• Dae-Woong Ham, Ho-Joong Kim, Jae Heouk Choi, Jiwon Park, Junpyo Lee, and Jin S Yeom.
• Spine Center and Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, Republic of Korea.
• Eur Spine J. 2021 May 1; 30 (5): 1190-1198.

PurposeThis study aimed to validate the usefulness of the global alignment proportion (GAP) score to predict postoperative mechanical failure in the elderly (mean age, 70.5 years) individuals with severe sagittal imbalance.MethodsA total of 84 patients were enrolled: mechanical complications (MC), minor mechanical complications (mMC), proximal junctional failure (PJF), and revision surgery occurred in 61% (51/84), 58% (49/84), 44% (37/84), and 13% (11/84) of the patients, respectively. The GAP score was calculated using the X-ray obtained in the early postoperative period. The validity of the GAP score's predictive ability was evaluated by calculating the area under the curve (AUC) of the receiver operating characteristics curve. Univariate logistic regression analysis and Cochran-Armitage test of trend were performed to determine the association between mechanical complications and GAP score.ResultsThe discriminatory power of GAP score to predict MC, mMC, and PJF was "moderately accurate," with an AUC of 0.839 (confidence interval [CI] 0.755-0.824, p < 0.001), 0.836 (CI 0.749-0.923, p < 0.001), and 0.702 (CI 0.588-0.851, p < 0.001), respectively. The GAP score showed a statistically significant association with MC, mMC, and PJF in univariate logistic regression analysis and Cochran-Armitage test for trend. However, it was not significantly associated with revision surgery.ConclusionThis study showed promising results regarding the GAP score's predictive power for MC, mMC, and PJF in the elderly population with degenerative kyphoscoliosis. Using the GAP score, we can determine the patient's specific correction goal preoperatively to prevent mechanical failure based on individual patient's characteristics such as pelvic incidence.

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