An anomalous extensor indicis muscle.

A naval cook. aged twenty. complained of diffuse pain in the left hand after heavy use. with a swelling on the back of the hand. He had first noticed this swelling three years before. and said that it had appeared spontaneously. A course of short-wave diathermy had failed to relieve his symptoms. Examination showed an elongated tumour on the dorsum of the hand, which appeared to arise from the extensor tendons to the index finger and passed upwards under the extensor retinaculum of the wrist (Fig. I). It was soft, semi-fiuctuant and slightly tender. It was noted that it was not translucent, but the significance of this observation was not realised at the time. The appearance of the right hand was normal, but on palpation a slight thickening was felt in the line of the extensor tendons to the index finger. On questioning he admitted to occasional pain on the back of this hand also. The tumour was diagnosed as a ganglion and was explored. At operation it was found to be a muscle replacing the extensor indicis tendon. This muscle arose from the soft tissues on the dorsum of the wrist under cover of the extensor retinaculum. At the neck of the second