[Wartenberg's Sign of Ulnar Nerve Lesion. A Contribution to Pathophysiology and to the Differential Diagnosis].

The abduction stance of the small finger is frequently, but not necessarily due to ulnar nerve paresis. Five cases suffering from bothersome permanent abduction of the small finger and referred under the diagnosis of ulnar nerve paresis are presented. Clinical, electrodiagnostic and imaging evaluation revealed different causes. While partial paresis with the function of the abductor digiti minimi muscle preserved usually results in a disturbing abduction stance, complete paresis of the ulnar nerve causes a less severe abduction posture of the small finger. Operative measures are indicated when the stance of the small finger is disturbing and when sufficient time has passed to make sure that spontaneous recovery cannot be presumed. Clinical, electrodiagnostic and imaging evaluation of three neurogenic cases disclosed a lesion of the ramus profundus distal to the branches innervating hypothenar muscles in one case, ulnar nerve injury with neuromuscular hyperactivity of the abductor digiti minimi muscle following split repair in another case and syringomyelia in the third case. Two patients revealed an abduction posture of the little finger of non-neurogenic origin. One of them showed closed ligament injuries. The other patient revealed necrosis, scarring and contracture of hypothenar muscles and atrophy of the third palmar interosseous muscle following compression in a tight cast.