Development and external validation of a decision-support model for predicting failed closed reduction in pediatric supracondylar humerus fractures: a multicenter retrospective study

Background: Closed reduction and percutaneous pinning (CRPP) is the standard treatment for pediatric supracondylar humerus fractures (SCHF). However, closed reduction can be challenging in a subset of patients and may fail, requiring conversion to open reduction. A practical preoperative tool to predict failed closed reduction remains lacking. Methods: This multicenter retrospective cohort study included pediatric patients with SCHF who underwent intended CRPP at Xiangtan Central Hospital and Zhuzhou Central Hospital between 2020 and 2025. The primary outcome was failed closed reduction, defined as intraoperative conversion to open reduction (including mini-open exposure) after attempted standard closed reduction maneuvers and before definitive K-wire fixation. Candidate predictors were selected using least absolute shrinkage and selection operator (LASSO) regression and incorporated into a multivariable logistic regression model. Model performance was assessed by discrimination, calibration, and decision curve analysis (DCA). External validation was performed using an independent cohort. Results: = 93). Conversion to open reduction occurred in 34.1% of patients. In the final multivariable model, displacement direction, preoperative Baumann angle, and the presence of a medial spike/entrapment sign were retained as predictors. The model demonstrated good discrimination in the development cohort (AUC = 0.842) and acceptable discrimination in the external validation cohort (AUC = 0.727). Calibration showed good agreement between predicted and observed risks, and decision curve analysis suggested potential clinical utility across relevant threshold probabilities. Conclusions: We developed and externally validated a practical decision-support model for predicting failed closed reduction (conversion to open reduction) in pediatric SCHF. This tool may facilitate preoperative planning and timely preparation for open reduction when needed, potentially improving operative efficiency and patient safety. However, given the retrospective design and the limited regional cohort, further prospective validation is required before routine clinical implementation.