Prevalence and pubo-umbilical index of pyramidalis muscle in a select Kenyan population.

Purpose: Pyramidalis is a lower anterior abdominal wall muscle that is considered vestigial and shows variations in prevalence and size. It's been utilized as an anatomical landmark and harvested for use in various surgical procedures. Despite knowledge of its clinical importance, data on the prevalence of pyramidalis remain absent from the Kenyan population with few studies globally reporting on its pubo-umbilical index. We therefore aimed to determine the prevalence and relative lengths (pubo-umbilical index) of pyramidalis muscle in a sample Kenyan population.

Materials And Methods: Fifty-two cadavers (41 males, 11 females) from the Department of Human Anatomy, University of Nairobi were used. Prevalence and length of the muscle (l) were established, and the distance between pubic symphysis and umbilicus (L) measured and used to calculate pubo-umbilical index (l/L ×100%). Independent and paired T tests were done, using SPSS® version 22. A p value of ≤ 0.05 was considered statistically significant at a 95% confidence interval.

Results: Pyramidalis was present in 84% (44) of cadavers; 83% (43) bilaterally, 2% (1) unilaterally, and 85.4% (35) in males, 81.8% (9) in females. Mean length in males and females was 71.8 ± 35 mm and 63.5 ± 37.5 mm, respectively. Mean pubo-umbilical index was 38% ± 18 (39 % ± 18 males, 35% ± 19 females). No statistically significant difference was found.

Conclusion: Pyramidalis is a highly prevalent muscle in the Kenyan population and, hence, could be exploited for its clinical and surgical utilities. The muscle terminates largely within the 2nd quarter (25-50%) of the infra-umbilical linea alba measured from pubic symphysis. Its pubo-umbilical index would be useful to surgeons making midline infra-umbilical incisions and performing procedures involving the muscle.