Opportunistic chest CT assessment of skeletal muscle status for predicting functional recovery following medial opening wedge high tibial osteotomy: an exploratory study

Background Routine preoperative chest computed tomography (CT) provides an opportunity for opportunistic assessment of skeletal muscle status without additional imaging. This study aimed to investigate the association between chest CT-derived skeletal muscle status and postoperative functional recovery after medial opening wedge high tibial osteotomy (MOWHTO). Methods This retrospective cohort study included patients undergoing MOWHTO between January 2022 and December 2024. Skeletal muscle index (SMI) was measured from routine preoperative chest CT images at the T12 vertebral level, and CT-defined low T12 SMI was classified using sex-specific cut-off values. Postoperative Hospital for Special Surgery (HSS) scores were analyzed as both continuous and dichotomous outcomes. Multivariable Firth logistic regression was used to identify independent predictors of poor postoperative functional outcome and develop an exploratory prediction model. Model performance was assessed using receiver operating characteristic (ROC) analysis, calibration curves, and decision curve analysis (DCA). Linear regression and Spearman correlation analyses were performed to evaluate the association between skeletal muscle status and postoperative HSS scores. Results Among 183 included patients, 35 (19.1%) experienced poor postoperative functional outcomes. Multivariable Firth logistic regression identified age, diabetes, and CT-defined low T12 SMI as independent predictors. The exploratory prediction model showed good discrimination (AUC = 0.815, 95% CI: 0.738–0.893), satisfactory calibration, and favorable clinical utility. Linear regression demonstrated that age, diabetes, and CT-defined low T12 SMI were independently associated with postoperative HSS scores. Preoperative SMI showed good discrimination for poor functional outcomes in the overall cohort (AUC = 0.765, 95% CI: 0.661–0.869) and in women (AUC = 0.898, 95% CI: 0.838–0.957). Significant positive correlations were observed between SMI and postoperative HSS scores in the overall cohort and sex-specific subgroups. Conclusion Preoperative chest CT-derived skeletal muscle status was independently associated with functional recovery after MOWHTO. CT-defined low T12 SMI may serve as a practical imaging marker for preoperative risk stratification, while SMI provides complementary information regarding postoperative functional outcomes.