Ulnar styloid fractures associated with distal radius fractures: incidence and implications for distal radioulnar joint instability.

Ulnar-sided injuries of the wrist have received more attention recently for their potential negative impact on the outcome of distal radius fractures. Radiographs and medical records were retrospectively reviewed for 166 distal radius fractures treated during a 1-year interval. Distal radius fractures were classified according to the AO system, and accompanying ulnar styloid fractures were evaluated for both size and displacement. Each distal radius fracture was also evaluated for radiographic and clinical evidence of distal radioulnar joint instability. The distribution of ulnar styloid fractures was not random; greater than one third involved the base. All distal radius fractures complicated by distal radioulnar joint instability were accompanied by an ulnar styloid fracture. A fracture at the ulnar styloid's base and significant displacement of an ulnar styloid fracture were found to increase the risk of distal radioulnar joint instability.