ISOLATED PARALYSIS OF THE EXTENSOR DIGITORUM COMMUNIS ASSOCIATED WITHTHE POSTERIOR (THOMPSON) APPROACH TO THE PROXIMAL RADIUS

Seven patients presented with an isolated extensor digitorum communis (EDC) palsy immediately after undergoing surgery in which the posterio r (Thompson) approach to the proximal radius was used. All had normal neurologic examination findings documented prior to surgery. In an att empt to localize this lesion, the authors studied the arborization of the terminal motor branches of the posterior interosseous nerve (PIN) at the distal edge of the supinator. A common innervation pattern to t he superficial extensor muscles was observed in 29 of 30 cadaveric lim bs. In 10 of 10 specimens, when the EDC was subdivided into its indivi dual bellies, a reproducible pattern emerged: the proximal EDC muscles of the middle and ring fingers were supplied primarily by the recurre nt nerve branch(es) and the EDC muscles of the index and little finger s, by separate nerve branches. Consistent with our anatomic findings, perioperative stimulation of the recurrent branch in 1 neurologically intact patient resulted in middle and ring finger extension. Electromy ography in 8 normal limbs showed that the middle and ring fingers coul d be activated together without the index and little fingers in all ca ses. We believe that these patients with isolated EDC nerve palsy may have sustained an iatrogenic injury to EDC motor branches, distal to t he supinator rather than to a PIN fascicle near the proximal supinator . Copyright (C) 1998 by the American Society for Surgery of the Hand.