Abstract
Purpose: Anatomical agenesis within a population is not well understood, with variations including but not limited to complete absence, unilateral presence, or bilateral presence. Agenesis of human vestigial muscles including the palmaris longus (PL), fibularis tertius (FT), and psoas minor (PM) has been studied; however, the relationship between their presence and absence has not been examined. The purpose of this study is to analyze the prevalence of the PL, FT, and PM muscles, investigate any relationship of prevalence based on sex or race, and investigate any correlation between the presence or absence of each muscle within individual donors.Methods: Twenty-three willed body donors were comprehensively dissected by medical students, and the presence or absence of the PL, FT, and PM muscles was recorded.Results: The PL was present bilaterally in 87% of donors and absent bilaterally in 13%. The FT was present bilaterally in 96% of donors, and present unilaterally in 4% of donors. There was no evidence of total agenesis of the FT within our sample. The PM was present bilaterally in 39% of donors, and absent bilaterally in 61% of donors. No statistically significant relationship was indicated between muscle presence and the sex or race of the donors. No correlation between the presence or absence of each of the muscles was found.Conclusion: In this sample of willed body donors, there was no relationship between muscular agenesis of the vestigial muscles. This suggests that muscle agenesis is a local genetic developmental event at each muscle, and that there is not a single developmental event that leads to agenesis of multiple vestigial muscles. Further understanding of the agenesis of vestigial structures within populations and subpopulations can aid in physician diagnosis and understanding of the anatomical makeup of individuals.
Highlights
Anatomical muscular agenesis within a population is not well understood, with variations including complete absence, unilateral presence, or bilateral presence of the muscles
Despite common literature stating an absence of 15%, the palmaris longus (PL) muscle has the greatest variability in prevalence of any muscle in the human body, with absence ranging from 2% to 64%, with a direct correlation with ethnicity [4]
The present study failed to find any significant correlations for psoas minor (PM) muscle presence or absence, this study suggests an area of further investigation that may help with clinical and surgical improvements
Summary
Anatomical muscular agenesis within a population is not well understood, with variations including complete absence, unilateral presence, or bilateral presence of the muscles. Agenesis is common in human vestigial structures, which are structures with varying degrees of prevalence and functionality within a population due to the course of evolution [1]. The extent of functional vestigiality of the PL muscle is highlighted by (1) a lack of diminished function of the wrist and forearm after intraoperative injury to the PL muscle and (2) congenital absence showing no functional loss of grip or finger flexion strength [2,3]. Through a meta-analysis, there appear to be inconclusive results in regards to unilateral
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