Modified global alignment and proportion scoring with body mass index and bone mineral density analysis in global alignment and proportion score of each 3 categories for predicting mechanical complications after adult spinal deformity surgery

Abstract

Objective: This study aimed to analyze the prediction rate of the modified Global Alignment and Proportion (GAP) scoring system with body mass index and bone mineral density (GAPB) in each GAP of the 3 categories. Methods: Between January 2009 and December 2016, 203 consecutive patients with adult spinal deformity (ASD) underwent corrective fusion of more than 4 levels and were followed-up for more than 2 years. As a validation of the GAPB, the GAPB was divided into tertiles (Q1, Q2, Q3) for each section of the GAP score. Each patient’s GAP score and GAPB system complication rate were examined. Results: Of the 203 patients, 89 patients (44%) developed mechanical complications after ASD surgery. A GAP score analysis of the patients found that 42 patients were proportioned, 85 patients were moderately disproportioned, and 76 patients were severely disproportioned. Mechanical complications occurred with increasing GAPB in the proportioned group, but were not statistically significant (p = 0.0534). However, mechanical complications occurred in a statistically significant manner in the moderately disproportioned and severely disproportioned groups as GAPB increased (p < 0.001). Conclusion: The GAPB system showed improved predictability for mechanical complications after surgery for ASD in each category of the GAP score.