Prevalence of the palmaris longus in relation to the hand dominance

The incidence of left-handedness in the general population is between 8 and 15%. There is a presumption that the prevalence of palmaris longus muscle differ between right-handed and left-handed people. This prospective study was conducted to determine the prevalence of the palmaris longus in relation to the hand dominance. The study included 542 subjects (216 male and 326 female). They were initially tested to hand dominance and after that they were asked to do the standard test (Schaeffer's test) for the assessment of the palmaris longus tendon. If the tendon was not visualized or palpable, four additional tests (Thompson's test, Mishra's tests I and II, Pushpakumar's two-finger sign method) were done to confirm its absence. Right hand dominance was recorded in 452 (83.4%) subjects while the left hand dominance was recorded in 90 (16.6%) subjects. In right-handed subjects, palmaris longus tendon was absent on the right side in 24 (5.3%) and on the left side in 50 (11.1%) cases. In left-handed subjects, it was absent on the right side in 18 (20%) and on the left side in 2 (2.2%) cases. These differences were statistically significant. Bilateral absence of palmaris longus tendon was similar in both examined groups (25.1% in the overall series, 24.3% in right-handed subjects, 28.9% in left-handed subjects). The results of our study show that a right-sided absence was more common in left-handed persons while the left-sided absence was more common in right-handed persons. Unilateral tendon absence was more common on the non-dominant hand.