Ulnar nerve compression at the wrist by the accessory abductor digiti minimi muscle: wrist trauma as a precipitating factor.

This paper describes four cases of ulnar tunnel compression syndrome caused by the accessory abductor digiti minimi muscle and stresses on the observation that wrist trauma could be an important precipitating factor. Possible pathophysiological explanations of this phenomenon are offered and the anatomy of the accessory abductor digiti minimi muscle is reviewed.