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Global Alignment and Proportion (GAP) Score in Predicting Mechanical Complications After Long-Segment Fixation for
Xiangyao Sun1,2,3, Jiang Huang1,2, Yuqi Liu1,2
1Department of Orthopaedics, Xuanwu Hospital Capital Medical University, Beijing, China.
Objectives:
The predictive value of the global alignment and proportion (GAP) score in the Chinese geriatric population, which has unique demographic and degenerative characteristics, has not been validated. Given the high incidence of mechanical complications in this specific cohort, a dedicated mid-term evaluation is essential to guide surgical planning. To address this gap, this study aimed to analyze the accuracy and characteristics of the GAP assessment system in predicting mechanical complications following long-segment fixation surgery for geriatric patients with adult degenerative scoliosis (ADS) in a mid-term follow up period.
Methods:
A retrospective analysis was conducted to select eligible ADS patients who had undergone long-segment fixation surgery at Xuanwu Hospital Capital Medical University between December 2016 and October 2020. Patients were divided into groups with mechanical complications (MC) and nonmechanical complications (NMC) for comparison. The GAP score and its classification were calculated based on the measurements. The association between GAP scores and mechanical complications was examined using logistic regression analysis. Additionally, the receiver operating characteristic curve (ROC) was utilized to evaluate the predictive performance of the GAP score for mechanical complications and to determine the threshold of the assessment system.
Results:
A total of 133 ADS patients were included, with 65 in the MC group and 68 in the NMC group. The GAP score (area under the curve, AUC = 0.654) outperformed the GAP categories (AUC = 0.650) in predicting mechanical complications, and it was particularly accurate for proximal junctional kyphosis (PJK) (AUC = 0.872). However, both the GAP score (AUC = 0.201) and GAP categories (AUC = 0.181) demonstrated poor accuracy in predicting internal fixation breakage.
Conclusion:
The GAP score varied in its predictive performance and thresholds for different mechanical complications and internal fixation-related issues, exhibiting high accuracy for predicting PJK. However, it did not effectively indicate the risk of internal fixation breakage.