Lunate Dislocation

A 24-year-old man sustained a fall on his outstretched hand (FOOSH) injury that was complicated by wrist hyperextension. He complained of persistent right wrist pain and loss of grip strength.

Although the proximal and distal carpal rows are normally retained by strong volar and dorsal ligaments, Thomas A. Keel, MS, OPA, of San Antonio, Tex, writes that hyperextension can result in carpal fractures and/or ligamentous injury with associated carpal dislocation. This patient had a volar wrist bump and edema, but no fracture-related crepitus was detected.

Carpal imaging requires multiple views because the tightly packed carpus usually overlap and may obscure carpal lesions. Radiographs of this patient's wrist ruled out fracture and demonstrated a perilunate dislocation (A). The lunate normally remains fixed to the distal radius while other carpal structures shift. Carpal proximal and distal rows appear to have lost their anatomic alignment with the lunate and distal radius, which is common in FOOSH injuries with wrist hyperextension.

The second radiograph (B), a lateral view taken with right hand wrist traction, shows the tilted lunate, which accurately depicts the “spilled teacup,” or dislocated lunate, sign. Lunate dislocation is the final phase of the more common perilunate dislocation in which the lunate retains lunate/radius alignment. Here, the capitate, lunate, and distal radius are not in line; the lunate is dislocated in the volar direction and was readily palpable. No fractures were demonstrated.

The hand was neurovascularly intact. Closed reduction was performed and the wrist was immobilized.

Two radiographic examinations performed while the hand was in a cast ruled out reduction loss and the need for surgery. The patient was in a short arm cast for 4 weeks; physical therapy for hand-wrist rehabilitation followed. The injury healed without sequelae.