Bilateral os subtibiale and talocalcaneal coalitions in a college soccer player: a case report

An os subtibiale is an accessory bone separated from the distal medial tibia proper. Subtalar tarsal coalition is a failure of joint formation between the talus and calcaneus during hindfoot maturation. The patient in this case report has large bilateral os subtibiale and subtalar coalitions, which were undiagnosed throughout his soccer career until recently when he began having anteriorlateral ankle pain. After failing conservative treatment the patient underwent ankle arthroscopy, which revealed a fully separated, large articular portion of the medial malleolus. The hypertrophic synovium and cartilage were debrided and the patient had a full recovery, returning to soccer 8 weeks after surgery. Os subtibiale is a rare but well-described entity in the radiology and orthopaedic liturature. To our knowledge, bilateral os subtibiale this large has not been described. In addition, an os subtibiale with concomitant subtalar coalition has never been reported. This report will hopefully alert clinicians about these 2 rare anatomic findings and encourage them to use caution when evaluating suspected fractures of the medial malleolus that could be functional os subtibiale ossicles. In addition, we hope to shed some light on the complicated coupling of motion between the ankle and subtalar joint. These may have developed together to allow more normal coupled motion between the ankle and subtalar joint in this high-level college soccer player, and may be relevant to future reports or research in this area.