We report five examples of a triquetral fracture pattern not previously described to our knowledge. These fractures from the volar aspect of the triquetral bone are important because they are easily missed with conventional wrist radiographs and yet are associated with significant ligament injuries and carpal instability.

Five volar triquetral avulsion fractures occurred in young men (20-28 years old) during falls while playing sports. The initial evaluation consisted of a three-view radiographic series. Subsequently, an instability series was obtained in each case. Four patients were also evaluated by stress videofluoroscopy and arthrography, one by CT, and four by MR imaging.

None of the five fractures was recognized on radiographs obtained in the emergency room. Each fracture was identified on an instability series and involved the radial aspect of the volar surface of the triquetral bone. All four wrists evaluated by stress videofluoroscopy showed lunatotriquetral joint instability. One also showed instability of the scapholunate joint. All four wrists evaluated by arthrography showed tears of the lunatotriquetral ligament and three had an associated tear of the scapholunate ligament. MR examination of four wrists showed a volar capsular ligament attached to the avulsion fracture fragment in each wrist. Two of the patients were treated by arthroscopic debridement and three were treated by prolonged splinting. All five patients had persistent pain and carpal instability of variable severity at least 1 year after injury.

This avulsion fracture of the radial aspect of the volar triquetral bone is a subtle, easily missed sign of a significant injury of the perilunate ligaments. When this fracture is identified, we recommend further evaluation for associated ligament injury and carpal instability.