A Case of Reverse Palmaris Longus Muscle- An Additional Muscle in the Anterior Compartment of the Forearm

It is uncommon to have additional muscles in the upper limb. Some of them may restrict the movements or compress the nerves and vessels, while others may go unnoticed. During the routine dissection for undergraduate medical students, we observed an additional muscle in the anterior compartment of the forearm in about 60-year-old male cadaver. The muscle had a prominent belly and a long tendon. Distally, it was attached to the flexor retinaculum by a short and thick tendon. Proximally, long tendon of the muscle passed between the flexor carpi ulnaris and palmaris longus and was attached to the common aponeurosis shared by the extensor carpi ulnaris and flexor digitorum profundus muscles. The additional muscle belly was supplied by a branch from the anterior interosseous nerve. The ulnar nerve and artery was passing deep to the fleshy belly of the muscle. The muscle reported here might compress the ulnar nerve and artery and may produce neurovascular symptoms. On the other hand, the tendon and fleshy belly of the muscle could be useful in muscle/tendon grafts. The observations made by us in the present case will supplement our knowledge of variations of the muscles in this region which could be useful for surgeons during the forearm and hand surgeries.