Comparison of the modified Broström-Gould procedure for chronic lateral ankle instability in adolescents with and without an os subfibulare : a propensity score-matched study

An os subfibulare (OS) is frequently seen in adolescents with chronic lateral instability of the ankle, potentially impairing participation in sport and the quality of life. The aim of this study was to compare the clinical outcomes of the modified Broström-Gould procedure in adolescent patients with chronic lateral instability of the ankle with and without an OS. We retrospectively reviewed adolescent patients who underwent a modified Broström-Gould procedure for chronic instability of the ankle between August 2019 and July 2023. Propensity score matching (1:1) was undertaken based on age, sex, side, BMI, the duration of symptoms, pre-injury Tegner score, and joint hypermobility, yielding 82 matched cases (41 OS and 41 non-OS). Preoperative imaging parameters and intraoperative findings were recorded. Primary outcomes included patient-reported outcome measures (PROMs): a visual analogue scale (VAS) for pain, the Karlsson score, the Tegner score, and the Foot and Ankle Outcome Score (FAOS). Secondary outcomes included the incidence of re-sprain, the time to return to sport, satisfaction, and complications. Logistic regression analysis identified risk factors for re-sprain. The mean follow-up was 47.8 months (SD 11.2) in the OS group and 47.9 months (SD 9.6) in the non-OS group (p = 0.949). Both groups had significant improvements in all PROMs, with no differences between the groups for the VAS, Karlsson score, Tegner score, or FAOS. Re-sprain occurred in five in the OS group (12.2%) and 12 in the non-OS group (29.3%) (p = 0.081). Multivariate analysis identified higher pre-injury Tegner score (p = 0.001) and concomitant calcaneofibular ligament injury (p = 0.028) as significant independent risk factors for re-sprain. In adolescent patients with chronic lateral instabilty of the ankle, the presence of an OS does not compromise the outcomes of a modified Broström-Gould procedure. Excision of the OS combined with ligamentous repair provides improvements which are comparable to those of an isolated repair, representing a safe and effective form of surgical treatment. Nonetheless, greater attention should be given to patients with high sporting demands or concomitant calcaneofibular ligament injury, due to their increased risk of re-sprain postoperatively.