Reappraisal of the anatomical diversity of the pyramidalis muscle with its substantial clinical applicability: Cadaveric analysis

Abstract

Abstract Purpose: The study aimed to analyze the anatomical diversity of the pyramidalis muscle (PM), their association with sex, laterality and possible role in muscle biomechanics. Materials & Methods: 51 formalin-fixed cadavers (36 males and 15 females) were examined for PM. Based on the mode of insertion or the level of apex, the formation of the muscle was classified into nine patterns. Observations: PM was more prevalent bilaterally (39.21%) than unilaterally (1.96%) (p=0.001) and more frequently in males (41.67%) than in females (40%). (p>0.05). Side symmetry was detected except in one case and Type 7 was the most common form. The mean length of PM in males and females was 4.51±0.14 and 3.33±0.12 cm on the right and 4.51±0.11 and 3.26±0.16 cm on the left side. The mean width of right-sided PMs in males and females was 1.90±0.17 and 1.58±0.13 cm and left-sided 1.88±0.14 and 1.55±0.38 cm. mean of Pyramidalis-puboumbilical index (PPI) in males and females was 32.82±1.65 and 27.50±1.08 respectively. The mean insertion angle was 24.56±3.07 on right and 23±2.03 on the left side (p=0.03). Male predominance existed on right and left-sided PM length (p<0.001 and p<0.001), width (p=0.001) and PPI (P=0.001). The strong positive correlation (r=0.83) between length and width indicates a symmetrical muscle augmentation in the two dimensions. Conclusion: PM is an inconsistent anatomical structure with persistent morphology. The level and angle of insertion into the linea are crucial in the biomechanics of linea alba. PPI, determining the level of termination would be useful to surgeons making midline infra-umbilical incisions.