Surgical treatment of ankle instability in children with os subfibulare

Ankle instability in children due to soft tissue injury usually resolves after non-operative treatment. However, some children and adolescents with chronic instability require surgical treatment. A rarer cause of developing ankle instability is injury to the ligament complex in the presence of os subfibulare, an accessory bone inferior to the lateral malleolus. The aim of this study was to assess the results of operative management of chronic ankle instability in children with os subfibulare.

16 children with os subfibulare and chronic ankle instability who failed non-operative treatment were enrolled prospectively into the study. One child was lost to follow-up and excluded from analysis. The mean age at the time of the surgery was 14 years and 2 months (range 9.5-17 years). The mean follow-up time was 43.2 months (range 28-48 months). Surgical treatment in all cases involved removal of os subfibulare and a modified Broström-Gould lateral complex reconstruction with anchors. Ankle status was assessed before and after surgery with The 100 mm Visual Analogue Scale and Foot and Ankle Outcome Score questionnaire.

The mean Foot and Ankle Outcome Score improved from 66.8 to 92.3 (p < 0.001). Pain level improved from 67.1 preoperatively to 12.7 (p < 0.001). All children reported improvement in their ankle stability. There was one case of scar hypersensitivity that improved during observation and one superficial wound infection that resolved with oral antibiotics. One child reported intermittent pain without symptoms of instability following another injury.

Ankle joint sprain with associated injury to os subfibulare complex can lead to chronic instability in children. If conservative management fails, then surgical treatment with modified Broström-Gould technique and excision of accessory bone is a safe and reliable method.