Mechanical complications and reoperations after adult spinal deformity surgery: a clinical analysis with the GAP score

Purpose Adult spinal deformity (ASD) surgery is prone to postoperative complications, leading to high reoperation rates. The global alignment and proportion (GAP) score is a novel method to predict mechanical complications (MC) based on the optimal parameters related to individual pelvic incidence. The aim of this study was to determine the cut-off point and the predictive value of the GAP score for those MCs that require reoperation. A secondary aim was to investigate the cumulative incidence of MCs requiring reoperation during a long follow-up period. Methods In total, 144 ASD patients were operated at our institution due to marked symptomatic spinal deformity between 2008 and 2020. The cut-off point and the predictive value of the GAP score for the MCs that required reoperation and the cumulative incidence of reoperated MCs after index surgery were determined. Results A total of 142 patients were included in the analysis. The risk for having an MC that required reoperation was significantly lower when the postoperative GAP score was < 5 (HR = 3.55, 95