The purpose of this study was to devise a novel classification of a hamatometacarpal fracture–dislocation based on the preoperative computed tomography (CT) and plain radiography that provided more information to surgeons regarding appropriate treatment methods.

Twenty-one patients with a hamatometacarpal fracture–dislocation were enrolled in this study. The classification scheme devised for hamatometacarpal fracture–dislocation is summarised as follows: type I – a simple dislocation; type IIA – a dislocation with the fourth metacarpal base intra-articular fracture; type IIB – a dislocation with a dorsal hamate fracture of less than one-third of the articular surface; and type III – a dislocation with a dorsal hamate fracture of more than one-third of the articular surface.

Type I injury was treated conservatively after closed reduction. Type IIA and IIB injuries were treated by percutaneous K-wire fixation. Type III injury was treated by open reduction and internal fixation. All injuries were well managed in both clinical and radiographic evaluations, without apparent complications.

The novel classification system for hamatometacarpal fracture–dislocation can be used to establish guidelines for appropriate treatment.