The Variation in the Absence of the Palmaris Longus in a Multiethnic Population of the United States: An Epidemiological Study

The absence of the palmaris longus (PL) has been shown to vary based on body side, gender, and ethnicity. In prior studies, homogenous ethnic populations have been shown to have differences in rates of absence. However, no study thus far has analyzed the differences in palmaris longus prevalence in a multiethnic population. We prospectively collected data on 516 patients visiting the outpatient hand clinics at LAC+USC Medical Center and Keck Medical Center. Analysis of the data was then performed for variables including ethnicity, laterality, and gender. There were no differences in the absence of the PL based on laterality or gender. Ethnically, there was no difference between white (non-Hispanic) and white (Hispanic) patients, with prevalence of 14.9% and 13.1%, respectively. However, African American (4.5%) and Asian (2.9%) patients had significantly fewer absences of the PL than the Caucasian, Hispanic reference group (P = 0.005 and P = 0.008, resp.). African Americans and Asians have a decreased prevalence of an absent PL. The Caucasian population has a relatively greater prevalence of an absence of the PL. This epidemiological study demonstrates the anatomic variation in this tendon and may be taken into account when planning an operation using tendon grafts.