Thumb opponency movement: anatomical considerations

Abstract

A variety of clinical cases observed in isolated lesions of the median and ulnar nerves does not agree with the classic pattern of innervation of the muscles from the thenar region. MATERIAL AND METHODS: We have studied the dissections of 40 hands of 20 fresh adult cadavers. The sex distribution was 18 males and 2 females. We investigated the innervation of the thenar muscles. RESULTS: The “abductor pollicis brevis” and the “oponens pollicis” muscles are innerved exclusively by the median nerve. The superficial head of “flexor pollicis brevis” has been innervated by the median nerve in 29 of the hands. In 11 received double innervation (from median and ulnar nerves).The deep head of “flexor pollicis brevis” showed a different find: in 27 there is double innervation, in 12 % the ulnar nerve is the exclusive nerve. DISCUSSION AND CONCLUSION: According with our studies the pattern of the innervation more frequent in relation to the “flexor pollicis brevis” muscles, and that must be considered as normal pattern, is that the superficial head receives innervation of the median nerve and the deep head receives innervation of the ulnar and median nerves. The “abductor pollicis brevis” and the “oponens pollicis” muscles are innerved exclusively by the median nerve The oblique head of “adutor pollicis” was innerved only by the ulnar nerve in 30 pieces, and in 10 the innervation was double. The transverse head of “adductor pollicis” received the ulnar nerve innervation in all dissected hands.