Absence of the Palmaris Longus In Vivo in Local Populations of Michigan Residents

Karwacki, David, Kevin Kalnasy, and Mary Tracy-Bee

Palmaris Longus is a muscle found on the anterior surface of the forearm.  When stimulated, it serves as a weak flexor of the wrist.  This muscle has received great attention as it is found to be missing in a variable percentage of the population.  We evaluated the absence and presence of this muscle’s tendon in 207 individuals from this vicinity.  Of those individuals, we determined if the muscle was unilaterally or bilaterally present or absent.  The muscle was found to be missing in approximately 20% of the population.  This was not significantly different for African-American, Caucasian or Hispanic individuals (X2=4.792, p=0.091),  contrary to other studies.  Furthermore, a significant difference was not identified due to sex, as males and females exhibited similar rates of absence (X2=0.242, p=0.374).  This provides insight into the abundance of this muscle and has implications on its clinical use in tendon grafting.