Perilunate injuries typically stem from a high-energy insult to the carpus. Because of their relative infrequency and often subtle radiographic and physical examination findings, these injuries are often undetected in the emergency department setting.1 Early anatomic reduction of any carpal malalignment is essential. Even with optimal treatment, complications such as generalized wrist stiffness, diminished grip strength, and posttraumatic arthritis, commonly develop; however, recent studies suggest these issues are often well tolerated.1-5 In this article, the diagnosis, treatment, and outcomes after perilunate injuries are examined.
History and Physical Examination
Perilunate injuries result from high-energy trauma to the carpus. Patients with these injuries often present with vague wrist pain and loss of wrist motion. Their fingers are frequently held in slight flexion. The patient may complain of numbness and tingling in the median nerve distribution. An acute carpal tunnel syndrome can rapidly develop. The general belief is that acute carpal tunnel syndrome occurs more commonly in pure volar lunate dislocations than in dorsal perilunate dislocations. However, no studies compare the incidence of acute carpal tunnel syndrome in lunate versus perilunate dislocations.
Radiographic Evaluation
Standard radiographic evaluation of a potential perilunate injury includes posteroanterior (PA), lateral, and oblique views of the wrist (Figure 1). A scaphoid view (ie, PA view with the wrist in ulnar deviation) may also be helpful. The PA view is particularly helpful because it enables assessment of Gilula lines, which are imaginary lines drawn across the proximal and distal aspects of the proximal carpal row and the proximal aspect of the distal carpal row. These lines should appear as 3 smooth arcs running nearly parallel to each other.6 Any disruption in these lines suggests carpal incongruity. It may be possible to note a triangular-shaped lunate on the PA view, which is a sign of lunate dislocation.7
While the PA view is certainly useful, the lateral view is the most important in diagnosing a perilunate injury. The lateral view allows assessment of the collinearity of radius, lunate, and capitate. Any disruption in this collinearity strongly suggests a perilunate dislocation.7,8
Classification
Mayfield and colleagues9,10 described 4 stages of perilunate instability proceeding from a radial to an ulnar direction around the lunate. Stage I involves disruption of the scapholunate joint, while stage II involves both the scapholunate and capitolunate joints. In stage III, the scapholunate, capitolunate, and lunotriquetral ligaments are disrupted, and the result is a perilunate dislocation, usually dorsal. Finally, in stage IV, all the ligaments surrounding the lunate are disrupted and the lunate dislocates, most often volarly.
Lastly, perilunate injuries can be classified as greater-arc injuries if concomitant fracture of the carpus occurs, lesser-arc injuries if the injury is purely ligamentous, or inferior-arc injuries if there is an associated fracture of the volar rim of the distal radius.8
Treatment
Closed Reduction
All acute perilunate dislocations should be managed initially with an attempted closed reduction.11 If the injury is older than 72 hours, such an attempt may be futile. For any closed reduction performed in the emergency department setting, intravenous sedation is generally advised for muscle relaxation. Gentle traction with finger traps can also be used prior to the reduction attempt. For a dorsal perilunate dislocation, longitudinal traction followed by volar flexion of the wrist with volar pressure on the lunate and dorsal pressure on the capitate (ie, Tavernier’s maneuver) is required. Once reduction is complete, PA and lateral views of the wrist should be obtained to assess carpal alignment. If closed reduction is unsuccessful, an open reduction is required, although the timing of said procedure is an area of debate, which we will discuss later.1,3 Restoration of anatomic carpal alignment is essential to optimizing outcome, although it does not guarantee a good overall result.
Open Reduction
If successful closed reduction is achieved, the patient can be immobilized temporarily in a short-arm plaster splint. However, open reduction and either pinning or internal fixation will be required to maintain this alignment. The exact timing of open reduction and fixation is debatable and often dictated by the absence or presence of median nerve symptoms.1,3 If a patient with no median nerve symptoms undergoes a successful closed reduction, he or she may be stabilized surgically within 3 to 5 days (or longer) with either pins or headless screws. If closed reduction is unsuccessful, an open reduction should be done within 2 to 3 days. However, if the patient has progressive numbness in the median nerve distribution upon presentation that fails to improve or worsens despite a successful closed reduction, an urgent open reduction (within 24 hours) and carpal tunnel release should be performed to prevent permanent damage to the median nerve.