28.1 Introduction

Perilunate injuries are highly unstable carpal dissociations, characterized by a complete loss of contact between the lunate and surrounding carpal bones. Perilunate injuries are referred to as lesser arc injuries when ligaments around the lunate are involved only, whereas dislocations associated with fractures (perilunate fracture dislocations) are referred to as greater arc injuries (▶Fig. 28.1). ¹ Greater arc injuries most commonly involve fractures through the scaphoid (trans-scaphoid perilunate fracture dislocation), accounting for approximately 95% of perilunate fracture dislocations (▶Fig. 28.2). ²

Perilunate injuries are caused by high-energy impact, such as falling from a height, motor vehicle accidents, or play injury from contact sports. The mechanism of these injuries includes forceful hyperextension, ulnar deviation, and intercarpal supination of the wrist along with axial load. The force is applied to the scaphoid (causing a trans-scaphoid fracture) or to the scapholunate ligament (causing a scapholunate dissociation). The force then progresses through the scaphocapitate and capitolunate joint or capitate, finally reaching the lunotriquetral ligament or triquetrum. Based on these pathomechanics, Mayfield et al ¹ described a spectrum of injuries characterized by four distinct stages (▶Fig. 28.3).

In Stage 1 injuries, the scapholunate ligament and the radioscapholu nate ligament are torn. In case of Stage 2 injuries, the force is transmitted to the lunocapitate articu lation where the capitate dislocates; the radioscaphocapitate ligament, dorsal intercarpal ligament, and radial collateral ligament are injured. In Stage 3 injuries, energy propagates into the lunotriquetral joint, resulting in the lunotriquetral ligament tear and a triquetral dislocation. In Stage 4 injuries, the lunate dislocates volarly and no longer remains within the lunate fossa as a result of ulnotriquetral and dorsal radiocarpal ligament tears.

The key to successful treatment of perilunate injuries is the restoration of normal alignment of the carpal bones, followed by stable maintenance until healing. ^{4 , 5} Although it is usually possible to grossly reduce the dislocation by closed manipulation, restoration of anatomic alignment of all injured structures cannot be achieved by closed means. ⁶ Complete restoration of proximal carpal bones makes good results and prevents sequelae such as nonunion, chronic instability, and arthritis. ^{7 , 8} The generally accepted treatment has been open primary repair or reconstruction of the ligaments with open reduction and internal fixation of the fractures. ^{4 , 9 , 10 , 11}

Arthroscopic treatment allows anatomic reduction of intercarpal articulations and proper reestablishment of carpal stability. ^{11 , 12 , 13} Recent arthroscopic techniques as a minimal invasive treatment have emerged with results similar to or better than those of open approach, as well as having less posttraumatic arthrosis. ^{13 , 14 , 15 , 16 , 17 , 18}

28.2 Indications

Acute dislocation failing to manual reduction and chronic dislocation without reduction necessarily require open surgery, but once the dislocation has been reduced, arthroscopic restoration of the carpal bones and percutaneous fixation are possible. The perilunate injuries are combined injury of interosseous ligaments and carpal bones fracture. Arthroscopic approach is possible for each, so that the perilunate injuries can be successfully treated with arthroscopy. ^{15 , 19} The most common form of perilunate injuries is the trans-scaphoid perilunate fracture dislocation, which is a good indication of arthroscopy surgery because the scapholunate ligament is intact. ^{5 , 20}

The feasibility of arthroscopic technique in presence of median nerve dysfunction and whether intercarpal ligaments can achieve reliable healing that is sufficient enough to maintain carpal stability without a direct repair are uncertain and debatable.