Intraosseous Fifth Carpometacarpal Dislocation Associated with a Coronal Hamate Fracture: A Case Report.

Abstract

Fractures of the hamate are relatively uncommon, accounting for approximately 2% to 7% of all carpal bone fractures, with injuries of the hamate body being the most rare variant1,2. These injuries typically are referred to as hamatometacarpal fracture-dislocations when associated with fracture-dislocations of the fourth and/or fifth metacarpals, as is often the case3,4. The original classification system of hamatometacarpal dislocations was developed by Cain et al. and was based on the orientation of the hamate fracture line3. Coronal fractures of the hamate body were identified as type-III injuries (Table I); however, this classification system was limited by its definition that hamatometacarpal fracture-dislocation includes a fracture of the fourth metacarpal as well as a fifth carpometacarpal (CMC) injury3. Advances in diagnostic imaging have allowed for more accurate assessment of injuries to the hamatometacarpal complex, which has resulted in the development of novel classification systems. These new classification systems have focused on more specific features of these injuries, such as the presence of metacarpal base fractures and the size of the intra-articular hamate fracture fragment (Table I)4,5. View this table: TABLE I Classification Systems for Hamatometacarpal Fracture-Dislocation* Treatment options for coronal fractures of the hamate range from conservative immobilization to operative internal fixation with Kirschner wires and/or interfragmentary screw fixation. To date, treatment guidelines have largely been based on individual case reports or small case series6. Wharton et al. suggested that any displaced coronal fractures of the hamate or coronal fractures associated with metacarpal subluxation or fracture should be treated with open reduction and internal fixation to reduce the incidence of CMC subluxation6. We describe a coronal plane cleavage fracture of the hamate with intraosseous impaction of the fifth metacarpal base proximally into the hamate, …