6 - Correlating Intra-donor Presence of Vestigial Muscular Structures: Palmaris Longus, Psoas Minor, Plantaris, and Fibularis Tertius

Poster Board Number: 6
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Abstract Body : The human body contains a number of vestigial structures, including muscles that were once fully functional but have since become rudimentary or absent over evolutionary time. Some common vestigial muscles are palmaris longus (PL), psoas minor (PM), plantaris (PT), and fibularis tertius (FT). While the prevalence of these structures has been studied at the population level, the literature examining potential correlations between the relative presence/absence of these structures within an individual is limited. The current study investigates the intra-donor presence of PL, PM, PT, and FT.

Data were collected from willed-body donors from the Sam Houston State University College of Osteopathic Medicine's Human Anatomy Lab. The presence of PL, PM, PT, and FT, as well as the individual’s sex, were recorded for each donor (n = 19). Spearman’s rank was used to test for significant correlations in the relative presence/absence of multiple vestigial muscles in a single individual.

Significant correlations were found between the presence of the PL and PM muscles (r = -0.535; p = 0.018) and the PM and FT muscles (r = -0.497; p = 0.030). Negative correlation values indicate that the presence of PL was significantly associated with the absence of PM in a single individual, and the presence of PM was significantly associated with the absence of FT. No other pair of muscles showed a significant correlation, and donor sex was not significantly correlated with the presence/absence of any of the examined muscles.

The results of our study indicate that there is a significant negative intra-donor correlation between PL and PM, as well as PM and FT. A previous study found a significant intra-donor correlation between PL and FT; however, this was not replicated in our findings. Increased sample size in future studies may help to resolve this discrepancy. The significant negative correlations shown in our study may have clinical and surgical implications. For example, PL and PM are associated with the etiology of carpal tunnel syndrome and psoas minor syndrome, respectively, while PL and FT are useful surgically in grafting procedures and as orienting landmarks. These implications warrant further study into the correlations between the examined vestigial muscles. Future works will focus on examining intra-donor prevalence of PL, PM, PT, and FT with increased sample sizes.