1536. Defining Age-Adjusted Spinopelvic Alignment Thresholds: Should We Integrate BMI?

Authors: Peter Gust Passias; Frank Segreto; Samantha Horn; Cole Bortz; Dennis Vasquez-Montes, MS; Haddy Alas; Renaud Lafage, MS; Virginie Lafage; Michael Gerling, MD; Charla Fischer, MD; Bassel Diebo, MD; Aaron Buckland, MBBS (Brooklyn Heights, NY)

Introduction: The ISSG recently developed age-adjusted alignment targets for ASD patients. While age-related changes account for significant variance among patient-reported outcomes (PROMs) and spinal alignment, the literature also indicates significant associations between BMI, spinal alignment, and PROMS. Methods: ASD patients receiving operative or nonoperative treatment, ≥18y/o with complete baseline (BL) ODI scores and radiographic parameters (PT, SVA, PILL, TPA) were included. Patients were stratified by age consistent with US-Normative values (norms) of SF-36 (<35, 35-55, 45-54, 55-64, 65-74, ≥75y/o), and dichotomized by BMI (Non Obese <30; Obese ≥30). Linear regression analysis established normative age and BMI specific radiographic thresholds, utilizing previously published age specific US-Normative ODI values converted from SF-36 PCS (Lafage et al.), in conjunction with BL age and BMI means. Results: 478 patients were included (52.53yrs, 68.7%F, 26.2kg/m2). Initial analysis identified significant correlations between age, BMI, PT, PILL, TPA, and PDI (R: 0.129-0.488, all p<0.001). Obese patients had significantly higher ODI scores compared to non-obese patients (40.6 vs 29.6, p<0.001). Linear regression analysis (all R > 0.50, p<0.001) developed age and BMI-specific alignment thresholds, with PT, SVA, PILL, TPA increasing as both age and BMI increased. For non-obese patients, PT, SVA, PILL, TPA ranged from 10.0, -25.8, -9.0, 3.1 in patients <35 y/o to 22.3, 53.4, 17.7, 25.8 in patients ≥75 y/o. Obese patients’ PT, SVA, PILL, and TPA ranged from 8.9, -7.6, -7.1, 3.1 in patients <35 y/o to 22.71, 67.0, 19.15, 27.7 in patients ≥75y/o. Normative SVA values in obese patients were consistently ≥10mm greater compared to non-obese values, at all ages. Conclusion: Significant associations exist between age, BMI, and sagittal alignment. Obesity most greatly influenced SVA, with normative values similar to non-obese patients 10 years older. Age-adjusted alignment thresholds should take BMI into account, calling for less rigorous alignment objectives in older and obese patients.