277 - The Impact of Obesity on Compensatory Mechanisms in Response to Progre...

Oral Posters: Adult Spinal Deformity

Presented by: S. Horn - View Audio/Video Presentation (Members Only)

Author(s):

C. Jalai(1), B. Diebo(2), D. Cruz(1), G. Poorman(1), S. Vira(1), S. Horn(1), J. Moon(1), B. Beaubrun(1), A. Buckland(1), R. Lafage(3), S. Bess(4), T. Errico(1), V. Lafage(3), P. Passias(1)

(1) NYU Hospital for Joint Diseases, Orthopaedic Surgery, New York, NY, United States
(2) SUNY Downstate, Orthopaedic Surgery, New York, NY, United States
(3) Hospital for Special Surgery, New York, NY, United States
(4) Denver International Spine Center, Denver, CO, United States

Abstract

Background: 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°, 10°-20°, >20°. 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°: n=367; 10°-20°: n=91; >20°: 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° vs. 156.66°, p=0.032), higher KA (5.22° vs. 2.93°, 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° vs. 27.14°, p=0.012). Obese patients of highest (>20°) PI-LL mismatch showed greatest forward malalignment (SVA, T1SPi) with significantly greater PS, and a concomitantly high GSA (12.86° vs. 9.67°, 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.