A LASSO regression-driven nomogram to predict functional outcomes after surgery for chronic lateral ankle instability.

OBJECTIVE: This study aimed to identify predictors of postoperative recovery in chronic lateral ankle instability (CLAI) and construct a risk-estimation nomogram for individualized risk assessment. METHODS: Between January 2021 and December 2023, 132 patients with CLAI who underwent arthroscopic Broström repair with suture-tape augmentation were retrospectively included and classified into good-recovery [American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score ≥75, n = 73] and poor-recovery groups (AOFAS <75, n = 59). Candidate predictors were identified using univariate analysis, LASSO regression, and multivariable logistic regression. A nomogram was developed and internally validated using 1,000 bootstrap resamples, and model performance was assessed by ROC curve analysis, calibration analysis, and decision curve analysis (DCA). RESULTS: Six variables were identified as independently associated with poor postoperative recovery: sprain count (OR = 1.439, P = 0.043), osteophytes (OR = 5.951, P = 0.004), syndesmosis injury (OR = 5.272, P = 0.007), Outerbridge grade II cartilage damage (OR = 23.928, P = 0.017), thin or absent ATFL remnant <1.0 mm (OR = 5.256, P = 0.029), and CFL/ATFL angle <70° (OR = 11.598, P = 0.003). The nomogram showed acceptable discrimination, with an apparent AUC of 0.907 and an optimism-corrected AUC of 0.876 after 1,000 bootstrap resamples. Calibration demonstrated acceptable agreement between predicted and observed outcomes, and DCA suggested potential clinical utility. CONCLUSION: This study identified six variables associated with AOFAS-defined poor postoperative functional recovery in patients with CLAI and developed an internally validated nomogram for individualized risk estimation.