Avulsion fracture of the calcaneus at the origin of the abductor hallucis muscle.

Previously reported avulsion fractures of the calcaneus have been confined to the attachment of the tendo achillis, bifurcate ligament, extensor digitorum brevis muscle, or the plantar fascia. A case report of a previously undescribed avulsion fracture of the calcaneus due to the abductor hallucis muscle is presented. The mechanism of injury, forced dorsiflexion of the forefoot, is described. A diagnostic and treatment regimen is provided. With appropriate identification of the injury, this unusual calcaneal fracture can be adequately managed.