Chronic symptomatic os subfibulare in children.

BACKGROUND: Some children have persistent pain and instability following inversion injuries of the ankle. Radiographs may reveal a small osseous fragment distal to the lateral malleolus, suggesting an avulsion injury of the anterior talofibular ligament and/or calcaneofibular ligament. The avulsion injury may involve an os subfibulare, causing ligamentous laxity and chronic pain resulting from nonunion. This situation must be differentiated from an asymptomatic os subfibulare, which is a normal anatomic variant in 1% of children. The purpose of this study was to evaluate the intraoperative findings and long-term outcomes of patients treated operatively for symptomatic avulsion injuries or a symptomatic os subfibulare.

METHODS: Twenty-three patients presented with chronic ankle pain and instability, tenderness anterior and distal to the lateral malleolus, and imaging studies (magnetic resonance imaging and/or stress radiographs) suspicious for avulsion injury of the anterior talofibular ligament and/or calcaneofibular ligament. After unsuccessful nonoperative treatment, all patients underwent excision of the osseous fragments, anatomic reconstruction of the anterior talofibular ligament with use of drill holes through the lateral malleolus, and a modified Broström procedure.

RESULTS: The mean age of the patients was 10.4 years (range, eight to thirteen years) at the time of injury and 13.6 years (range, eight to seventeen years) at the time of surgery, representing a mean delay in diagnosis and treatment of 3.2 years. At a mean follow-up of 4.5 years (range, 2.1 to 13.2 years), the mean Foot and Ankle Outcome Score was 91.4 (range, 87 to 98) out of 100, with all but one patient returning to the preinjury recreational level. Only one patient had a long-term complication.

CONCLUSIONS: In children with chronic pain and instability associated with an os subfibulare, surgical excision of the os subfibulare combined with reconstruction of the anterior talofibular ligament and a modified Broström procedure was effective in restoring ankle stability, eliminating pain, and permitting return to the preinjury functional level.