Review Question - QID 211798

Perilunate injuries are difficult to diagnose and are missed in up to 25% of cases. Close scrutiny of radiographs is critical to identifying the injury pattern.

As many as one-quarter of cases are missed initially, prompt recognition of perilunate injuries is critical. Radiographs should be scrutinized for perilunate injuries. On the AP there will be a break in Gilula's arcs, which are normal smooth articulations of the radiocarpal and midcarpal joint. Additionally, the lunate and capitate will abnormally overlap and the lunate will have a triangular appearance. On the lateral, the lunate will be completely volar to the capitate and the rest of the carpus. Once diagnosed, a closed reduction should be attempted, particularly if the patient has acute carpal tunnel syndrome (ACTS). The reduction is obtained typically by extending the wrist, applying axial traction, and then flexing the wrist while applying dorsal pressure over the carpus. Surgical management requires an open CTR in the setting of ACTS, followed by an open reduction, stabilization with pins, and SL ligament repair.

Budoff reviews the treatment of acute lunate and perilunate dislocations and underscores the devastating nature of these injuries. The author notes that closed reduction should be completed immediately upon presentation to relieve the pressure of the lunate on the median nerve, and if the reduction is successful, surgery can be delayed 4 days until the swelling subsides. He discusses that median nerve dysfunction is typically static and non-progressive due to swelling and hemorrhage within the carpal tunnel and does not mandate emergent release. However, he notes that delayed onset or progressive worsening of carpal tunnel syndrome is an indication for emergent carpal tunnel release combined with open reduction and carpus stabilization.

Dunn et al. reviewed 40 perilunate dislocations in a military population. They noted that over one-quarter (27.5%) were missed initially. Furthermore, one-half (50%) presented with ACTS, and 17.5% had persistent paresthesias. The authors cautioned that a high-demand patient population may experience inferior functional results due to a greater degree of postoperative limitation.

Muppavarapu et al. reviewed perilunate dislocations and fracture-dislocations, which occur when an axial load is placed upon a hyperextended and ulnarly deviated wrist. These injuries require urgent reduction followed by anatomic stabilization and ligament repair. Surgeons should be prepared to make both dorsal and volar incisions.

Figure A is an AP radiograph demonstrating a lunate dislocation. Note the triangular shape of the lunate, disruption of natural arcs within the wrist, with the lunate out of plane in comparison to the capitate and triquetrum.
Figure B is a lateral radiograph demonstrating a lunate dislocation. Note the lunate volar to the carpus.

Incorrect answers:
Answer 1: Between 25-50% of perilunate injuries present with acute carpal tunnel syndrome. A neurological exam should be performed before and after the reduction of a perilunate dislocation.
Answer 2: The short radiolunate ligament is not typically injured in this injury pattern.
Answer 3: A MRI does not contribute to understanding the diagnosis in perilunate injuries.
Answer 4: The Space of Poirier is between the radioscaphocapitate and volar long radiolunate ligaments.