Electrodiagnosis of Martin-Gruber connection and its clinical importance in peripheral nerve surgery.

We propose new criteria for the electrodiagnosis of Martin-Gruber connection. Forty-seven patients with cubital tunnel syndrome were studied, and 8 (17%) were found to have a Martin-Gruber connection. Eighty-seven patients without cubital tunnel syndrome were also studied, and 14 (16%) had a Martin-Gruber connection. The rate of occurrence of the anastomosis in these two groups was approximately the same. No sensory communication was demonstrated, and the lateral intrinsic muscles received more innervation from the communicating branch than the hypothenar muscles. The entry point of the crossing fiber from the median nerve to the ulnar nerve was 3 to 10 cm distal to the medial humeral epicondyle, and there may be a significant risk of injury in ulnar nerve transposition.