Assessing the predictive power of the GAP score on mechanical complications: a comprehensive systematic review and meta-analysis

Abstract

Abstract Purpose The prevention of mechanical complications (MC) is a major concern in adult spinal deformity (ASD) correction surgery; thus, the global alignment and proportion (GAP) score was developed to assess MC risk. Numerous studies have clarified the validity of the GAP score, but their contradictory results have prevented researchers from reaching compelling conclusions. This study aimed to analyze the predictive power of the GAP score on MC via a meta-analysis. Methods A total of 1,617 patients were included in the meta-analysis. Studies relevant to the GAP score and MC were identified in PubMed, EMBASE, and Cochrane CENTRAL and screened according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The GAP score categories of the patients and their MC/revision surgery status were collected. The data collected for the meta-analysis of odds ratios (OR) included the number of patients in the GAP score subgroups and their MC/revision surgery status. To calculate the OR, three GAP score subgroups were combined into two groups; hence, the analysis was conducted twice (gap proportioned [GAP-P] and higher groups, and gap severely disproportioned [GAP-SD] and lower groups). Results Eleven studies were collected; of them, revision surgery data were available for seven. The proportion of MC in the studies was 27.7–60.6%, while that of revision surgery was 11.7–34.9%. In the meta-analysis of the GAP-P and higher score groups, the difference in MC ratio was significant (OR = 2.83; 95% confidence interval [CI] = 1.20–6.67; P = 0.02), whereas that for revision surgery was not. For the GAP-SD and lower score groups, the GAP-SD group had significantly higher proportions of both MC (OR = 2.65; 95% CI = 1.57–4.45; P < 0.001) and revision surgery (OR = 2.27; 95% CI = 1.33–3.88; P = 0.003). Publication bias was significant only in the latter MC analysis. Conclusion The GAP score offers predictive value for the risk of mechanical complications.