Clinical Focus

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

Academic Appointments

Administrative Appointments

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

Honors & Awards

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

Professional Education

  • Medical Education:University of Rochester School of Medicine and Dentistry (1993) NY
  • 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)
  • 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.


2015-16 Courses

Graduate and Fellowship Programs


All Publications

  • Sacral Peak Pressure in Healthy Volunteers and Patients With Spinal Cord Injury With and Without Liquid-Based Pad NURSING RESEARCH Duetzmann, S., Forsey, L. M., Senft, C., Seifert, V., Ratliff, J., Park, J. 2015; 64 (4): 300-305
  • Biomechanical Analysis of a Novel Pedicle Screw Anchor Designed for the Osteoporotic Population WORLD NEUROSURGERY Gates, T. A., Moldavsky, M., Salloum, K., Dunbar, G. L., Park, J., Bucklen, B. 2015; 83 (6): 965-969


    The biomechanical study was performed to investigate the effect of a novel pedicle screw anchor in increasing the pullout strength of pedicle screws.Ten lumbar vertebral bodies with a weighted average T-score of -2.13 were used. Pedicle screws of 4.5 mm diameter and 25 mm length were inserted in to one pedicle randomly and matched with an anchor in the corresponding pedicle. Fatigue testing was performed by applying an axial load of ±200N to the screw tulip, along the axis of the rod, at a rate of 0.5 Hz for 1,000 cycles. After fatigue loading was completed, all screws underwent axial pullout testing at a rate of 0.1 mm/sec until failure. A paired two sample for means t-test was performed to determine a significant difference between the two groups (p ≤ 0.05).Following fatigue testing, the axial displacement at the 1,000 cycle point for the anchor and non-anchor group was 1.4 ± 0.7mm and 2.9 ± 1.2mm, respectively. The anchor group had significantly lower axial displacement compared to the non-anchor group (p ≤ 0.01). The group with the anchor reached an average maximum load of 702 ± 373N. The average yield load for the non-anchor group was 421 ± 293N. The anchor group yield load was significantly greater than the non-anchor group (p ≤ 0.01).A novel anchor for standard pedicle screws resulted in significantly less axial movement during fatigue and a greater failure force compared a screw with no anchor. The anchor may provide a stronger bone-to-screw interface, than a non-anchor screw, without the complications of cement augmentation.

    View details for DOI 10.1016/j.wneu.2015.01.057

    View details for Web of Science ID 000356138800016

    View details for PubMedID 25779853

  • Biomechanical Comparisons of Pull Out Strengths After Pedicle Screw Augmentation with Hydroxyapatite, Calcium Phosphate, or Polymethylmethacrylate in the Cadaveric Spine WORLD NEUROSURGERY Yi, S., Rim, D., Park, S. W., Murovic, J. A., Lim, J., Park, J. 2015; 83 (6): 976-981


    In vertebrae with low bone mineral densities pull out strength is often poor, thus various substances have been used to fill screw holes before screw placement for corrective spine surgery. We performed biomechanical cadaveric studies to compare nonaugmented pedicle screws versus hydroxyapatite, calcium phosphate, or polymethylmethacrylate augmented pedicle screws for screw tightening torques and pull out strengths in spine procedures requiring bone screw insertion.Seven human cadaveric T10-L1 spines with 28 vertebral bodies were examined by x-ray to exclude bony abnormalities. Dual-energy x-ray absorptiometry scans evaluated bone mineral densities. Twenty of 28 vertebrae underwent ipsilateral fluoroscopic placement of 6-mm holes augmented with hydroxyapatite, calcium phosphate, or polymethylmethacrylate, followed by transpedicular screw placements. Controls were pedicle screw placements in the contralateral hemivertebrae without augmentation. All groups were evaluated for axial pull out strength using a biomechanical loading frame.Mean pedicle screw axial pull out strength compared with controls increased by 12.5% in hydroxyapatite augmented hemivertebrae (P = 0.600) and by 14.9% in calcium phosphate augmented hemivertebrae (P = 0.234), but the increase was not significant for either method. Pull out strength of polymethylmethacrylate versus hydroxyapatite augmented pedicle screws was 60.8% higher (P = 0.028).Hydroxyapatite and calcium phosphate augmentation in osteoporotic vertebrae showed a trend toward increased pedicle screw pull out strength versus controls. Pedicle screw pull out force of polymethylmethacrylate in the insertion stage was higher than that of hydroxyapatite. However, hydroxyapatite is likely a better clinical alternative to polymethylmethacrylate, as hydroxyapatite augmentation, unlike polymethylmethacrylate augmentation, stimulates bone growth and can be revised.

    View details for DOI 10.1016/j.wneu.2015.01.056

    View details for Web of Science ID 000356138800018

    View details for PubMedID 25769482

  • Spinal Sealant System Provides Better Intraoperative Watertight Closure Than Standard of Care During Spinal Surgery A Prospective, Multicenter, Randomized Controlled Study SPINE Wright, N. M., Park, J., Tew, J. M., Kim, K. D., Shaffrey, M. E., Cheng, J., Choudhri, H., Krishnaney, A. A., Graham, R. S., Mendel, E., Simmons, N. 2015; 40 (8): 505-513


    Prospective, 3:1 randomized, single-blind, multicenter investigational study.To assess the safety and efficacy of a low-swell spinal sealant when used as an adjunct to sutured dural repair compared with standard of care methods to obtain watertight dural closure in subjects undergoing spinal surgery.Watertight dural closure is paramount in spinal surgery to avoid complications of cerebrospinal fluid leak. Prior reports have proven the efficacy of a synthetic, absorbable polyethylene glycol (PEG) hydrogel sealant in spinal surgery compared with standard of care. Given the potential concerns of swelling in spinal applications, the hydrogel was modified to a low-swell formulation.The primary endpoint was success rate in obtaining intraoperative watertight dural closure in subjects receiving PEG hydrogel sealant versus a control group of subjects receiving any standard method designed to provide intraoperative watertight closure. Subjects were evaluated at discharge and at 30 and 90 days postprocedure for cerebrospinal fluid leaks, surgical site infections, and adverse events.Between May 2007 and May 2009, 98 subjects (74 PEG hydrogel spinal sealant, 24 control) were randomized at 14 clinical sites in the United States. Patients treated with the PEG hydrogel spinal sealant had a significantly higher rate of watertight closure than the control (98.6% vs. 79.2%, P = 0.003). No statistical differences were seen in postoperative cerebrospinal fluid, infection, and wound healing. No neurological deficits were seen attributable to the sealant.The low-swell PEG hydrogel spinal sealant evaluated in this study has been proven safe and effective for providing watertight closure when used as an adjunct to sutured closure of intentional durotomies during spinal surgery. PEG hydrogel sealants have again proved superior to other standard of care technologies for safe, efficacious dural closure.2.

    View details for DOI 10.1097/BRS.0000000000000810

    View details for Web of Science ID 000352787100011

    View details for PubMedID 25646746

  • Biomechanical Comparison of Cervical Fixation via Transarticular Facet Screws without Rods versus Lateral Mass Screws with Rods WORLD NEUROSURGERY Yi, S., Rim, D., Nam, K., Keem, S., Murovic, J. A., Lim, J., Park, J. 2015; 83 (4): 548-552


    Transarticular facet screws restore biomechanical stability to the cervical spine when posterior cervical anatomy has been compromised. This study compares the more recent, less invasive, and briefer transarticular facet screw system without rods with the lateral mass screw system with rods.For this study, 6 human cervical spines were obtained from cadavers. Transarticular facet screws without rods were inserted bilaterally into the inferior articular facets at the C5-C6 and C5-C6-C7 levels. Lateral mass screws with rods were inserted bilaterally at the same levels using Magerl's technique. All specimens underwent range of motion (ROM) testing by a material testing machine for flexion, extension, lateral bending, and axial rotation.Both fixation methods, transarticular facet screws without rods and lateral mass screws with rods, reduced all ROM measurements and increased spinal stiffness. No statistically significant differences between the 2 stabilization methods were found in ROM measurements for 1-level insertions. However, in 2-level insertions, ROM for the nonrod transarticular facet screw group was significantly increased for flexion-extension and lateral bending.Transarticular facet screws without rods and lateral mass screws with rods had similar biomechanical stability in single-level insertions. For 2-level insertions, transarticular facet screws without rods are a valid option in cervical spine repair.

    View details for DOI 10.1016/j.wneu.2014.12.008

    View details for Web of Science ID 000353039500032

  • Does a Medial Retraction Blade Transmit Direct Pressure to Pharyngeal/Esophageal Wall During Anterior Cervical Surgery? SPINE Han, I. H., Lee, S. H., Lee, J. M., Kim, H. S., Nam, K. H., Duetzmann, S., Park, J., Choi, B. K. 2015; 40 (1): E18-E22


    A prospective study of 25 patients who underwent anterior cervical surgery.To assess retraction pressure and the exposure of pharyngeal/esophageal (P/E) wall to the medial retractor blade to clarify whether medial retraction causes direct pressure transmission to the P/E wall.Retraction pressure on P/E walls has been used to explain the relation between the retraction pressure and dysphagia or the efficacies of new retractor blades. However, it is doubtful whether the measured pressure represent real retraction pressure on the P/E wall because exposure of the P/E in the surgical field could be reduced by the shielding effect of thyroid cartilage.Epi- and endoesophageal pressures were serially measured using online pressure transducers 15 minutes before retraction, immediately after retraction, and 30 minutes after retraction. To measure the extent of P/E wall exposure to pressure transducer, we used posterior border of thyroid cartilage as a landmark. Intraoperative radiograph was used to mark the position of the posterior border of thyroid cartilage. We checked out the marked location on retractors by measuring the distance from distal retractor tip.The mean epiesophageal pressure significantly increased after retraction (0 mmHg: 88.7 ± 19.6 mmHg: 81.9 ± 15.3 mmHg). The mean endoesophageal pressure minimally changed after retraction (9.0 ± 6.6 mmHg: 15.7 ± 13.8 mmHg: 17.0 ± 14.3 mmHg). The mean location of the posterior border of thyroid cartilage was 7.3 ± 3.5 mm on the retractor blade from the tip, which means epiesophageal pressure was measured against the posterior border of thyroid cartilage, not against the P/E wall.We suggest that a medial retraction blade does not transmit direct pressure on P/E wall due to minimal wall exposure and intervening thyroid cartilage. Our result should be considered when measuring retraction pressure during anterior cervical surgery or designing novel retractor systems.

    View details for DOI 10.1097/BRS.0000000000000649

    View details for Web of Science ID 000346729600003

    View details for PubMedID 25341988

  • Biornechanical Analysis of Disc Pressure and Facet Contact Force After Simulated Two-Level Cervical Surgeries (Fusion and Arthroplasty) and Hybrid Surgery WORLD NEUROSURGERY Park, J., Shin, J. J., Lim, J. 2014; 82 (6)


    The objective of this study was designed to compare 2-level cervical disc surgery (2-level anterior cervical discectomy and fusion [ACDF] or disc arthroplasty) and hybrid surgery (ACDF/arthroplasty) in terms of postoperative adjacent-level intradiscal pressure (IDP) and facet contact force (FCF).Twenty-four cadaveric cervical spines (C3-T2) were tested in various modes, including extension, flexion, and bilateral axial rotation, to compare adjacent-level IDP and FCF after specified treatments as follows: 1) C5-C6 arthroplasty using ProDisc-C (Synthes Spine, West Chester, Pennsylvania, USA) and C6-C7 ACDF, 2) C5-C6 ACDF and C6-C7 arthroplasty using ProDisc-C, 3) 2-level C5-C6/C6-C7 disc arthroplasties, and 4) 2-level C5-C6/C6-C7 ACDF. IDPs were recorded at anterior, central, and posterior disc portions.After 2-level cervical arthrodesis (ACDF), IDP increased significantly at the anterior annulus of distal adjacent-level disc during flexion and axial rotation and at the center of proximal adjacent-level disc during flexion. In contrast, after cervical specified treatments, including disc arthroplasty (2-level disc arthroplasties and hybrid surgery), IDP decreased significantly at the anterior annulus of distal adjacent-level disc during flexion and extension and was unchanged at the center of proximal adjacent-level disc during flexion. Two-level cervical arthrodesis also tended to adversely impact facet loads, increasing distal rather than proximal adjacent-level FCF.Both hybrid surgery and 2-level arthroplasties seem to offer significant advantages over 2-level arthrodesis by reducing IDP at adjacent levels and approximating FCF of an intact spine. These findings suggest that cervical arthroplasties and hybrid surgery are an alternative to reduce IDP and facet loads at adjacent levels.

    View details for DOI 10.1016/j.wneu.2014.06.013

    View details for Web of Science ID 000347635900130

    View details for PubMedID 24937596

  • Directed Axonal Outgrowth Using a Propagating Gradient of IGF-1 ADVANCED MATERIALS Lee, W., Frank, C. W., Park, J. 2014; 26 (29): 4936-4940


    The temporospatial regulation of axon outgrowth is useful for guiding de novo connectivity or re-connectivity of neurons in neurological injury or disease. Here we report the successful construction of a biocompatible guidance device, in which a linear propagation of IGF-1 gradient sequentially directs axon outgrowth. We observe the extensive in vitro axonal extension over 5 mm with a desired growth rate of ∼1 mm/day.

    View details for DOI 10.1002/adma.201305995

    View details for Web of Science ID 000340500700005

    View details for PubMedID 24664530

  • Primary surgical management by reduction and fixation of unstable hangman's fractures with discoligamentous instability or combined fractures: clinical article. Journal of neurosurgery. Spine Shin, J. J., Kim, S. H., Cho, Y. E., Cheshier, S. H., Park, J. 2013; 19 (5): 569-575


    Several controversial issues arise in the management of unstable hangman's fractures. Some surgeons perform external reduction and immobilize the patient's neck in a halo vest, while others perform surgical reduction and internal fixation. The nonsurgical treatments with rigid collar or halo vest immobilization present problems, including nonunion, pseudarthrosis, skull fracture, and scalp laceration and may also fail to achieve anatomical realignment of the local C2-3 kyphosis. With recent advances in surgical technique and technology, surgical intervention is increasingly performed as the primary treatment in high cervical fractures. The outcomes of such surgeries are often superior to those of conservative treatment. The authors propose that surgical intervention as a primary management for hangman's fracture may avoid risks inherent in conservative management when severe circumferential discoligamentous instability is present and may reduce the risk of catastrophic results at the fracture site. The purposes of this study were to assess fracture healing following expedient reduction and surgical fixation and to propose a guideline for treatment of unstable hangman's fractures.From April 2006 to December 2011, the authors treated 105 patients with high cervical fractures. This study included 23 (21.9%) of these patients (15 men and 8 women; mean age 46.4 years) with Type II, IIa, and III hangman's fractures according to the Levine and Edwards classification. The patient's age, sex, mechanism of injury, associated injuries, neurological status, and complications were ascertained. The authors retrospectively assessed the clinical outcome (Neck Disability Index), radiological findings (disc height, translation, and angulation), and bony healing.The average follow-up period was 28.9 months (range 12-63.2 months). The overall average Neck Disability Index score at the time of this study was 6.6 ± 2.3. The average duration of hospitalization was 20.3 days, and fusion was achieved in all cases by 14.8 ± 1.6 weeks after surgery, as demonstrated on dynamic radiographs and cervical 3D CT scans. The mean pretreatment translation was 6.9 ± 3.2 mm, and the mean postoperative translation was 1.6 ± 1.8 mm (mean reduction 5.2 ± 3.1 mm). The initial angulation was 4.7° ± 5.3° and the postoperative angulation was 2.5° ± 1.8° (mean reduction 6.1° ± 5.3°). The preoperative and postoperative values for translation and angulation differed significantly (p < 0.05). The overall C2-3 disc height was 6.7 ± 1.2 mm preoperatively, whereas 3 months after surgery it was 6.4 ± 1.1 mm. These values did not differ significantly (p = 0.0963).The authors observed effective reduction and bony healing in cases of unstable hangman's fractures after fixation, and all patients experienced favorable clinical outcomes with neck pain improvement. The protocols allowed for physiological reconstruction of the fractured deformities and avoided external fixation. The authors suggest that posterior reduction and screw fixation should be used as a primary treatment to promote stability of hangman's fracture in the presence of discoligamentous instability or combined fractures.

    View details for DOI 10.3171/2013.8.SPINE12948

    View details for PubMedID 24033304

  • 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


    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


    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


    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


    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


    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


    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


    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


    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


    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


    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


    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


    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


    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
  • Imaging correlation of the degree of degenerative L4-5 spondylolisthesis with the corresponding amount of facet fluid JOURNAL OF NEUROSURGERY-SPINE Cho, B. Y., Murovic, J. A., Park, J. 2009; 11 (5): 614-619


    The aim of this study was to correlate the degree of L4-5 spondylolisthesis on plain flexion-extension radiographs with the corresponding amount of L4-5 facet fluid visible on MR images.Patients underwent evaluation at the Neurosurgical Spine Clinics of Stanford University Medical Center and National Health Insurance Medical Center (Goyang, South Korea) between January 2006 and December 2007. Only patients who were diagnosed with L4-5 degenerative spondylolisthesis (DS) and who had both lumbosacral flexion-extension radiographs and MR images available for review were eligible for this study. Each patient's dynamic motion index (DMI) was measured using the lateral lumbosacral plain radiograph and was the percentage of the degree of anterior slippage seen on flexion versus that seen on extension. Axial T2-weighted MR images of the L4-5 facet joints obtained in each patient was analyzed for the amount of facet fluid, using the image showing the widest portion of the facets. The facet fluid index was calculated from the ratio of the sum of the amounts of facet fluid found in the right plus left facets over the sum of the average widths of the right plus left facet joints.Fifty-four patients with L4-5 DS were included in this study. Of these 54 patients, facet fluid was noted on MR images in 29 patients (53.7%), and their mean DMI was 6.349 +/- 2.726. Patients who did not have facet fluid on MR imaging had a mean DMI of 1.542 +/- 0.820; this difference was statistically significant (p < 0.001). There was a positive linear association between the facet fluid index and the DMI in the group of patients who exhibited facet fluid on MR images (Pearson correlation coefficient 0.560, p < 0.01). In the subgroup of 29 patients with L4-5 DS who showed facet fluid on MR images, flexion-extension plain radiographs in 10 (34.5%) showed marked anterolisthesis, while the corresponding MR images did not.There is a linear correlation between the degree of segmental motion seen on flexion-extension plain radiography in patients with DS at L4-5 and the amount of L4-5 facet fluid on MR images. If L4-5 facet fluid in patients with DS is seen on MR images, a corresponding anterolisthesis on weight-bearing flexion-extension lateral radiographs should be anticipated. Obtaining plain radiographs will aid in the diagnosis of anterolisthesis caused by an L4-5 hypermobile segment, which may not always be evident on MR images obtained in supine patients.

    View details for DOI 10.3171/2009.6.SPINE08413

    View details for Web of Science ID 000271244200023

    View details for PubMedID 19929367

  • 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


    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



    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


    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


    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


    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)


    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-?


    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

  • Surgical treatment of tumors involving the cervicothoracic junction. Neurosurgical focus Le, H., Balabhadra, R., Park, J., Kim, D. 2003; 15 (5): E3-?


    Tumors involving the cervicothoracic junction can have a high propensity for causing instability, with kyphosis and spinal cord compression resulting. Treatment with decompression only can lead to further instability and worsening neurological status. In this article, the authors review their surgical experience in the treatment of 19 patients with tumors involving the cervicothoracic junction. The various approaches and instrumentation techniques involved in decompression and stabilization of the cervicothoracic junction are also reviewed.Aggressive instrumentation-augmented fusion after decompression of the cervicothoracic region can provide for immediate stabilization and early rehabilitation. Recent development of new hardware such as dual-diameter transition rods, polyaxial screws, and interlocking devices have enhanced the ability to fashion a strong construct for stabilization of the cervicothoracic junction.Familiarity with complex instrumentation techniques and various surgical approaches to the cervicothoracic junction will be required for effective treatment of tumors causing instability of this region.

    View details for PubMedID 15323460

  • 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-?


    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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