Faculty Bibliography

BACKGROUND CONTEXT: Obesity's impact on standing sagittal alignment remains poorly understood, especially with respect to the role of the lower-limbs. Given energetic expenditure in standing, a complete understanding of compensation in obese patients with sagittal malalignment remains relevant. PURPOSE: This study compares obese and non-obese patients with progressive sagittal malalignment for differences in recruitment of pelvic and lower limb mechanisms. STUDY DESIGN/SETTING: Single center retrospective review. PATIENT SAMPLE: 554 patients (277 obese, 277 non-obese) identified for analysis. OUTCOME MEASURES: Upper body alignment parameters: sagittal vertical axis (SVA) and T1 spino-pelvic inclination (T1SPi). Compensatory lower-limb mechanisms: pelvic translation (PS: pelvic shift), knee (KA) and ankle (AA) flexion, hip extension (SFA: sacrofemoral angle), and global sagittal angle (GSA). METHODS: Inclusion criteria were patients>/=18 years that underwent full body stereographic x-rays. Included patients were categorized as non-obese (N-Ob: BMI<30 kg/m2) and obese (Ob: BMI>/=30 kg/m2). To control for potential confounders, groups were propensity score matched by age, gender and baseline pelvic incidence (PI), and subsequently categorized by increasing spino-pelvic (PI-LL) mismatch: <10 degrees , 10 degrees -20 degrees , >20 degrees . Independent t-tests and linear regression models compared sagittal (SVA, T1SPi) and lower limb (PS, KA, AA, SFA, GSA) parameters between obesity cohorts. RESULTS: 554 patients (277 Ob, 277 N-Ob) were included for analysis, and were stratified to the following mismatch categories: <10 degrees : n=367; 10 degrees -20 degrees : n=91; >20 degrees : n=96. Ob patients had higher SVA, KA, PS and GSA compared to N-Ob (p<0.001 all). Low PI-LL mismatch Ob patients had greater SVA with lower SFA (142.22 degrees vs. 156.66 degrees , p=0.032), higher KA (5.22 degrees vs. 2.93 degrees , p=0.004) and PS (4.91 vs. -5.20 mm, p<0.001) compared to N-Ob. With moderate PI-LL mismatch, Ob patients similarly demonstrated greater SVA, KA, and PS, combined with significantly lower PT (23.69 degrees vs. 27.14 degrees , p=0.012). Obese patients of highest (>20 degrees ) PI-LL mismatch showed greatest forward malalignment (SVA, T1SPi) with significantly greater PS, and a concomitantly high GSA (12.86 degrees vs. 9.67 degrees , p=0.005). Regression analysis for lower-limb compensation revealed that increasing BMI and PI-LL predicted KA (r2=0.234) and GSA (r2=0.563). CONCLUSIONS: With progressive sagittal malalignment, obese patients differentially recruit lower extremity compensatory mechanisms while non-obese preferentially recruit pelvic mechanisms. The ability to compensate for progressive sagittal malalignment with the pelvic retroversion is limited by obesity.

BACKGROUND: Estimation of skeletal maturity, classically performed using Risser sign, plays a crucial role in the treatment of AIS. Recent data, however, has shown the simplified Tanner-Whitehouse (Sanders) classification, based on an anteriorposterior (AP) hand radiographs, to correlate more closely to the rapid growth phase and thus curve progression. This study evaluated the interobserver and intraobserver reliability of the Sanders and Risser classifications among clinicians at different levels of training. METHODS: Twenty AP scoliosis radiographs and 20 AP hand radiographs were randomized and distributed to 11 graders. The graders consisted of 3 orthopaedic residents, 3 spine fellows, 3 spine surgeons, and 1 radiologist. The graders were then asked to classify the radiographs according to the Sanders and Risser classifications. There were 3 rounds of grading, each done 3 weeks apart. The overall kappa coefficient was then calculated for each system to evaluate the interobserver and intraobserver reliability. RESULTS: For all graders the average kappa coefficient for the interobserver and intraobserver reliability of the Sanders classification was 0.54 and 0.62, respectively, and 0.46 and 0.49 for the Risser classification. With respect to spine attendings alone, the average kappa coefficient for the interobserver and intraobserver reliability of Sanders classification was 0.72 and 0.77, respectively, and 0.46 and 0.67 for the Risser classification. CONCLUSIONS: Our study demonstrated that the Sanders classification had moderate reliability with respect to physicians at various levels of training and had good reliability with respect to attending spine surgeons. Interestingly, the Risser staging was found to have less interobserver and intraobserver reliability overall. The Sanders classification is a reliable and reproducible system and should be in the armamentarium of surgeons who treat adolescent idiopathic scoliosis. LEVEL OF EVIDENCE: Level III.

STUDY DESIGN: Retrospective clinical and radiographic single-center study OBJECTIVE.: Assess simultaneous cervical spine and lower extremity compensatory changes with changes in thoracolumbar spinal alignment. SUMMARY OF BACKGROUND DATA: Full-body stereoradiographic imaging allows better understanding of reciprocal changes in cervical and lower extremity alignment in the setting of thoracolumbar malalignment. Few studies describe the simultaneous effect of alignment correction on these mechanisms. METHODS: Patients >/=18 years undergoing instrumented thoracolumbar fusion without previous cervical spine fusion, hip, knee or ankle arthroplasty were included. Spinopelvic, lower extremity and cervical alignment were assessed from full-body standing stereoradiographs using validated software. Patients were matched for pelvic incidence and stratified based on baseline T1-pelvic angle (TPA) as: TPA-Low <14 degrees , TPA-Moderate =14-22 degrees and TPA-High >22 degrees . Perioperative changes between baseline and first postoperative visit <6 months in lower extremity alignment (pelvic shift: P Shift, sacrofemoral angle: SFA, Knee Angle: KA, Ankle Angle: AA, global sagittal axis: GSA) and cervical alignment (C0-C2 angle, C2-slope, C2-C7 lordosis and C2-C7 SVA:cSVA) were correlated with change in magnitude of TPA and sagittal vertical axis (SVA) correction. RESULTS: After matching, 87 patients were assessed. Increasing baseline TPA severity associated with a progressive increase in all regional spinopelvic parameters except thoracic kyphosis, in addition to increased SFA, P Shift, KA, GSA, and C2-C7 lordosis. As TPA correction increased, there was a reciprocal reduction in SFA, KA, P Shift, GSA and C2-C7 lordosis. Change in SVA correlated most with change in GSA (r = 0.886), P Shift (r = 0.601), KA (r = 0.534) and C2-C7 lordosis (r = 0.467). Change in TPA correlated with change in SFA (r = 0.372) while SVA did not. CONCLUSIONS: Patients with thoracolumbar malalignment exhibit compensatory changes in cervical spine and lower extremity simultaneously in the form of cervical hyperlordosis, pelvic shift, knee flexion, and pelvic retroversion. These compensatory mechanisms resolve reciprocally in a linear fashion following optimal surgical correction. LEVEL OF EVIDENCE: 3.

STUDY DESIGN: Retrospective cohort study of a prospectively-collected surgical database. OBJECTIVE: The aim of this study was to investigate the effect of smoking on 30-day morbidity and mortality in patients undergoing surgery for adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: There is conflicting evidence regarding the impact of smoking on short-term outcomes after spinal fusion. METHODS: A retrospective review of the prospectively-collected American College of Surgeons National Surgical Quality Improvement database was performed for the years 2007-2013. Patients who underwent spinal fusion for ASD were identified. 30-day morbidity and mortality were compared between current smokers and nonsmokers. The independent effect of smoking was investigated via multivariate logistic regression analysis. RESULTS: A total of 1,368 patients met inclusion criteria and were included in this study. Of the 1,368 patients, 15.9% were smokers and 84.1% nonsmokers. The proportion of smokers who developed at least one complication was 9.7% versus 13.6% for nonsmokers (p = 0.119). Major complication rates (including 30-day mortality) were 6.5% for smokers and 8.4% for nonsmokers (p = 0.328). Current smoking status was not associated with increased odds of developing any complication (OR 0.90; 95% CI, 0.47-1.71; p = 0.752) or major complications (OR 1.32; 95% CI 0.64-2.70; p = 0.447) after multivariate analysis. CONCLUSION: Smoking was not associated with higher 30-day complications or mortality after corrective surgery for ASD in this study. However, given the negative effects of smoking on overall health and spine surgery outcomes in the long-term, smoking cessation prior to spinal fusion is still recommended. LEVEL OF EVIDENCE: 3.

STUDY DESIGN: Retrospective study of an administrative database. OBJECTIVE: The objective was to investigate the incidence, risk factors, and mortality rate of reintubation after adult spinal deformity (ASD) surgery. BACKGROUND DATA: There are limited data regarding the occurrence of reintubation after ASD surgery. MATERIALS AND METHODS: The Nationwide Inpatient Sample database from 2002 to 2011 was used to identify adult patients who underwent elective surgery for scoliosis. Patients who required reintubation were identified and compared with controls (no reintubation). A multivariable logistic regression analysis was performed to identify independent factors associated with reintubation. RESULTS: A total of 9734 patients who underwent surgery for ASD were identified, and 182 required reintubation [1.8%; 95% confidence interval (CI), 1.6%-2.1%] on average 2 days after surgery (range, 0-28 d). After multivariable analysis, the strongest independent risk factors associated with reintubation included postoperative acute respiratory failure [odds ratio (OR), 12.0; 95% CI, 8.6-16.6], sepsis (OR, 6.9; 95% CI, 3.5-13.6), and deep vein thrombosis (OR, 5.7; 95% CI, 3.0-10.9); history of chronic lung disease (OR, 1.6; 95% CI, 1.1-2.3) and fusion of 8 or more segments (OR, 1.5; 95% CI, 1.1-2.2) were also independent risk factors. Mortality rates were significantly higher in reintubated patients (7.3%) compared with that in nonreintubated patients (0.2%, P<0.001). More importantly, reintubation was an independent risk factor for inpatient mortality (OR, 9.8; 95% CI, 4.1-23.5; P<0.001). CONCLUSIONS: The reintubation rate after ASD surgery is approximately 1.8%. Patients with a history of chronic lung disease and patients undergoing fusion of 8 or more segments may be at an increased risk for reintubation; other associated factors included acute respiratory failure, sepsis, and deep vein thrombosis. Patients who required postoperative airway management after ASD surgery were 9.8 times more likely to die during their hospital stay compared with controls.

STUDY DESIGN: Retrospective cohort study OBJECTIVE.: To assess factors potentially impacting the operative approach chosen for CSM patients on a nationwide level. SUMMARY OF BACKGROUND DATA: Cervical spondylotic myelopathy (CSM) is one of the most common spinal disorders treated by spine surgeons, with operative management consisting of three approaches: anterior-only, posterior-only, or combined anterior-posterior. It is unknown whether the operative approach used differs based on patient demographics and/or insurance status. METHODS: The Nationwide Inpatient Sample from 2001-2010 was used for analysis. Admissions having a diagnosis code of 721.1 and a primary procedure code of 81.02/81.03, 81.32/81.33, 81.02/81.03 or 81.32/81.33 (combined anterior and posterior fusion/refusion at C2 or below), and 3.09 (decompression of the spinal canal including laminoplasty) were included. Analysis was adjusted for several variables including patient age, race, sex, primary payer for care, and admission source/type. RESULTS: Multivariate analyses revealed that non-Caucasian race [Black (OR = 1.39;95%CI = 1.32-1.47;p < 0.0001), Hispanic (OR = 1.51;95%CI = 1.38-1.66;p < 0.0001), Asian/Pacific Islander (OR = 1.40;95%CI = 1.15-1.70;p = 0.0007), Native American (OR = 1.33;95%CI = 1.02-1.73;p = 0.037)] and increasing age (OR = 1.03; p < 0.0001) were predictive of receiving posterior-only approaches. Female sex (OR = 1.39;95%CI = 1.34-1.43;p < 0.0001), private insurance (OR = 1.19;95%CI = 1.14-1.25;p < 0.0001), and non-trauma center admission type (OR = 1.29-1.39;95%CI = 1.16-1.56;p < 0.0001) were independently predictive of increased likelihood of receiving an anterior-only approach. Hispanic race (OR = 1.35;95%CI = 1.14-1.59;p = 0.0004) and admission source [another hospital (OR = 1.65;95%CI = 1.20-2.27;p = 0.0023), other health facility (OR = 1.68;95%CI = 1.13-2.51;p = 0.011)] were the only variables predictive of increased combined anterior-posterior approaches; Native American race (OR = 0.32;95%CI = 0.13-0.78;p = 0.013) decreased the likelihood of a combined anterior-posterior approach. CONCLUSIONS: Private insurance status, female sex, and Caucasian race independently predict receipt of anterior-only CSM approaches, while non-Caucasian race (Black, Hispanic, Asian/Pacific Islander, Native American) and non-private insurance predict receiving posterior-only CSM approaches. Given recent literature demonstrating posterior-only approaches as predictive of increased mortality in CSM (Kaye et al., 2015), our findings indicate that for CSM patients, non-Caucasian race may significantly increase mortality risk, while private insurance status may significantly decrease the risk of mortality. Further prospective study will be needed to more definitively address these issues. LEVEL OF EVIDENCE: 3.