A Novel Composite Frailty Score for Predicting Adverse Outcomes For Adult Women Undergoing Ankle Fracture Surgery: Model Development and Validation

Background: Ankle fracture repair is a common orthopedic procedure, but outcomes vary significantly in vulnerable populations such as smokers. Frailty and nutritional deficits contribute independently to surgical risk, yet no validated composite score exists for risk stratification in this setting. Methods: Using ACS-NSQIP data from 2015–2021, we identified 14,818 adult smokers who underwent operative fixation of isolated ankle fractures. We developed the Combined ASA–RAI–Preoperative Acute Severe Condition (CARP) score by integrating the ASA classification, Risk Analysis Index, and PACS. We evaluated predictive accuracy for major complications, readmission, extended length of stay (eLOS), and non-home discharge using AUROC analysis and bootstrap validation. Results: The CARP score outperformed individual indices across all outcomes. For major complications, CARP achieved an AUROC of 0.721 versus 0.695 (RAI) and 0.695 (mFI-5). For eLOS, CARP reached 0.783 versus 0.770 (RAI) and 0.693 (mFI-5). Bootstrap-corrected AUROCs remained consistently higher for CARP, with significant improvements shown by DeLong tests. Conclusion: The CARP score provides superior discriminatory power over existing frailty and nutritional indices in predicting postoperative risks in smokers undergoing ankle fracture repair. Its integration into preoperative planning may improve risk stratification and guide individualized care.