Prevalence of the palmaris longus through clinical evaluation

Most standard textbooks of hand surgery report on the rate of palmaris longus muscle absence of 15%. The aim of the study was to determine the absence of palmaris longus and to correlate it with age, sex and body side.

The study included 800 subjects (400 male and 400 female). They were initially asked to do the standard test for the assessment of the palmaris longus tendon. If the tendon was not visualized or palpable, four additional tests were done to confirm its absence.

Unilateral absence of the palmaris longus was recorded in 173 (21.6%) and bilateral in 127 (15.9%) study subjects. According to body side, right-sided absence of palmaris longus was found in 69 (8.6%) and left-sided in 104 (13%) subjects, yielding a statistically significant difference. Bilateral absence was slightly more common in men. The prevalence of palmaris longus absence on the right and left side was similar in men, whereas in women it was significantly more common on the left side. Differences between the three age groups (young, middle-aged and old) were not significant; however, the middle-aged and young groups showed a lower rate of palmaris longus presence as compared to old-age group.

It has been suggested that this tendon is rapidly disappearing in humans. The results of our study show a relatively high incidence of tendon absence and pointed to more pronounced loss of the muscle on the left side.