Anatomical Relationships in Vestigial Muscle Presentation: A Multi-institutional Anatomic Study

There are separate poster presentation times for odd and even posters.
Odd poster #s – first hour
Even poster #s – second hour

Co-authors:

Rylie Wackerly - College of Osteopathic Medicine, Sam Houston State University; Dennis Wooten - College of Osteopathic Medicine, Sam Houston State University; Elizabeth Maynes - Uniformed Services University of Health Sciences

The presentations of vestigial muscles palmaris longus (PLL), plantaris (PLN), and fibularis tertius (FBT) are highly variable between populations, as demonstrated in the literature. Understanding the variations in these and other vestigial muscles may be important clinically, surgically, and paleoanthropologically. Few studies exist exploring whether various presentations of PLL, PLN, and FBT are associated with laterality or relative intra-individual vestigial muscle presence. This study aims to investigate whether various presentations of PLL, PLN, and FBT within individuals occur independent of laterality, sex, and relative intra-individual vestigial muscle presence.
Data were collected from cadavers from human anatomy labs of Sam Houston State University College of Osteopathic Medicine (SHSUCOM) and the Uniformed Services University of Health Sciences (USUHS). Associations between intra-individual vestigial muscle presence, laterally, presentation, and/or sex were evaluated using chi-square. Patterns of PLL, PLN, and FBT presentation in each individual was evaluated via descriptive statistics and frequency tables.
The resulting chi-square statistics evaluating associations of laterality and sex between PLL presence and FBT presence showed a significant association with 56.14% of male cadavers having right PLL and right FBT (x2 = 6.521, df = 1, p = .011). No other associations of laterality and sex between presence of the examined vestigial muscles were observed. The resulting chi-square statistics testing associations between intra-individual vestigial muscle presentation of PLL and PLN and/or sex showed significant association between bilateral presence of PLL and PLN (x2 = 20.093, df = 9, p = .017) with a frequency of 61.4% in all cadavers, excluding sex. Significant association was observed between bilateral PLL and FBT in male cadaver (x2 = 21.304, df = 9, p = .011) with a frequency of 53.13%; and in all cadavers (x2 = 23.353, df = 9, p = .005), excluding sex, with a frequency of 47.37%.
These results show a significant association between presence of right PLL and right FBT in males, bilateral presence of PLL and FBT in males and for all individuals regardless of sex, and bilateral presence of PLL and PLN in all individuals. Whether any of these findings display any clinical or surgical utility remains unclear. Further study is required, particularly inferential statistical analysis of larger samples, to determine whether the observed associations illustrated in this study may be applied at the population level. These nuances can aid in our understanding of human anatomy and evolution, providing valuable insights for researchers and clinicians.