A study on the extensor digiti minimi muscle in man
Yoshida, Y.
Kaibogaku Zasshi. Journal of Anatomy 60(3): 185-196
1985
ISSN/ISBN: 0022-7722 PMID: 3832753 Document Number: 250229
An anatomical study was made about the extensor digiti minimi in man, using 322 upper extremities from 161 (102 male, 59 female) cadavers. The morphological and phylogenetic significance of the extensor digiti minimi was discussed. The extensor digiti minimi was subject to great variability among the upper extremities, so that it was classified into 8 types: type 1; The muscle formed a belly and ended in a single tendon which was attached to the little finger. type 2; The muscle had a belly and a single tendon. The tendon split into 2 near the carpus, and both parts were inserted into the little finger. The type 2 comprised 3 subtypes. type 3; The muscle formed a belly and ended in 2 tendons which were attached to the little finger. The type 3 comprised 4 subtypes. type 4; The muscle had a belly and 3 tendons. All the 3 tendons were inserted into the little finger. The type 4 comprised 2 subtypes. type 5; The muscle formed a belly and terminated in 1, 2 or 3 tendons. The most radial tendon bifurcated in hand to supply the ring finger and little finger, and the other went to the little finger. The type 5 comprised 4 subtypes. type 6; The muscle had a belly and 2 tendons. The radial tendon was attached to the 5th metacarpal bone, while the ulnar was inserted into the little finger. type 7; There were 2 distinct bellies and 2 tendons. The tendon of the radial belly was inserted into the little finger, and that of the ulnar belly into the ulnar carpal bones. type 8; The extensor digiti minimi muscle was completely absent. The type 1 was present in 51, type 2 in 151, type 3 in 80, type 4 in 2, type 5 in 33, type 6 in 1, type 7 in 2, and type 8 in 2 out of 322 upper extremities. The extensor digiti minimi had 1 or 2 tendons arising from a single belly and inserted into the little finger in 87.6% (types 1, 2 and 3). And the muscle which had tendons arising from a single belly and attached to the little finger and ring finger was observed in 10.3% (type 5), but the tendon for the ring finger was small. The extensor digiti minimi was derived from the extensor digitorum quinti et quarti proprius of mammals. And the radial segment of it was undergoing further reduction in primates. In most instances the extensor digiti minimi was only inserted into the little finger in man.