Comparison of Global Alignment and Proportion (GAP) Score and SRS-Schwab ASD Classification in the Analysis of Surgical Outcomes for Adult Spinal Deformity.

Study design: The GAP score predicted post-operative mechanical complications more effectively whereas SRS-Schwab classification improved evaluation of postoperative PROMs. Objective: The study compared the GAP Score and SRS-Schwab Classification in predicting surgical outcomes for adult spinal deformity (ASD) and elucidated whether both systems should be included in the preoperative planning. Materials and methods: Radiographic measurements and health-related quality of life scores at baseline, 6 weeks after surgery, and the last follow-up were collected from a cohort of 69 ASD patients subjected to long segment spinal fusion surgery after they were grouped by GAP score and SRS-Schwab classification respectively. Fisher's exact test and receiver operator characteristic (ROC) curve analysis was used to compare the incidence of mechanical complications and the discriminant capacity during revision surgery between the two groups. Postoperative patient-reported outcomes measures (PROMs) were compared by one-way ANOVA, and the proportions of MCID achieved for PROMs compared by chi-square test between the two groups. Results: The overall incidence of mechanical complications and revision surgery were 42% and 8.7%. Both GAP score and its categories predicted mechanical complications and revision surgery, but the GAP score system could not predict the improvements of PROMs. The SRS-Schwab classification could predict the occurrence of postoperative mechanical complications and improvements of postoperative PROMs between the aligned, moderately misaligned and severely misaligned groups (P < 0.05). Conclusion: Hence, a comprehensive surgical strategy for postoperative planning may improve patients' quality of life and minimize mechanical complications. Graphical Abstract: