Perilunate Dislocation

Excerpt

Perilunate dislocations (PLDs), lunate dislocations (LDs), and perilunate fracture-dislocations (PLFDs) are rare high-energy injuries constituting less than 10% of all wrist injuries. The carpus consists of two rows of bones: proximal and distal. The proximal row, which is the more mobile of the two, articulates with the distal radius and moves in concert with the distal radius and ulna. The scaphoid, lunate, and triquetrum serve as the connecting bones that make up the proximal row. The more rigid distal row—which contains the trapezium, trapezoid, capitate, and hamate serves as a bridge between the proximal row and metacarpal bases. The carpus’ stability is maintained through its bony articulations and intrinsic and extrinsic ligaments. As its name suggests, the lunate is a semilunar bone with a crescent shape. Its proximal end is convex and articulates with the concave lunate facet of the distal radius. The distal articular surface is concave and articulates with the capitate. Bordered by the scaphoid radially and the triquetrum to its ulnar border, the lunate is attached to the scaphoid and triquetrum by the intrinsic scapholunate and lunotriquetral ligaments, respectively. Palmar attachments include the radiolunotriquetral, radioscapholunate, and ulnolunate extrinsic ligaments. The lunate serves as a center keystone and link between the forearm and the hand.

In general, PLDs occur through injuries to the surrounding stabilizing structures, such as through fractures and disruptions in articulations or ligaments. The surrounding carpal bones most commonly dislocate dorsally, and the lunate maintains its articulated position with the distal radius. Alternatively, albeit rarely, the lunate can dislocate in the volar direction into the space of Poirier. Because these injuries have the potential to cause lifelong disability of the wrist, early recognition and diagnosis are prudent to restore patient function and prevent morbidity. Early treatment may prevent or lessen the chance of median neuropathy, post-traumatic wrist arthrosis, chronic instability, and fracture nonunion. Nonoperative treatment is rarely indicated and is associated with poor functional outcomes and recurrent dislocation.