Median-nerve neuropathy associated with chronic anterior dislocation of the lunate.

Ten patients who had median-nerve neuropathy in association with chronic anterior dislocation of the lunate were managed operatively and were followed for an average of five years (range, three to eight years). The average time from the injury to the initial evaluation was twenty-one months (range, six to sixty-five months). All ten patients had pain as well as sensory and motor dysfunction in the distribution on the median nerve. Nerve-conduction-velocity studies revealed a delay in distal motor and sensory latencies in all patients; the distal motor latency averaged 12.5 milliseconds (range 5.6 to 18.6 milliseconds), and the distal sensory latency averaged 12.4 milliseconds (range, 4.8 to 16.8 milliseconds). Three patients had had a failed carpal tunnel release and needed excision of the lunate for decompression of the median nerve. In the other seven patients, three distinctive sites of nerve compression were identified: the volar and dorsal edges of the lunate and the proximal edge of the transverse carpal ligament. Excision of the osseous protuberance (excision of the lunate in three patients and a proximal-row carpectomy in four), combined with a release of the transverse carpal ligament, resulted in relief of the symptoms, functional improvement, and sensory and motor recovery in the distribution of the median nerve.