Faculty Bibliography

BACKGROUND CONTEXT: Surgery for degenerative spondylolisthesis (DS) is common with good clinical outcomes. Several high quality studies have examined outcomes following DS surgery, but few have identified risk factors for re-operation. PURPOSE: To investigate the incidence of re-operation and associated risk factors among the surgically treated patients from the DS arm of the Spine Patient Outcomes Research Trial (SPORT), randomized and observational cohorts. Our study hypothesis was that certain patient characteristics would emerge as risk factors for re-operation. STUDY DESIGN/SETTING: A retrospective subgroup analysis of the 8- year data from the SPORT trial. PATIENT SAMPLE: 406 patients who underwent surgery for DS. OUTCOME MEASURES: Incidence of re-operation, risk factors. METHODS: A retrospective subgroup analysis was performed on surgically treated patients enrolled in the DS arm of the multicenter SPORT trial, randomized and observational cohorts. Included patients had neurogenic claudication for at least 12 weeks, clinical neurological signs, spinal stenosis on cross-sectional imaging, and DS on standing lateral radiographs. In our subgroup analysis, patients were stratified into no re-operation versus re-operation. Baseline characteristics were analyzed using multivariate regression from data collected from patients at eight years postoperatively. A Cox regression model Stepwise Method was implemented in SAS with p=0.10 significant for entry and p=0.05 significant for retention with calculation of hazard ratios (HR). RESULTS: Of the 406 surgery patients, 73% underwent instrumented fusion, 21% non-instrumented fusion, and 6% decompression alone. At 8 years, the re-operation rate was 22%, 315 having no re-operation and 91 in the re-operation group. Twenty-five (28%) were within the first year, 49 (54%) within 2 years, 64 (70%) within 4 years, and 78 (86%) within 6 years. Forty-one revisions (10%) were for progressive DS, 33 (8%) for complication or other reason, and 13 (3%) for a new co!

BACKGROUND CONTEXT: Lumbar spinal stenosis (SpS) is a common degenerative disease involving narrowing of the spinal canal that may lead to pain and disability. Spinal stenosis is the most common indication for surgery in the elderly population and was the fastest growing spine surgery in the last three decades. Prospective studies have shown that timely surgical intervention can be effective in restoring function in these patients, with variable re-operation rates. Few long-term studies have identified consistent risk factors for re-operation following surgery for SpS. PURPOSE: To investigate the incidence of re-operation and associated risk factors among the surgically treated patients from the SpS arm of the Spine Patient Outcomes Research Trial (SPORT), randomized and observational cohorts. Our study hypothesis was that specific patient baseline characteristics would emerge as risk factors for re-operation in patients treated surgically for SpS. STUDY DESIGN/SETTING: A retrospective subgroup analysis of the eight-year data from the SPORT trial. PATIENT SAMPLE: 417 patients who underwent surgery for SpS. OUTCOME MEASURES: Incidence of re-operation, risk factors. METHODS: A retrospective subgroup analysis was performed on surgically treated patients enrolled in the SpS arm of the multicenter SPORT trial randomized and observational cohorts. Patients included in the SpS arm had neurogenic claudication for at least 12 weeks and spinal stenosis, without spondylolisthesis or instability, as confirmed on imaging. In our subanalysis, patients were stratified into no re-operation versus reoperation. Baseline characteristics were analyzed using a multivariate regression analysis based on data collected from patients at eight years postoperatively. A Cox regression model Stepwise Method was implemented in SAS with p=0.10 significant for entry and p=0.05 significant for retention to the model. RESULTS: Of the 417 surgery patients, 88% underwent decompression only, 6% noninstrumented fusion, and 6% instr!

BACKGROUND CONTEXT: Despite recognition of its occurrence, reliable predictors of the development of cervical deformity (CD) following ASD surgery are elusive and the effects unclear. PURPOSE: To quantify the incidence of CD after ASD surgery, identify predictors of development and determines the impact outcomes. STUDY DESIGN/SETTING: Retrospective review of a prospective multicenter ASD database. PATIENT SAMPLE: 215 patients>18 years of age with ASD. OUTCOME MEASURES: Risk factors for development of CD and HRQOL. METHODS: This was a retrospective review of a prospective multicenter database evaluating surgical ASD patients with complete 2-year follow-up. CD was defined by: T1S-CL>20degree, C2C7 SVA>40mm, or C2C7 kyphosis>10degree. Univariate testing was performed using t-tests, or tests of proportion. The impact of CD at 2 years on Health Related Quality of Life (HRQOL) and satisfaction was measured using repeated measures mixed models or logistic regression as appropriate. RESULTS: 215 patients were included. 63% were found to have CD at 2 years postop. CD patients had a higher incidence of preop CD (p=0.0001) and diabetes (p=0.05). They also had lower baseline C2-T3 lordosis (5.49 vs 11.97, p=0.003), lower C2 tilt (71.5 vs 79.28, p=0.0001) and higher C2 slope (18.49 vs 10.71, p=0.0001) and T1 (26.08 vs 22.2, p=0.036) slopes, and C2-S1 SVA (84.32 vs 57.57, p=0.002). Patients with and without CD at 2 years experienced significant improvements in their HRQL scores: SF- 36 (p=0.0001), ODI (p=0.0001) and SRS (p=0.0001). Rates of improvement and overall improvement were similar. CD was not a predictor of 2- year patient satisfaction (p=0.367). CONCLUSIONS: Predictors of CD at 2 years include the presence of the following at baseline: CD, diabetes, higher C2 and T1 slopes, higher C2-S1 SVA, and lower C2-T3 lordosis. Significant improvements in 2-year HRQOL scores occurred in the presence or absence of CD, and patient satisfaction was unaffected. While this study identifies several predictors of CD,!

BACKGROUND CONTEXT: A high prevalence of cervical deformity (CD) has been identified among adult spinal deformity (ASD) patients undergoing surgical treatment. The clinical impact of this is uncertain. PURPOSE: This study aims to quantify the difference in patient-reported outcomes among ASD patients based on presence of CD prior to treatment. STUDY DESIGN/SETTING: Retrospective review of a multicenter prospective database of surgical ASD patients with 2-year follow-up. PATIENT SAMPLE: 235 patients>18years of age with ASD, of which 65 with pre-op C2C7 SVA>4cm, and 57 with cervical kyphosis (CK). OUTCOME MEASURES: Health Related Quality of Life (HRQL) scores: SF-36, Oswestry Disability Index (ODI), Scoliosis Research Society (SRS), and patients obtaining Minimally Clinically Important Difference (MCID) at 2 years. METHODS: Retrospective review of a multicenter prospective database of surgical ASD patients with 2-year follow-up. CD was defined as: C2C7 SVA>4cm, CK C2C7angle>0. Univariate testing was performed using t-tests, or tests of proportion. Multivariate models determined impact of pre-op CD on HRQL. RESULTS: 235 patients met criteria, of which 65 with pre-op C2C7 SVA>4cm, 57 with CK. Patients with and without CD saw improvements in 2-year HRQL scores (p<0.001). Overall, patients with preop CD had inferior postop HRQL and were less likely to achieve MCID for HRQL at 2 years. Those with preop SVA>4cm had worse ODI, PCS, SRS activity, appearance, pain and total, and were less likely to meet MCID for ODI, PCS, SRS activity and pain scores (odds ratio 0.39 for ODI CI 0.19:0.81 p<0.05), (0.34 for PCS CI 0.16:0.72 p<0.05), (0.29 CI 0.14:0.62 p< 0.05 SRS activity) (0.41 CI 0.20:0.86 p<0.05 SRS pain). Similarly, patients with CK had inferior 2-year HRQL scores. Patients without any CD were 4x more likely to reach 2-year SRS activity MCID (OR 0.40 CI 0.19:0.86 p<0.05). CONCLUSIONS: Despite experiencing significant improvements in HRQL scores, preop CD in ASD patients is a strong predictor of inferio!

BACKGROUND CONTEXT: Patients undergoing adult spinal deformity (ASD) correction are at risk for an unplanned return to surgery due to complications following index surgery vs primary outcomes. Revision surgeries are often more technically challenging, and therefore, it is important to identify predictors to be included in preoperative discussion and to notify known risk factors to patients. However, there is no literature proposing predictors of revision surgery for ASD patients. PURPOSE: To investigate the incidence, predictors and impact on healthrelated quality of life (HRQL) outcomes and patient satisfaction of unplanned return to surgery after ASD correction. STUDY DESIGN/SETTING: Multicenter, retrospective review of consecutive surgical ASD patients. PATIENT SAMPLE: 243 adults treated surgically for spinal deformity. OUTCOME MEASURES: Pre- and postoperative HRQL scores and radiographic parameters, rate and predictors of revision surgery. METHODS: Two-year, multicenter, prospective analysis of surgical adult spinal deformity (ASD) patients (age >18 years and scoliosis >20degree, SVA >5cm, pelvic tilt >25degree, or thoracic kyphosis>60degree). Inclusion criteria for this study were complete demographic, radiographic, HRQL and operative data at 2-year follow-up. Patients were divided into Index Surgery only or Revisions. Primary infections were excluded. Potential predictors and confounders for revision surgery were identified using univariate analysis. Multivariate logistic regression modeling determined predictors of revision and impact on satisfaction. Multivariate repeated measured mixed models measured revision impact on HRQL. RESULTS: 243 patients met inclusion criteria. 42 (17.3%) patients underwent revisions (14.3% at 6 weeks, 38% between 6 weeks and 1 year, and 47.7% between 1-2 years). Non-rod implant complications were the most common indication for revision (9) followed by PJK (8) and rod failure (8). Positive predictors of revision surgery included: weight (OR 1.33 per 10kg incr!

Study Design Literature review. Objective Atlantoaxial dislocation (AAD) is a rare and potentially fatal disturbance to the normal occipital-cervical anatomy that affects some populations disproportionately, which may cause permanent neurologic deficits or sagittal deformity if not treated in a timely and appropriate manner. Currently, there is a lack of consensus among surgeons on the best approach to diagnose, characterize, and treat this condition. The objective of this review is to provide a comprehensive review of the literature to identify timely and effective diagnostic techniques and treatment modalities of AAD. Methods This review examined all articles published concerning "atlantoaxial dislocation" or "atlantoaxial subluxation" on the PubMed database. We included 112 articles published between 1966 and 2014. Results Results of these studies are summarized primarily as defining AAD, the normal anatomy, etiology of dislocation, clinical presentation, diagnostic techniques, classification, and recommendations for timely treatment modalities. Conclusions The Wang Classification System provides a practical means to diagnose and treat AAD. However, future research is required to identify the most salient intervention component or combination of components that lead to the best outcomes.

Study Design. Retrospective analysis.Objective. To determine patient demographics, incidence of comorbidities and procedure-related complications, and identify risk factors associated with morbidity and mortality after spinal surgery for cauda equina syndrome (CES).Summary of Background Data. To our knowledge, no study has provided nationwide estimates of patient characteristics and procedure-related complication rates after spinal surgery for CES relative to an unaffected population.Methods. Nationwide Inpatient Sample data collected between 2001 and 2010 was analyzed. Discharges with procedural codes for lumbar spinal fusion, decompression, or discectomy were included. The CES cohort included diagnoses of CES, and the unaffected cohort included lumbar spinal pathology diagnoses. Patient demographics, incidence of comorbidities and procedure-related complications, and risk factors associated with morbidity and mortality were compared.Results. Discharges for 11,207 CES and 689,799 unaffected patients were identified. Differences between cohorts were found for demographic and hospital data. Average comorbidity indices for the CES cohort were found to be increased (0.23 vs.0.13, p< 0.0001), as well as the incidence of total procedure-related complications (18.63% vs. 13.12%, p< 0.0001). In-hospital mortality rate was significantly increased for the CES cohort (0.30% vs. 0.08%, p< 0.0001). A number of comorbidities associated with additional risk for morbidity and mortality among the CES cohort were identified.Conclusion. Relative to an unaffected population undergoing similar treatment, CES patients were more likely to have increased associated comorbidities on presentation, as well as increased complication rates with a prolonged hospital course postoperatively. CES was found to carry an increased incidence of procedure-related complications as well as in-hospital mortality. A number of comorbidities associated with additional risk for morbidity and mortality among the CES cohort were identified. This study provides clinically useful data for surgeons to educate patients at risk for morbidity and mortality as well as direct future research to improve patient outcomes.

BACKGROUND CONTEXT: Adolescent idiopathic scoliosis (AIS) is a complex multi-plane deformity of the spine that involves a lateral component in the coronal plane in addition to a rotational component affecting all three planes. AIS occurs in otherwise healthy children at or around puberty. The natural history of scoliosis varies significantly depending on curve pattern and pathogenesis. Potential sequelae of untreated AIS include curve progression, back pain, cardiopulmonary problems and psychosocial concerns. Optimal treatment of AIS must weigh the benefits and effectiveness of the intervention against its potential risks. This study aims to better define the risks associated with surgical intervention in AIS patients by comparing the perioperative complications of primary and revision spinal fusions in this population. PURPOSE: The goal of this study is to investigate the rates of perioperative complications of primary and revision spinal fusions for AIS. STUDY DESIGN/SETTING: Retrospective review of national data from a large administrative database. PATIENT SAMPLE: Patients between 10 and 18 years of age with diagnosis of idiopathic scoliosis undergoing primary or revision spinal fusions. OUTCOME MEASURES: Perioperative complications, length of stay, total costs, mortality. METHODS: The national inpatient sample (NIS) database was queried for patients undergoing spinal fusion for AIS between 2001 and 2010. Patients with AIS were identified as those between 10 and 18 years of age with a diagnosis of idiopathic scoliosis as identified with ICD-9 codes. Univariate and multivariate analyses were carried out comparing primary and revision fusions in terms of perioperative complications, length of stay (LOS), total cost of hospitalization and mortality. National estimates of annual total number of procedures were calculated. RESULTS: A total of 48,403 fusions were performed for AIS between 2001 and 2010. Of those fusions 1.3% (630) were revisions. Revision fusions were associated with a higher rat!

Object Lateral mass screws (LMS) have been used extensively with a low complication rate in the subaxial spine. Recently, cervical pedicle screws (CPS) have been introduced, and are thought to provide more optimal stabilization of the subaxial spine in certain circumstances. However, because of the concern for neurovascular injury, the routine use of CPS in this location remains controversial. Despite this controversy, however, there are no articles directly comparing screw-related complications of each procedure in the subaxial cervical spine. The purpose of this study was to evaluate screw-related complications of LMS and CPS in the subaxial cervical spine. Methods A PubMed/MEDLINE and Cochrane Collaboration Library search was executed, using the key words "lateral mass screw" and "cervical pedicle screw." Clinical studies evaluating surgical procedures of the subaxial cervical spine in which either LMS or CPS were used and complications were reported were included. Studies in which the number of patients who had subaxial cervical spine surgery and the number of screws placed from C-3 to C-7 could not be specified were excluded. Data on screw-related complications of each study were recorded and compared. Results Ten studies of LMS and 12 studies of CPS were included in the analysis. Vertebral artery injuries were slightly but statistically significantly higher with the use of CPS relative to LMS in the subaxial cervical spine. Although the use of LMS was associated with a higher rate of screw loosening, screw pullout, loss of reduction, pseudarthrosis, and revision surgery, this finding was not statistically significant. Conclusions Based on the available literature, it appears that perioperative neurological and late biomechanical complication rates, including pseudarthrosis, are similarly low for both LMS and CPS techniques. In contrast, vertebral artery injuries, although statistically significantly more common when using CPS, are extremely rare with both techniques, which may justify their nonroutine use in select cases. Given the paucity of well-designed studies available, this recommendation may be a reflection of deficiencies in the available studies. Surgeons using either technique should have intimate knowledge of cervical anatomy and an adequate preoperative evaluation for each patient, with the final selection based on individual case requirements and anatomical limitations.

PURPOSE: Spinal stenosis at the C2-3 segment is a rare occurrence, and when it occurs myelopathy infrequently results. Furthermore, only a handful of cases involving congenital abnormalities of the posterior arch of the axis have been described resulting in cervical myelopathy many of which described simultaneous congenital abnormalities at adjacent levels and none of which identified ossification of the posterior longitudinal ligament (OPLL) at the same level. We report a case of a previously undescribed combination of abnormalities at the C2-3 segment resulting in clinical myelopathy. METHODS: A 49-year-old Chinese male presented with a progressive cervical myelopathy (C-JOA score 11 immediately pre-op). Segmental OPLL at the C2-3 disk space was visible, together with invagination of the bilaterally hypoplastic C2 lamina into the spinal canal. Signal abnormalities of the spinal cord were evident on both T1 and T2 sequences. RESULTS: The patient underwent a posterior decompression and instrumented fusion at C2-3 using pars screws at C2 and lateral mass screws at C3. Following surgery there was a rapid and significant improvement in the neurological symptoms, with the C-JOA score improving to 14 at final follow-up. A successful fusion was evident. CONCLUSIONS: Deficiencies in the posterior arch of the axis are rare and have not previously been reported in conjunction with OPLL. Advanced imaging is helpful to define the abnormality and site of compression. In the setting of a progressive neurological dysfunction, surgical decompression and stabilization is a reasonable intervention and can be associated with neurological and symptomatic improvement.