[Muscle abnormalities on the back of the hand and their differentiation from soft-tissue tumors].

Anomalous muscles at the hand and forearm are described in several studies. They may be confused with ganglia or with other soft-tissue tumours. Two rare cases of atavistic muscles in the area of the back of the hand are described which caused intense pain of the wrist during some months. During the operation an enlongated muscle directly below the extensor tendon, was found which was covered by the extensor retinaculum. It is an extensor digiti brevis manus, which exists in amphibia and is replaced in man by the long tendonous part of the extensor digitorum.