018 and 70%, p = 0.018; flexion: 72%, p = 0.028 and 80%, p = 0.027). After placement of the In-Space interspinous spacer, the DP was decreased at L3-4 in extension for Groups 1 and 2 in the posterior anular region (63%, p = 0.028; 59%, p = 0.043), Group 2 in the center region (73%, p = 0.028), and Groups 1 and 2 in the anterior anular region (57%, p = 0.018; 60%, p = 0.018).The In-Space interspinous spacer both stabilizes the spine and reduces the intervertebral DP at the instrumented level during extension. The biomechanics for other modes of motion and at the adjacent levels are not affected statistically significantly, however. The device thus performed as intended. It significantly stabilized the motion segments at the instrumented level, but not at the segment adjacent to the instrumented level.

    View details for DOI 10.3171/2009.11.SPINE08668

    View details for Web of Science ID 000277132000017

    View details for PubMedID 20433305

  • DRIVING WITH POLYNEUROPATHY MUSCLE & NERVE Cho, S. C., Katzberg, H. D., Rama, A., Kim, B., Roh, H., Park, J., Katz, J., So, Y. T. 2010; 41 (3): 324-328

    Abstract

    Polyneuropathy may result in pain, numbness, and weakness, which may in turn affect driving ability. Medications used to treat neuropathic pain may alter cognition, which may further affect driving. Although such impairments have engendered questions about the driving safety in this group of patients, the rate of motor vehicle accidents (MVAs) in patients with neuropathy has not been studied rigorously. We surveyed patients with neuropathy from three medical centers for reported accident rate, and we analyzed variables related to increased risk for accidents compared to National Highway Traffic Safety Administration data. Surveys from 260 subjects demonstrated that 40.6% were involved in traffic accidents (0.11 accidents/year). Their accident rate was 10.8 MVAs per million vehicle miles traveled (MVA/MVMT), compared to 3.71 MVA/MVMT in 55-59-year-old drivers and 3.72 in 60-64-year-olds (National Highway Traffic Safety Administration data). In all, 72.4% cited their neuropathy and 55.2% cited their medications as playing a role in their accidents, and 51.6% changed their driving habits after developing neuropathy. Independently, elevated levels of pain, motor weakness, and ambulation difficulty met statistical significance for increased MVA frequency. We conclude that accident frequency and discomfort with driving are higher in neuropathy patients compared to age-matched national statistics. However, most patients seem to change habits according to their ability to drive; as such, driving issues should be addressed with caution and on a case-by-case basis.

    View details for DOI 10.1002/mus.21511

    View details for Web of Science ID 000275139700005

    View details for PubMedID 19882633

  • Surgical strategies for managing foraminal nerve sheath tumors: the emerging role of CyberKnife ablation EUROPEAN SPINE JOURNAL Murovic, J. A., Cho, S. C., Park, J. 2010; 19 (2): 242-256

    Abstract

    Sixteen Stanford University Medical Center (SUMC) patients with foraminal nerve sheath tumors had charts reviewed. CyberKnife radiosurgery was innovative in management. Parameters were evaluated for 16 foraminal nerve sheath tumors undergoing surgery, some with CyberKnife. Three neurofibromas had associated neurofibromatosis type 1 (NF1). Eleven patients had one resection; others had CyberKnife after one (two) and two (three) operations. The malignant peripheral nerve sheath tumor (MPNST) had prior field-radiation and adds another case. Approaches included laminotomy and laminectomies with partial (three) or total (two) facetectomies/fusions. Two cases each had supraclavicular, lateral extracavitary, retroperitoneal and Wiltze and costotransversectomy/thoracotomy procedures. Two underwent a laminectomy/partial facetectomy, then CyberKnife. Pre-CyberKnife, one of two others had a laminectomy/partial facetectomy, then total facetectomy/fusion and the other, two supraclavicular approaches. The MPNST had a hemi-laminotomy then laminectomy/total facetectomy/fusion, followed by CyberKnife. Roots were preserved, except in two. Of 11 single-operation-peripheral nerve sheath tumors, the asymptomatic case remained stable, nine (92%) improved and one (9%) worsened. Examinations remained intact in three (27%) and improved in seven (64%). Two having a single operation then CyberKnife had improvement after both. Of two undergoing two operations, one had symptom resolution post-operatively, worsened 4 years post-CyberKnife then has remained unchanged after re-operation. The other such patient improved post-operatively, had no change after re-operation and improved post-CyberKnife. The MPNST had presentation improvement after the first operation, worsened and after the second surgery \and CyberKnife, the patient expired from tumor spread. In conclusion, surgery is beneficial for pain relief and function preservation in foraminal nerve sheath tumors. Open surgery with CyberKnife is an innovation in these tumors' management.

    View details for DOI 10.1007/s00586-009-1160-0

    View details for Web of Science ID 000274545200006

    View details for PubMedID 19798517

  • "Mini-transthoracic supradiaphragmatic approach to the thoracolumbar junction" Korean J Spine Chang JC, Park HK, Doh JW, Park J 2010; 7 (4): 249-254
  • Fracture-related Thoracic Kyphotic Deformity Correction by Single-stage Posterolateral Vertebrectomy With Circumferential Reconstruction and Stabilization Outcomes in 30 Cases JOURNAL OF SPINAL DISORDERS & TECHNIQUES Yoo, C., Ryu, S. I., Park, J. 2009; 22 (7): 492-501

    Abstract

    This paper is a retrospective chart review.This study assesses single-stage thoracic vertebrectomy with circumferential reconstruction and stabilization. Preoperative and postoperative thoracic kyphotic angles and other outcomes are analyzed.Pathologic and traumatic thoracic vertebral body fracture deformity can be corrected by an anterior vertebral body corpectomy and reconstruction. If the pathology is primarily posterior, then laminectomy and posterolateral instrumentation may be preferred. In some patients, simultaneous anterior and posterior correction of instability and fracture is necessary and is now possible with a single-stage Stanford University Medical Center (SUMC) technique with similar results to the traditional 2-stage approach.Thirty patients who underwent 31 single-stage thoracic vertebrectomies with circumferential reconstructions for thoracic spine fractures between 2004 and 2006 at SUMC were retrospectively reviewed. All surgeries were performed prone; operative technical details are reported. The preoperative and postoperative thoracic kyphotic angles were measured by Cobb angle evaluation using lateral chest plain films and magnetic resonance imaging. Other outcome measures evaluated included operative time, blood loss, neurologic and functional outcomes, postoperative pain, and treatment complications.The mean follow-up was 17.21 months (range: 9 to 30 mo) and preoperative kyphosis was 20.4 degrees (range: 6.0 to 57.9 degrees). The average postoperative kyphosis was 8.3 degrees (range: 1.8 to 2.67 degrees) and correction of kyphosis was 16.2 degrees (range: 6 to 30 degrees). The median estimated blood loss was 1411.67 mL (range: 300 to 4000 mL) and mean operating time was 4.8 hours (range: 2.8 to 8.6 h). Complications included 2 hardware failures requiring revision, 2 infections, and 1 dural laceration. Pain, Frankel Grade, and functional status were improved in all, except 1 preoperatively bedridden patient.Thoracic kyphotic correction is possible through a prone single-stage simultaneous anterior vertebrectomy and posterior reconstruction. Sufficient anterior and posterior correction of instability and fracture using the SUMC technique is possible with similar results to the traditional 2-stage approach.

    View details for DOI 10.1097/BSD.0b013e31818f0ec3

    View details for Web of Science ID 000279665400006

    View details for PubMedID 20075812

  • FORAMINAL NERVE SHEATH TUMORS: INTERMEDIATE FOLLOW-UP AFTER CYBERKNIFE RADIOSURGERY NEUROSURGERY Murovic, J. A., Gibbs, I. C., Chang, S. D., Mobley, B. C., Park, J., Adler, J. R. 2009; 64 (2): A33-A43

    Abstract

    To conduct a retrospective review of outcomes in 15 patients with 18 foraminal tumors, including 17 benign peripheral nerve sheath tumors and 1 malignant peripheral nerve sheath tumor, who underwent CyberKnife (Accuray, Inc., Sunnyvale, CA) radiosurgery at Stanford University Medical Center from 1999 to 2006.Symptoms and findings, neurofibromatosis (NF) association, previous radiation, imaging, dosimetry, tumor volume, central necrosis, and the relation of these factors to outcomes were evaluated.Before treatment, 1 asymptomatic patient had radiculopathic findings, 3 patients experienced local pain with intact neurological examinations, and 7 patients had radiculopathic complaints with intact (1 patient), radiculopathic (4 patients), or radiculomyelopathic examinations (2 patients). Five patients had myelopathic complaints and findings. Three patients had NF1-associated neurofibromas, 1 patient with NF2 had a schwannoma, and 1 patient had a schwannomatosis-related lesion. Two likely radiation-induced lesions, a neurofibroma and a malignant peripheral nerve sheath tumor, were observed. Prescribed doses ranging from 16 to 24 Gy, delivered in 1 to 3 fractions of 6 to 20 Gy, resulted in maximum tumor doses ranging from 20.9 to 30 Gy. Target volumes ranged from 1.36 to 16.9 mL. After radiosurgery, the asymptomatic case remained asymptomatic, and neurological findings improved. Thirteen of 15 symptomatic patients with (12 patients) or without (3 patients) neurological findings improved (3 cases after resection) or remained stable, and 2 patients worsened. Symptoms and examinations remained stable or improved in 8 (80%) of 10 patients with schwannomas and 3 (60%) of 5 patients with neurofibromas. Tumor volumes decreased in 12 (67%) of 18 tumors and increased in 3 tumors. Tumor volumes decreased in 8 of 10 schwannomas and 3 of 7 neurofibromas. Central necrosis developed in 8 (44%) of 18 tumors.CyberKnife radiosurgery resulted in pain relief and functional preservation in selected foraminal peripheral nerve sheath tumors and a malignant peripheral nerve sheath tumor. Symptomatic and neurological improvements were more noticeable with schwannomas. Myelopathic symptoms may necessitate surgical debulking before radiosurgery.

    View details for DOI 10.1227/01.NEU.0000341632.39692.9E

    View details for Web of Science ID 000262797700010

    View details for PubMedID 19165072

  • Imaging Correlation of the Degree of Degenerative L4-L5 Spondylolisthesis with the Corresponding Amount of the Facet Fluid. Journal of Neurosurgery: Spine Cho BY, Park J 2009; 11: 614-619
  • Stem Cell Regeneration of the Intervertebral Disc-Cellular and Molecular Challenges Neurosurgery Focus Jandial R, Aryan HE, Park J, Taylor WT, Snyder EY 2008; 24 (E:20)
  • Requests for 692 transfers to an academic Level I trauma center: Implications of the Emergency Medical Treatment and Active Labor Act JOURNAL OF TRAUMA-INJURY INFECTION AND CRITICAL CARE Spain, D. A., Bellino, M., Kopelman, A., Chang, J., Park, J., Gregg, D. L., Brundage, S. I. 2007; 62 (1): 63-67

    Abstract

    The Emergency Medical Treatment and Active Labor Act (EMTALA) effectively requires Level I trauma centers (TC) to accept all transfers for a higher level of care if capacity exists. We hypothesized that EMTALA would burden a Level I TC by a selective referral of a poor payer mix of primarily nonoperative patients.All transfer calls (December 2003 and September 2005) to our Level I TC are handled by a dedicated transfer center. Calls were reviewed for age, surgical service requested, and outcome of request. The trauma registry was queried to compare Injury Severity Scale (ISS) score, hospital stay (LOS), operations, mortality, and payer status for transfer and primary catchment patients.In all, 821 calls were received; 77 calls were cancelled by the referring hospital and 52 were for consultation only. Of the 692 transfer requests, 534 (77%) were accepted, 134 (19%) were denied for no capacity, and only 24 (4%) were declined by TC as not clinically indicated. Transferred patients were younger (32.0 +/- 1.49 versus 38.9 +/- 0.51, p < 0.05), had similar ISS scores (13.6 +/- 0.62 versus 13.7 +/- 0.26) and LOS (7.0 +/- 0.70 versus 7.4 +/- 0.25), but were somewhat more likely to require an operation than direct admissions (58% versus 51%, p < 0.05). Although trauma (24%) and neurosurgery (24%) were the most commonly requested services, followed by orthopedics (20%), orthopedics accounted for 60% of operations on transferred patients compared with 10% to 13% for trauma and neurosurgery (mostly spine). There was no difference in the payer status of transfer and direct admit patients.Contrary to our assumptions, EMTALA patients had an identical payer mix and similar operative need compared with our primary catchment patients. They do represent a large additional patient load (20% of admissions) and differentially impact specialists, mostly operative for orthopedics and complex nonoperative care for trauma and neurosurgery. These data suggest that the primary motivations for transfer are specialist availability and complexity of care rather than financial concerns. As TCs provide backup specialty call coverage for a wide geographic area, this further supports the need for trauma systems development.

    View details for DOI 10.1097/TA.0b013e31802d9716

    View details for Web of Science ID 000243490100012

    View details for PubMedID 17215734

  • Treatment of Fracture-Related Thoracic Kyphosis by Circumferential Reconstruction and Stabilization via a Prone Extracavitary Costotransversectomy Approach The Spine Journal Yoo C, Ryu C, Park J 2007; 7 (Supplement): 120S-121S
  • Posterior Dynamic Stabilization Systems Korean Journal of Spine Park SW, Park J 2007; 4 (4): 171-187
  • The Effect of a Posterior Dynamic Stabilization Device on Extension Using Finite Element Analysis Korean Journal of Spine Min SW, Park J 2007; 4 (Suppl. 1): 58-59
  • Expandable Cage for Cervical Spine Reconstruction J Korean Neurosurgery Ho Yeol Zhang, Thongtrangan I, Le H, Park J, Kim, DH 2005; Soc 38: 435-441
  • Biomechanical comparison: stability of lateral-approach anterior lumbar interbody fusion and lateral fixation compared with anterior-approach anterior lumbar interbody fusion and posterior fixation in the lower lumbar spine JOURNAL OF NEUROSURGERY-SPINE Kim, S. M., Lim, T. J., Paterno, J., Park, J., Kim, D. H. 2005; 2 (1): 62-68

    Abstract

    The stability of lateral lumbar interbody graft-augmented fusion and supplementary lateral plate fixation in human cadavers has not been determined. The purpose of this study was to investigate the immediate biomechanical stabilities of the following: 1) femoral ring allograft (FRA)-augmented anterior lumbar interbody fusion (ALIF) after left lateral discectomy combined with additional lateral MACS HMA plate and screw fixation; and 2) ALIF combined with posterior transpedicular fixation after anterior discectomy.Sixteen human lumbosacral spines were loaded with six modes of motion. The intervertebral motion was measured using a video-based motion-capturing system. The range of motion (ROM) and the neutral zone (NZ) in each loading mode were compared with a maximum of 7.5 Nm. The ROM values for both stand-alone ALIF approaches were similar to those of the intact spine, whereas NZ measurements were higher in most loading modes. No significant intergroup differences were found. The ROM and NZ values for lateral fixation in all modes were significantly lower than those of intact spine, except when NZ was measured in lateral bending. All ROM and NZ values for transpedicular fixation were significantly lower than those for stand-alone anterior ALIF. Transpedicular fixation conferred better stabilization than lateral fixation in flexion, extension, and lateral bending modes.Neither approach to stand-alone FRA-augmented ALIF provided sufficient stabilization, but supplementary instrumentation conferred significant stabilization. The MACS HMA plate and screw fixation system, although inferior to posterior transpedicular fixation, provided adequate stability compared with the intact spine and can serve as a sound alternative to supplementary spinal stabilization.

    View details for Web of Science ID 000226874100012

    View details for PubMedID 15658128

  • A biomechanical comparison of three surgical approaches in bilateral subaxial cervical facet dislocation JOURNAL OF NEUROSURGERY-SPINE Kim, S. M., Lim, J., Paterno, J., Park, J., Kim, D. H. 2004; 1 (1): 108-115

    Abstract

    In bilateral cervical facet dislocation, biomechanical stabilities between anterior locking screw/plate fixation after anterior cervical discectomy and fusion (ACDFP) and posterior transpedicular screw/rod fixation after anterior cervical discectomy and fusion (ACDFTP) have not been compared using the human cadaver, although ACDFP has been performed frequently. In this study the stability of ACDFP, a posterior wiring procedure after ACDFP (ACDFPW), and ACDFTP for treatment of bilateral cervical facet dislocation were compared.Spines (C3-T1) from 10 human cadavers were tested in the intact state, and then after ACDFP, ACDFPW, and ACDFTP were performed. Intervertebral motion was measured using a video-based motion capture system. The range of motion (ROM) and neutral zone (NZ) were compared for each loading mode to a maximum of 2 Nm. The ROM for spines treated with ACDFP was below that of the intact spine in all loading modes, with statistical significance in flexion and extension, but NZs were decreased in flexion and extension and slightly increased in bending and axial rotation; none of these showed statistical significance. The ACDFPW produced statistically significant additional stability in axial rotation ROM and in flexion NZ than ACDFP. The ACDFTP provided better stability than ACDFP in bending and axial rotation, and better stability than ACDFPW in bending for both ROM and NZ. There was no significant difference in extension with either ROM or NZ for the three fixation methods.The spines treated with ACDFTP demonstrated the most effective stabilization, followed by those treated with ACDFPW, and then ACDFP. The spines receiving ACDFP also revealed a higher stability than the intact spine in most loading modes; thus ACDFP can also provide a relatively effective stabilization in bilateral cervical facet dislocation, but with the aid of a brace.

    View details for Web of Science ID 000225714000018

    View details for PubMedID 15291030

  • Cauda equina syndrome in patients with low lumbar fractures. Neurosurgical focus Thongtrangan, I., Le, H., Park, J., Kim, D. H. 2004; 16 (6)

    Abstract

    Symptoms of cauda equina syndrome (CES) can include low-back pain, sciatica, lower-extremity weakness, sensory deficit, perineal hypesthesia or anesthesia, and loss of bowel or bladder function. Several causes of the syndrome are recognized, but its optimal treatment remains controversial and has been broadly based on data gathered from series involving herniated discs. Information on the treatment of CES caused by low lumbar traumatic injuries has not been well documented.Between January 2000 and December 2003, 17 consecutive cases of CES caused by low lumbar traumatic injuries at L2-5 were identified. The traumatic injuries consisted of gun shot wound in two cases, motor vehicle accident in 11, and a fall from height in four. Conus medullaris injuries causing CES were excluded from this review. Presenting symptoms, mechanisms of injury, radiographic images, timing of surgery, surgical approaches, and neurological status at the final follow up were documented. All patients underwent follow up of at least 12 months. Fourteen of 17 patients had satisfactory outcomes. Despite undergoing surgery within the first 24 hours postinjury, three patients had what was classified as a poor outcome given their residual deficits and included two cases with gunshot injuries. Recovery of leg weakness occurred within 4 months, whereas bladder and bowel function recovered within 3 months. All patients in this series underwent decompression within less than 48 hours after syndrome onset. Overall, the authors found no difference regarding timing of surgery between patients in the satisfactory outcome group and those in the poor outcome group.Based on the evidence in this study, the severity of a patient's condition on initial presentation is the most crucial factor in predicting outcome following CES due to low lumbar injuries. Although the matter of the timing of surgery remains controversial, the authors of this study recommend that surgery be performed within 48 hours of syndrome onset.

    View details for PubMedID 15202876

  • Minimally invasive spinal surgery: a historical perspective. Neurosurgical focus Thongtrangan, I., Le, H., Park, J., Kim, D. H. 2004; 16 (1): E13-?

    Abstract

    The concept of minimally invasive spinal surgery embodies the goal of achieving clinical outcomes comparable to those of conventional open surgery, while minimizing the risk of iatrogenic injury that may be incurred during the exposure process. The development of microscopy, laser technology, endoscopy, and video and image guidance systems provided the foundation on which minimally invasive spinal surgery is based. Minimally invasive treatments have been undertaken in all areas of the spinal axis since the 20th century. Lumbar disc disease has been treated using chemonucleolysis, percutaneous discectomy, laser discectomy, intradiscal thermoablation, and minimally invasive microdiscectomy techniques. The initial use of thoracoscopy for thoracic discs and tumor biopsies has expanded to include deformity correction, sympathectomy, vertebrectomy with reconstruction and instrumentation, and resection of paraspinal neurogenic tumors. Laparoscopic techniques, such as those used for appendectomy or cholecystectomy by general surgeons, have evolved into procedures performed by spinal surgeons for anterior lumbar discectomy and fusion. Image-guided systems have been adapted to facilitate pedicle screw placement with increased accuracy. Over the past decade, minimally invasive treatment of cervical spinal disorders has become feasible by applying technologies similar to those developed for the thoracic and lumbar spine. Endoscope-assisted transoral surgery, cervical laminectomy, discectomy, and foraminotomy all represent the continual evolution of minimally invasive spinal surgery. Further improvement in optics and imaging resources, development of biological agents, and introduction of instrumentation systems designed for minimally invasive procedures will inevitably lead to further applications in minimally invasive spine surgery.

    View details for PubMedID 15264791

  • Vertebral body replacement with an expandable cage for reconstruction after spinal tumor resection. Neurosurgical focus Thongtrangan, I., Balabhadra, R. S., Le, H., Park, J., Kim, D. H. 2003; 15 (5): E8-?

    Abstract

    The authors report their clinical experience with expandable cages used to stabilize the spine after vertebrectomy. The objectives of surgical treatment for spine tumors include a decrease in pain, decompression of the neural elements, mechanical stabilization of the spine, and wide resection to gain local control of certain primary tumors. Most of the lesions occur in the anterior column or vertebral body (VB). Anterior column defects following resection of VBs require surgical restoration of anterior column support. Recently, various expandable cages have been developed and used clinically for VB replacement (VBR).Between January 2001 and June 2003, the authors treated 15 patients who presented with primary spinal tumors and metastatic lesions from remote sites. All patients underwent vertebrectomy, VBR with an expandable cage, and anterior instrumentation with or without posterior instrumentation, depending on the stability of the involved segment. The correction of kyphotic angle was achieved at an average of 20 degrees. Pain scores according to the visual analog scale decreased from 8.4 to 5.2 at the last follow-up review. Patients whose Frankel neurological grade was below D attained at least a one-grade improvement after surgery. All patients achieved immediate stability postsurgery and there were no significant complications related to the expandable cage.The advantage of the expandable cage is that it is easy to use because it permits optimal fit and correction of the deformity by in vivo expansion of the device. These results are promising, but long-term follow up is required.

    View details for PubMedID 15323465

  • Surgical Treatment of Tumors Involving Cervicothoracic Junction Neurosurgery Focus Le H, Balahadra RSV, Park J, Kim DH 2003: E3
  • Effect of Frameless Stereotaxy on Accuracy of C1-C2 Transarticular Screw Placement J Neurosurgery Bloch O, Holly LT, Park J 2001; 95: 74-79
  • Thoracolumbar Vertebral Reconstruction for Metastatic Spine Tumors Neurosurgery Villavicencio AT, Oskouian RJ, Roberson C, Stokes J, Park J, Shaffrey CI, Johnson JP 2000; 47: 530-531

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