A Prospective Study of Lumbar Facet Arthroplasty in the Treatment of Degenerative Spondylolisthesis and Stenosis: Results from the Total Posterior Spine System (TOPS) IDE Study.

STUDY DESIGN: Prospective randomized Food and Drug Administration investigational device exemption clinical trial. OBJECTIVE: The purpose of the present study is to report the 1-year clinical and radiographic outcomes and safety profile of patients who underwent lumbar facet arthroplasty through implantation of the Total Posterior Spine System (TOPS) device. SUMMARY OF BACKGROUND DATA: Lumbar facet arthroplasty is one proposed method of dynamic stabilization to treat grade-1 spondylolisthesis with stenosis; however, there are currently no Food and Drug Administration-approved devices for facet arthroplasty. METHODS: Standard demographic information was collected for each patient. Radiographic parameters and patient-reported outcome measures were assessed preoperatively and at regular postoperative intervals. Complication and reoperation data were also collected for each patient. RESULTS: At the time of this study, 153 patients had undergone implantation of the TOPS device. The mean surgical time was 187.8 minutes and the mean estimated blood loss was 205.7cc. The mean length of hospital stay was 3.0 days. Mean Oswestry Disability Index, Visual Analog Score leg and back, and Zurich Claudication Questionnaire scores improved significantly at all postoperative time points ( P >0.001). There were no clinically significant changes in radiographic parameters, and all operative segments remained mobile at 1-year follow-up. Postoperative complications occurred in 11 patients out of the 153 patients (7.2%) who underwent implantation of the TOPS device. Nine patients (5.9%) underwent a total of 13 reoperations, 1 (0.6%) of which was for device-related failure owing to bilateral L5 pedicle screw loosening. CONCLUSIONS: Lumbar facet arthroplasty with the TOPS device demonstrated a statistically significant improvement in all patient-reported outcome measures and the ability to maintain motion at the index level while limiting sagittal translation with a low complication rate.

Determining C2 Pedicle Screw Placement Feasibility in the Pediatric Population: A Computed Tomographic Safe Zone Analysis.

BACKGROUND: Due to high rates of anatomic variability of the C2 pedicle, thin-sliced pedicular-oriented computed tomography (CT) and 3-dimensional reconstructive CT technologies have been introduced to predict safe C2 pedicle screw placement. However, this technology may not be readily available in all centers. The purpose of this study was to perform a C2 pedicle safe zone analysis using standard sagittal CT scans to predict the feasibility of C2 pedicle screw placement in a pediatric population and to compare the results with our previously obtained safe zone analysis from the adult population. METHODS: A retrospective analysis was performed at a single level I trauma center of pediatric patients who completed CT scans of the cervical spine. The feasibility of C2 pedicle screw placement was analyzed using our previously described C2 pedicle safe zone analysis technique. The risk profiles were compared with our previously obtained safe zone analysis from the adult population. RESULTS: Thirty-nine consecutive patients with a mean age of 7.8±4.4 years and 78 total pedicles were included in the study. Fourteen pedicles (18%) were considered low risk, 37 (47%) were moderate risk, and 27 (35%) were high risk for vertebral artery injury. Individual patients were found to have a significant amount of side-to-side variability between pedicles with 21 patients (54%) having left and right pedicles with different risk profiles. Four patients (10%) demonstrated low risk profiles in bilateral pedicles. There was no significant difference between the risk profiles of pediatric and adult patients. CONCLUSIONS: There is a considerable amount of anatomic variability within the pediatric C2 pedicles. Using this simple and accessible technique during the review of preoperative imaging, C2 pedicle screw placement may be considered in appropriately selected pediatric patients. LEVEL OF EVIDENCE: Level III.

Radiologic Analysis of C2 to Predict Safe Placement of Pedicle Screws.

BACKGROUND: Preoperative assessment of C2 pedicle morphology is critical to safe pedicle screw placement. To avoid iatrogenic injury, complex digital templating software has been introduced; however, this technology may not be available in many centers. We report a technique for preoperative assessment of C2 pedicle screw placement safety based upon 2-dimensional sagittal computed tomography (CT) scan images and verify its utility in clinical practice. METHODS: A total of 46 consecutive patients underwent cervical spine CT scans between 2005 and 2011. The C2 pedicle morphology was assessed on sagittal CT imaging by 5 independent reviewers to determine the feasibility and risk associated with pedicle screw placement. Thirty consecutive patients underwent C2 pedicle screw placement and were followed clinically for a minimum of 2 years. The ability to place a screw was noted, and accuracy of screw placement was assessed postoperatively by CT scan. RESULTS: The CT scan analysis demonstrated that 11% (5/46) of patients had sufficient pedicle size bilaterally to allow safe placement of long pedicle screws with a low risk of vertebral artery injury, whereas 15% (7/46) were considered a high risk bilaterally. Screw placement was deemed low risk in 28%, moderate risk in 38%, and high risk in 34%. Excellent intraobserver reliability and good interobserver reliability was observed. Clinically, 18 of 20 (90%) low-risk and 21 of 24 (88%) moderate-risk pedicle screws were placed safely versus 5 of 16 (31%) high-risk pedicle screws (P < .001). CONCLUSIONS: Using the described technique for evaluating the C2 pedicle via sagittal CT scan images allows for safe and reliable pedicle screw placement without relying upon complex digital templating software, which may have limited availability. LEVEL OF EVIDENCE: II. CLINICAL RELEVANCE: This study aids in the surgical decision-making behind the placement of C2 pedicle screws using CT scans without reliance upon complex digital templating software.

Thoracolumbar burst fractures treated with posterior decompression and pedicle screw instrumentation supplemented with balloon-assisted vertebroplasty and calcium phosphate reconstruction. Surgical technique.

BACKGROUND: The treatment of unstable thoracolumbar burst fractures with short-segment posterior spinal instrumentation without anterior column reconstruction is associated with a high rate of screw breakage and progressive loss of reduction. The purpose of the present study was to evaluate the functional, neurologic, and radiographic results following transpedicular, balloon-assisted fracture reduction with anterior column reconstruction with use of calcium phosphate bone cement combined with short-segment posterior instrumentation and a laminectomy. METHODS: A consecutive series of thirty-eight patients with an unstable thoracolumbar burst fracture with or without neurologic deficit were managed with transpedicular, balloon-assisted fracture reduction, calcium phosphate bone cement reconstruction, and short-segment spinal instrumentation from 2002 to 2005. Twenty-eight of the thirty-eight patients were followed for a minimum of two years. Demographic data, neurologic function, segmental kyphosis, the fracture severity score, canal compromise, the Short Form-36 score, the Oswestry Disability Index score, and treatment-related complications were evaluated prospectively. RESULTS: All thirteen patients with incomplete neurologic deficits had improvement by at least one Frankel grade. The mean kyphotic angulation improved from 17 degrees preoperatively to 7 degrees at the time of the latest follow-up, and the loss of vertebral body height improved from a mean of 42% preoperatively to 14% at the time of the latest follow-up. Screw breakage occurred in two patients, and pseudarthrosis occurred in one patient. CONCLUSIONS: The present study demonstrates that excellent reduction of unstable thoracolumbar burst fractures with and without associated neurologic deficits can be maintained with use of short-segment instrumentation and a transpedicular balloon-assisted reduction combined with anterior column reconstruction with calcium phosphate bone cement performed through a single posterior incision. The resultant circumferential stabilization combined with a decompressive laminectomy led to maintained or improved neurologic function in all patients with neurologic deficits, with a low rate of instrumentation failure and loss of correction.

Thoracolumbar burst fractures treated with posterior decompression and pedicle screw instrumentation supplemented with balloon-assisted vertebroplasty and calcium phosphate reconstruction.

BACKGROUND: The treatment of unstable thoracolumbar burst fractures with short-segment posterior spinal instrumentation without anterior column reconstruction is associated with a high rate of screw breakage and progressive loss of reduction. The purpose of the present study was to evaluate the functional, neurologic, and radiographic results following transpedicular, balloon-assisted fracture reduction with anterior column reconstruction with use of calcium phosphate bone cement combined with short-segment posterior instrumentation and a laminectomy. METHODS: A consecutive series of thirty-eight patients with an unstable thoracolumbar burst fracture with or without neurologic deficit were managed with transpedicular, balloon-assisted fracture reduction, calcium phosphate bone cement reconstruction, and short-segment spinal instrumentation from 2002 to 2005. Twenty-eight of the thirty-eight patients were followed for a minimum of two years. Demographic data, neurologic function, segmental kyphosis, the fracture severity score, canal compromise, the Short Form-36 score, the Oswestry Disability Index score, and treatment-related complications were evaluated prospectively. RESULTS: All thirteen patients with incomplete neurologic deficits had improvement by at least one Frankel grade. The mean kyphotic angulation improved from 17 degrees preoperatively to 7 degrees at the time of the latest follow-up, and the loss of vertebral body height improved from a mean of 42% preoperatively to 14% at the time of the latest follow-up. Screw breakage occurred in two patients, and pseudarthrosis occurred in one patient. CONCLUSIONS: The present study demonstrates that excellent reduction of unstable thoracolumbar burst fractures with and without associated neurologic deficits can be maintained with use of short-segment instrumentation and a transpedicular balloon-assisted reduction combined with anterior column reconstruction with calcium phosphate bone cement performed through a single posterior incision. The resultant circumferential stabilization combined with a decompressive laminectomy led to maintained or improved neurologic function in all patients with neurologic deficits, with a low rate of instrumentation failure and loss of correction.

Risk factors for osteoporosis at the knee in the spinal cord injury population.

BACKGROUND: The objective of this study was to determine modifiable and nonmodifiable risk factors for bone loss at the knee in individuals with spinal cord injury (SCI) by examining known risk factors for osteoporosis in the general population and additional, unique nonmodifiable SCI elements including age at injury onset, injury duration, and extent of neurologic injury (level and completeness). METHODS: Risk factors were examined by logistic regression in 152 individuals with chronic SCI. Knees were classified as osteoporotic based on whether bone mineral density (BMD) of the knee as assessed by dual-energy x-ray absorptiometry fell within the 95% confidence interval of the BMD of the knee of individuals who had experienced fractures at the knee. RESULTS: Accuracy for predicted membership in the osteoporotic group and nonosteoporotic group were 79.22% and 69.33%, respectively. Of all variables included in the analysis, 3 had a significant effect on predicted group membership: completeness of injury (P < 0.0001), body mass index (BMI) (P = 0.0035), and age (P = 0.0394). Individuals with complete injuries were 6.17 times (617%) more likely to have BMD of the knee low enough to place them in the osteoporotic category. The odds ratio for BMI indicated that every unit increase in BMI lowered the odds of being in the osteoporotic group by 11.29%. The odds ratio for age indicated that every 1-year increase in age increased the odds of being in the osteoporotic group by 3.54%. No other modifiable or nonmodifiable risk factors were significant predictors. CONCLUSION: Completeness of injury dictates and overrides most modifiable and nonmodifiable risk factors for bone loss at the knee leading to pathologic fractures in SCI. SCI osteoporosis may be classified more appropriately as neurogenic in origin.