A Morphological Study on the Human Palmaris Longus Muscle

Examing the form of palmaris longus muscle (MPL) of 82 cadavers (male : 52 bodies, female : 30 bodies) with 164 side cases of Japanese adults, we took the statistics of frequency of variational muscles' appearance. Furthermore, about the lacks of muscles, we examined the existence of MPL by observing 201 students (160 males and 41 females) with 402 side cases in order to compare those of autoptical bodies with those of living bodies. We reached the following conclusions. 1) There were 2 bodies (2.4%) with 2 side cases (1.2%) of which belly existed at central. Besides, concerning both cases muscle were innervated by median nerve and concerning suppliting artery, only the branch from ulnar artery distributed. 2) The lacks of MPL were observed in 6 bodies (7.3%) with 7 side cases (4.3%). 3) The lacks of MPL of the living bodies were observed in 16 bodies (8.0%) with 20 side cases (5.0%) i.e. a slightly higher frequencies than autoptical bodies. The ratio of the lacks of MPL on right side was higher than those on left side in both living bodies and autoptical bodies. 4) The origins of palmar aponeurosis (AP) could be classified as follows. Type I had a normal MPL of which tendon transfered to AP…150 side cases (91.5%). Type IIA : Palmaris longus tendon (TPL) branched off into two bundles. One bundle merged with flexor retinaculum (RF) and the other transfered to AP…6 side cases (3.7%). Type II-B-fds : This type lacked MPL and AP originated from flexor digitorum superficialis (in 4 side cases, 2.4%). Type IIB-fcr : MPL lacked and AP originated from flexor carpi radialis (in 1 case. 0.6%). Type IIB-fcu : MPL lacked and AP originated from flexor carpi ulnaris (none). Type IIIA : Tendon of MPL ended at flexor retinaculum and AP originated from RF (in 1 case, 0.6%). Type IIIB : MPL lacked from Type IIIA (in 2 cases, 1.2%). 5) The average length of MPL in normal case were studied in 81 bodies (51 male bodies, 30 female bodies) and in 155 side cases (99 male side cases, 56 female side cases). Results were as follows. Total average length was 234.3mm. The average length of muscle was 116.3mm. The average length of tendon was 118.1mm. Average ratio of total length of muscle to that of total length of tendon was 49.6 : 50.4.