Background Avulsion fracture of the extensor carpi ulnaris (ECU) bony insertion at fifth metacarpal base is a rare injury that may preclude recognition on radiographs.

Case Description We report two cases of ECU avulsion fracture, both of which were successfully treated surgically by open reduction and fixation (ORIF).

Literature Review Only two cases of ECU avulsion fracture have previously been reported in the literature. Forced motion of the wrist into a position of hyperflexion and/or radial deviation appears to be a common mechanism.

Clinical Relevance Clinicians should be aware that ECU avulsion fractures can occur in isolation or in association with other fractures of the hand or wrist. ORIF is warranted due to the prospect of impaired wrist range of motion as well as persistent pain caused by the avulsed fragment.