Faculty Bibliography

STUDY DESIGN: Retrospective review of an administrative database. OBJECTIVE: To observe New York statewide trends in lumbar spine surgery and to compare utilization of fusion according to hospital size and patient population. SUMMARY OF BACKGROUND DATA: Over the last 30 years, studies have indicated increasing rates of spinal fusion procedures performed each year in the United States. There is no study investigating potential variability in this trend according to hospital volume. METHODS: New York Statewide Planning and Research Cooperative System(SPARCS) administrative data were used to identify 228,882 lumbar spine surgerypatients. New York State hospitals were categorized as low-, medium- or high-volume and descriptive statistics were used to determine trends in spinal fusion. RESULTS: The number of fusions per year increased 55% from 2005-2014. The ratio of fusion to non-fusion surgery increased from 0.88 to 2.67 at high-, from 0.84 to 2.30 at medium- and from 0.66 to 1.52 at low-volume hospitals. In 2014, 22% of spine surgery patients at low-volume hospitals were either African American or Hispanic compared to 12% and 14% at high- and medium-volume hospitals, respectively. At high volume hospitals, 33% of patients were privately insured and 3% had Medicare compared to 30% and 6% at low-volume hospitals. CONCLUSIONS: The annual number of lumbar spinal fusions continues to increase, especially at high- and medium-volume hospitals. The percentage of patients treated surgically for lumbar spinal stenosis (LSS) who undergo fusion ranges from 53.2%-66.4% depending on hospital volume. Individual surgeon opinion, patient disease characteristics, and socioeconomic factors may affect surgical decision-making. Caucasians and private insurance patients most often receive care at high-volume hospitals. Minorities and patients with Medicaid are over-represented at low-volume centers where fusions are less often performed. Accessibility to care at high-volume centers remains a major concern for these vulnerable populations. LEVEL OF EVIDENCE: 3.

BACKGROUND/AIMS: Surgical techniques for effective high-grade spondylolisthesis (HGS) remain controversial. This study aims to evaluate radiographic/clinical outcomes in HGS patients treated using modified "Reverse Bohlman" (RB) technique. METHODS: Review of consecutive HGS patients undergoing RB at a single university-center from 2006 to 2013. Clinical, surgical, radiographic parameters collected. RESULTS: Six patients identified: five with L5-S1 HGS with L4-L5 instability and one had an L4-5 isthmic spondylolisthesis and grade 1 L5-S1 isthmic spondylolisthesis. Two interbody graft failures and one L5-S1 pseudoarthrosis. Postoperative improvement of anterolisthesis (62.3% vs. 49.6%, p = 0.003), slip angle (10 vs. 5 degrees , p = 0.005), and lumbar lordosis (49 vs. 57.5 degrees , p = 0.049). CONCLUSIONS: RB technique for HGS recommended when addressing adjacent level instability/slip.

STUDY DESIGN: Retrospective multicenter database review. OBJECTIVE: The aim of this study was to evaluate national postoperative outcomes and hospital characteristics trends from 2001 to 2010 for advanced age CSM patients. SUMMARY OF BACKGROUND DATA: Recent studies show increases in US cervical spine surgeries and CSM diagnoses. However, few have compared national outcomes for elderly and younger CSM patients. METHODS: A Nationwide Inpatient Sample (NIS) analysis from 2001 to 2010, including CSM patients 25+ who underwent anterior and/or posterior cervical fusion or laminoplasty. Fractures, 9+ levels fused, or any cancers were excluded. Measures included demographics, outcomes, and hospital-related data for 25 to 64 versus 65+ and 65 to 75 versus 76+ age groups. Univariate and logistic regression modeling evaluated procedure-related complications risk in 65+ and 76+ age groups (OR[95% CI]). RESULTS: Discharges for 35,319 patients in the age range of 25 to 64 years and 19,097 at the age 65+ years were identified. Average comorbidity indices for patients at 65+ years were higher compared to the 25 to 64 years age group (0.79 vs. 0.0.44, P < 0.0001), as was the total complications rate (11.39% vs. 5.93%, P < 0.0001) and charges ($57,449.94 vs. $49,951.11, P < 0.0001). Hospital course for aged 65+ patients was longer (4.76 vs. 3.26 days, P < 0.0001). Mortality risk was higher in the 65+ cohort (3.38[2.93-3.91]), adjusted for covariates. 65+ patients had increased risk of all complications except device-related, for which they had decreased risk (0.61[0.56-0.67]). Patients 76+ years displayed increased hospital charges ($59,197.60 vs. $56,601.44, P < 0.001) and courses (5.77 vs. 4.28 days, P < 0.001) compared to those in the age group 65 to 75 years. These same patients presented with increased Deyo scores (0.83 vs. 0.77, P < 0.001), had increased total complications rate (13.87% vs. 10.20%, P < 0.001), and displayed increased risk for postoperative shock (6.34 [11.16-3.60], P < 0.001), digestive system (1.92 [2.40-1.54], P < 0.001), and wound dehiscence (1.71 [2.56-1.15], P < 0.001). CONCLUSION: Patients aged 65+ years undergoing CSM surgical management have a higher mortality risk, more procedure-related complications, higher comorbidity burden, longer hospital course, and higher charges. This study provides clinically useful data for surgeons to educate patients and to improve outcomes.

BACKGROUND: Lateral transpsoas interbody fusion (LTIF) is a minimally invasive technique for achieving lumbar spinal fusion. While it has many advantages over open techniques it carries with it a distinct set of risks, most commonly post-operative ipsilateral thigh pain, weakness and sensory disturbances. It is vital for both the surgeon and patient to understand the risks for and outcomes of injury associated with this procedure. We conducted a systematic review of the literature to evaluate the incidence, risks, and long-term clinical outcomes of post-operative thigh symptoms in patients treated with LTIF. METHODS: We conducted a search of MEDLINE, EMBASE, CINAHL, Scopus, Web of Science and the Cochrane Collaboration Library, using keywords and MeSH terms, for English-language literature published through September 2014, as well as reference lists from key articles. Studies were then manually filtered to retrieve articles that met inclusion criteria. We were interested in studies that reported postoperative lower extremity symptoms after LTIF, such as pain, weakness and changes in sensation. The strength of evidence was determined based on precepts outlined by the Grades of Recommendation Assessment, Development and Evaluation Working Group (GRADE). RESULTS: A total of 392 articles were initially retrieved, with 24 ultimately meeting criteria for inclusion. The incidence of any post-operative thigh symptom varied, ranging as high as 60.7%, with 9.3% of patients experiencing a motor deficit related to direct nerve injury. Several studies reported cases of persistent symptoms at 6 months follow up. Additionally, inclusion of the L4-5 disc space and a longer duration of surgery were both identified as risks for developing postoperative thigh symptoms. CONCLUSION: The risk of postoperative thigh symptoms after LTIF is high. Thigh pain, paresthesias and weakness were the most commonly reported symptoms. While most patients' symptoms resolved by 6 months follow up, several studies reported patients with symptoms persistent as far as 12 months removed from surgery. Surgery at the L4-5 disc space and longer surgical duration place the patient at greater risk for developing postoperative and long-term thigh symptoms.

Intraoperative neuromonitoring has proved to be a valuable and safe technique for assessing patients' neurologic status during spine surgery. The effects of anesthesia and the feasibility of obtaining intraoperative neuromonitoring signals during spine surgery have been well investigated. Total intravenous anesthesia appears to be the most reliable and consistent at allowing attainment of neuromonitoring signals. Motor evoked potentials are most vulnerable to anesthetic agents. Changes in neuromonitoring signals observed during spine surgery may be caused by multiple factors. Establishing a standard protocol to investigate changes in intraoperative neuromonitoring signals is important and may prove valuable in preventing neurologic complications

BACKGROUND CONTEXT: Degenerative lumbar stenosis (DLS) patients adopt forward-bending posture as a compensatory mechanism, increasing spinal canal and foraminal volume. Previous data show laminectomy 6 short segment fusion results in improvement of sagittal vertical axis (SVA), pelvic tilt (PT) and PI-LL (pelvic incidence-lumbar lordosis) mismatch by SRS-Schwab classification in <25% of patients. The magnitude of deformity for which a DLS patient should have realignment remains unknown. PURPOSE: To identify differences in compensatory mechanisms between DLS and adult spinal deformity (ASD) patients with increasing, and to identify at what point DLS patients recruit ASD-type compensatory mechanisms. STUDY DESIGN/SETTING: Retrospective clinical and radiological review. PATIENT SAMPLE: Baseline X-ray images of 239 patients without spinal instrumentation, with the clinical radiological and diagnosis of DLS or ASD were assessed for patterns of spino-pelvic compensatory mechanisms. Patients were stratified by sagittal vertical axis (SVA) by the Schwab-SRS classification. OUTCOME MEASURES: Radiographic spino-pelvic parameters were measured in the DLS and ASD groups, including SVA, PI-LL, T1SPi, TPA and PT. METHODS: Patients were identified using a single-institution database with sole diagnosis of DLS, >40 years and if they had any of the following: PT >25degree, SVA >5cm, thoracic kyphosis (TK) >60degree or PI-LL mismatch >10degree. The patient's diagnosis was taken from the patient history chart based on correlation between history, examination and available imaging. Matched cohort with sole diagnosis of ASD was identified. Groups were stratified by SVA using Schwab-SRS classification: 0(<4cm), +(4-9.5cm), ++( >9.5cm). Sagittal spino-pelvic parameters were compared between the 2 groups with unpaired t-test. RESULTS: 239 patients were identified (122 DLS, 117 ASD). There was no difference in age or pelvic incidence between DLS and ASD with SVA stratifications. DLS patients with SVA 0 had less PT (19.8degree vs 29.2degree p<0.0001), less PI-LL mismatch (3.3degree vs 15.8degree, p<0.001), lower TPA (14.6degree vs 21.8degree, p<0.001) but higher T1SPi (-5.17degree vs -7.44degree, p< 0.001) than those with ASD. DLS patients with SVA+ had less PT (22.6degree vs 26.1degree, p=0.019) and higher T1SPi (0.64degree vs -0.70degree, p=0.008) than ASD patients. DLS patients resembled a decompensated deformity with a higher T1SPi relative to TPA when compared to the ASD cohort in groups 0 and +. No significant differences between ASD and DLS for any parameters in the SVA++ group were identified. No difference was found between DLS or ASD in TK for SVA groups 0, + or ++. CONCLUSIONS: The difference in PI-LL observed in ASD/DLS group '0' underlies the pathogenesis of ASD vs DLS. DLS patients increase SVA for neuronal decompression but without a PI-LL mismatch, they need not increase PT. As PI-LL increases in SVA >9.5cm, recruitment of PT ensues as the need for alignment overtakes desire for decompression. Their compensatory mechanism then resembles ASD. Laminectomy 6 fusion may be more appropriate for DLS patients with SVA< 9.5cm. Given <25% of patients improve in classification after fusion, surgeons should consider realignment surgery in DLS with SVA >9.5cm. Further understanding of HRQOL scores in mal-aligned DLS patients is required to best understand the importance of alignment in DLS

BACKGROUND CONTEXT: In transforminal lumbar interbody fusion (TLIF), bilateral pedicle screw/rod fixation has been shown to increase fusion construct stability and decrease posterior instrumentation stress when compared to unilateral instrumentation. However, unilateral instrumentation is beneficial over bilateral instrumentation due to shorter operative time, less blood loss and reduced implant costs. It is important to note though that comparative studies between unilateral and bilateral instrumentation in TLIF have shown similar patient satisfaction outcomes, they are limited in their evaluation of complications due to small sample size of studies. PURPOSE: The purpose of this meta-analysis was to evaluate complications, and fusion rates between unilateral and bilateral instrumentation in TLIF. STUDY DESIGN/SETTING: Meta-analysis of randomized controlled trials. PATIENT SAMPLE: 549 patients undergoing one- and multi-levels TLIF. OUTCOME MEASURES: Outcome data extracted included fusion rates, health related quality of life (HRQoL) scores and complications including cage migration, dural tear, deep vein thrombosis, surgical site infections and screw failures. METHODS: Randomized controlled trials (RCTs) that compared outcomes between unilateral and bilateral pedicle screw instrumentation in single- and multi-level TLIF were identified. Data extraction was performed by two independent reviewers. Meta-analysis was performed using RevMan 5. Weighted standardized mean difference (SMD) and odds ratio (OR) 95% confidence intervals (CI) were calculated. Jadad scoring was used to assess bias of included studies. RESULTS: Eight RCTs were included, having a total of 549 patients (267 unilateral/282 bilateral). Minimum follow-up ranged from 3 to 24 months. Bias-assessment scores varied between 0 and 3 indicating high-moderate bias-risk. Six involved open TLIF procedures and two involved minimally invasive TLIF. There was no difference between postoperative Health Related Quality of Life scores in the unilateral and bilateral instrumented groups (SMD = 0.29; [-0.77, 0.18]; p=0.69). There was no statistical difference in fusion rates (OR = 0.47; 95% CI [0.21, 1.04], p=0.68), with 88.9% and 95.0% achieving fusion in the unilateral and bilateral groups, respectively. The unilateral cohort had a higher incidence of cage migration (5.6%) when compared to the bilateral cohort (2.5%), approaching statically significant (p=0.07). Other complications which included dural tears, deep vein thrombosis, surgical site infections and screw failures were comparable between the groups. CONCLUSIONS: Fusion rates and complications appear comparable in unilateral and bilateral instrumentation in TLIF. Though not statistically significant, there was higher incidence of cage migration in the unilateral cohort