Introduction The psoas muscle group is part of the posterior abdominal wall and is comprised of long muscles - major, minor, and tertius. Out of those, only the psoas major muscle is an obligatory muscle present in all individuals. The psoas minor muscle (PMM) originates as vertical fascicles inserted in the bodies of the last thoracic and first lumbar vertebrae and inserting into the iliopectineal eminence. The muscle provide flexion of the lumbar spine in a limited fashion. The aim of the study was to establish the frequency of the muscle in the Bulgarian population. Materials and methods This study was carried out in the Department of Anatomy and Cell Biology, Medical University, Varna, Bulgaria, by Dr. Paraskev Stoyanov in November 2017, on a total of 10 cadavers. The length, width, and circumference of the muscles were measured. The collected data were interpreted in a descriptive manner. Results The PMM was present in six out of ten cadavers (60%). Out of those six cadavers, the muscle was bilateral in three, unilateral on the left side in one, and unilateral on the right side in two cadavers. The average length of the muscle was 19.66 cm (range:14.4 cm - 21.7 cm), average width was 1.73 cm (range: 1.0 cm - 3.2 cm ) and average circumference was 3.48 cm (range: 1.7 cm - maximum 5.6 cm). The male to female ratio of cadavers with a PMM was 1:1. Conclusion The frequency of the muscle's variations considering its presence in the Bulgarian population (60%) is higher when compared to its presence in the Indian population (36.67%), virtually identical to the Brazilian population (59%), and lower than that reported in the US (65.6%). The morphometric analyses of the different populations showed a shorter psoas minor in the Bulgarian population.
Keywords: bulgaria; morphometric study; psoas minor; psoas minor morphology; psoas muscle.