Supernumerary flexor carpi ulnaris--case report and review.

Anomalies of Flexor carpi ulnaris (FCU) are uncommon and predominantly consist of abnormal insertion or extra tendinous bands. The presence of two separate bellies of FCU muscle with separate tendons has been termed as Digastric FCU. It is a very rare anomaly with only six previously reported cases and no report of clinical use of such anomalous muscle. We describe a case of anomalous FCU found incidentally in a patient operated for complex Post Volkmann's ischemic contracture deficits. On table each head of FCU was found to form separate belly and tendon. One tendon was used for the thumb opposition while the other for index finger flexion. Postoperatively, the patient had independent movement of thumb and index finger. This is the first reported case of clinical application of digastric FCU. We reviewed the literature for supernumerary FCU in general and digastric FCU in particular. We propose a new classification for supernumerary FCUs based on the clinical appearance and the probable embryological basis of the anomaly: Type 1 (Split tendons)--single muscle with two tendons; Type 2 (Digastric FCU)--for each head of FCU forming separate muscle bellies and tendons; and Type 3 (Accessory FCU)--abnormal muscle adjacent to normal FCU with combined features of FCU and Palmaris longus.