Morphometry and Frequency of the Pyramidalis Muscle in Adult Humans: A Pyramidalis Muscle's Anatomical Analysis.

Objectives: To verify the pyramidalis muscle's frequency (bilaterality, unilaterality, or absence) and morphometry (length of the medial border and width of its origin/base) in a sample of the Brazilian population and the anthropometric influence.

Methods: Dissection of 30 cadavers, up to 24h post-mortem.

Results: The pyramidalis muscle was present bilaterally and unilaterally in 83.33% and 3.33% of the cadavers, respectively, and absent in 13.33%. The muscles on the right and left sides were symmetrical in length but not in width; the pyramidalis muscles of men were longer, while those of the women were wider. We also found that there was greater variation in the dimensions (length and width) of the men's muscles. Finally, in this sample of the Brazilian population, the pyramidalis muscle's unilaterality was more prevalent than in other populations, and its complete absence was less prevalent.

Conclusions: There were no cases of muscle duplication in one or both sides, as described in some studies. Despite all of its morphometric variation, the pyramidalis muscle maintained its triangular shape with longitudinal fibers in every case. Furthermore, no statistically significant correlation was noted between the muscles' dimensions and person's age, height, weight, or gender.