A three-headed psoas major muscle: a case report

Abstract

Background: Multiple anatomical variations, from anomalous courses to additional structures, have been reported in muscles from different compartments of the human body. We report an extremely rare case of a psoas major muscle presenting as a 3-headed structure with variable morphology. Materials and methods: During a routine dissection of the posterior abdominal wall of an 82-year-old male cadaver, an anomalous PM muscle with supernumerary head was identified, photographed, and subjected to further measurement. Results: Although the anatomy of the dissected posterior abdominal wall structures was typical, a 3-headed psoas major muscle composed of superficial, intermediate, and deep heads was identified. Conclusions: It is important to be aware of the morphological variability of muscles, especially those considered to be constant, because an anomalous structure might not only interfere with their functions but also lead to further clinical consequences.