Factors Influencing Maintenance of Alignment and Functional Improvement Following Adult Spinal Deformity Surgery: A 3-Year Outcome Analysis.

Abstract

Retrospective review. To assess the factors contributing to durability of surgical results following adult spinal deformity surgery. Factors contributing to the long-term sustainability of ASD correction are currently undefined. Operative ASD patients with preop(BL) and 3-year(3Y) postop radiographic/HRQL data were included. At 1Y and 3Y postop, a favorable outcome was defined as meeting at least 3 of 4 criteria: 1) no PJF or mechanical failure with reoperation, 2) best clinical outcome for SRS[≥4.5] or ODI[<15], 3) improving in at least one SRS-Schwab modifier, and 4) not worsening in any SRS-Schwab modifier. A robust surgical result was defined as having a favorable outcome at both 1Y and 3Y. Predictors of robust outcomes were identified using multivariable regression analysis, with conditional inference tree (CIT) for continuous variables. We included 157 ASD patients in this analysis. At 1Y postop, 62 patients (39.5%) met the best clinical outcome [BCO] definition for ODI and 33 (21.0%) met the BCO for SRS. At 3Y, 58 patients (36.9%) had BCO for ODI and 29 (18.5%) for SRS. 95 patients (60.5%) were identified as having a favorable outcome at 1Y postop. At 3Y, 85 patients (54.1%) had a favorable outcome. Seventy-eight (49.7%) patients met criteria for a durable surgical result. Multivariable adjusted analysis identified the following independent predictors of surgical durability: surgical invasiveness >65, being fused to S1/pelvis, baseline to 6 week PI-LL difference >13.9°, and having a proportional Global Alignment and Proportion (GAP) score at 6 weeks. Nearly 50% of the ASD cohort demonstrated good surgical durability, with favorable radiographic alignment and functional status maintained up to 3 years. Surgical durability was more likely in patients whose reconstruction was fused to the pelvis and addressed lumbopelvic mismatch with adequate surgical invasiveness to achieve full alignment correction.