Review Question - QID 217929

This patient has sustained a lunate dislocation, and the order of injury is classically: injury to the scapholunate ligament followed by the capitolunate ligament, lunotriquetral ligament and dorsal radiocarpal ligament.

Lunate and perilunate dislocations are complex injuries that can have catastrophic effects on patients if not managed correctly. They are typically high-energy injuries and occur with the wrist extended and ulnarly deviated. The Mayfield classification represents the common sequence of ligamentous injury, as detailed above. Scapholunate injury occurs first, followed by disruption of the capitolunate joint, then the lunotriquetral joint. Once the lunotriquetral joint is no longer congruent, a perilunate dislocation has occurred, meaning that the lunate is still articulating with the radius. Once the radiocarpal ligament is disrupted, the lunate rotates and dislocates, usually volarly which can cause acute carpal tunnel syndrome. Timely reduction is necessary and surgical fixation/ligament repair is indicated in nearly all patients.

Budoff reviewed the treatment of acute lunate and perilunate dislocations, noting they are uncommon, but devastating injuries. He discusses, at length the defining bony and ligamentous anatomy and explains the forces which cause ligamentous disruption and subsequent dislocation. Further, he reviews the acute and definitive management as well as the outcomes, for which he notes the prognosis is typically guarded.

Muppavarapu et al. also reviewed the treatment of perilunate/lunate dislocations as well as associated fractures. They highlight the high rate of incorrect diagnoses in these cases and discuss methods for recognizing/managing these injuries acutely. They finish by noting that there is little role for closed management and the restoration of carpal alignment and ligamentous function is integral to a good outcome.

Figure A is a lateral wrist radiograph demonstrating a volar lunate dislocation. Illustration A is a lateral wrist radiograph demonstrating a perilunate dislocation. Illustration B is a table showing the Mayfield classification of perilunate and lunate dislocations based on the order of ligamentous disruption.

Incorrect Answers:
Answers 1-3,5: The correct sequence of lunate dislocation is scapholunate ligament -> capitolunate ligament -> lunotriquetral ligament -> dorsal radiocarpal ligament.