Sinestre, deviance, or biology? An investigation of hand dominance in relation to tendon absence

The present study aimed to examine the relationship between hand dominance and the presence or absence of the flexor digitorum superficialis (FDS) in the fifth digit to add to the current body of knowledge. We hypothesized that the absence of the FDS in the right small finger is more prevalent in left-handed individuals. This was a prospective study conducted from January 2020 to April 2021 and performed at the plastic surgery department of a university hospital. The sample consisted of volunteers with no history of upper limb trauma, surgery, or any other condition. The study included male and female individuals over 18 years old at a local Rhode Island university campus. The FDS tendons of the bilateral fifth fingers were evaluated through clinical testing by an independent examiner. A total of 236 hands from 118 volunteers were analyzed. Left-hand dominant participants composed of 5% of the population. For these participants, the prevalence of absence of the fifth finger FDS tendon in the right hand was significantly higher than that of right-hand dominant participants (71.4% vs. 28.8%). No significant difference between sex assigned at birth (male vs. female) was noted and the absence of the FDS in either hand, regardless of hand dominance. The results from the current study demonstrate that anatomy may contribute to one's preference for left-handedness. For children who have difficulty using their right hand, perhaps, an assessment of their FDS status may result in earlier acceptance of using their left hand.