Impact of Calcaneofibular Ligament Morphology on Recurrent Instability Following Arthroscopic Anterior Lateral Ankle Ligament Repair for Chronic Ankle Instability

Background: Arthroscopic anterior talofibular ligament (ATFL) repair for chronic lateral ankle instability (CLAI) has shown favorable outcomes; however, instability recurrence has been reported. CLAI is frequently associated with concomitant calcaneofibular ligament (CFL) injury; its effects on postoperative outcomes remain unclear. This study aimed to investigate the association between preoperative magnetic resonance imaging (MRI) findings of the CFL and postoperative recurrence. Methods: This hypothesis-testing retrospective cohort study included 65 ankles in 60 patients (mean age, 34.0 ± 16.0 years) who underwent arthroscopic ATFL repair between November 2019 and June 2024. Preoperative oblique coronal MRI was used to classify the CFL morphology as intact, wavy, or thin. Clinical outcomes were assessed using the Japanese Society for Surgery of the Foot (JSSF) hindfoot-ankle scale, Karlsson- Peterson (K-P) score, and the Self-Administered Foot Evaluation Questionnaire (SAFE-Q). Recurrent ankle instability, defined as any postoperative ankle sprain during follow-up, was recorded. Multivariable analysis was performed to identify independent recurrent instability predictors. Results: Postoperative JSSF, K-P, and SAFE-Q scores improved significantly in all patients. Recurrent instability occurred in 13 of the 65 ankles (20.0%). Preoperative MRI revealed CFL injury in 38 ankles (58.5%). Additional CFL repair was performed in 24 ankles. Recurrence rates were higher in ankles with CFL injuries, particularly in those with thin (31.5%) and wavy (26.3%) morphologies. In the Firth model, CFL injury was independently associated with recurrence (OR 9.00, 95% CI 1.95-56.22, P = .004), whereas CFL repair showed a protective trend. Bootstrap analysis confirmed the significance of CFL injury. Conclusion: Preoperative MRI evaluation of CFL morphology is a significant predictor for identifying risk of postoperative recurrence after arthroscopic ATFL repair. CFL injury, particularly thin-type morphology, is associated with higher recurrence rates, suggesting the need for additional reconstructive or augmentative procedures to optimize clinical outcomes.