Distribution patterns of the muscular branch of the median nerve in the thenar region.

Studies on the distribution patterns of the muscular branch of the median nerve to the thenar muscles are scarce. Available accounts give only general descriptions. To establish the distribution pattern more precisely, we dissected 60 palmar regions from 30 cadavers of adult individuals, ranging in age from 23 to 77 y. The distribution pattern of the muscular branch was classified into 3 types. In 50% of subjects there were branches to the superficial head of flexor pollicis brevis (FPB), abductor pollicis brevis (APB) and opponens pollicis (OP) (type I). In 40% there were branches only to APB and OP (type II). In the remainder (type III) the muscular branch provided independent branches to APB, OP and FPB, to APB and OP, or to APB and FPB, after dividing precociously. Types I and II were further subdivided according to the site, direction and number of the individual branches.