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 three-headed structure with variable morphology. Materials and methods: During a routine dissection of the posterior abdominal wall of a 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 three-headed psoas major muscle composed of superficial, intermediate and deep heads was identified. Conclusions: It is important to be aware of morphological variability of muscles, especially those considered to be constant, since an anomalous structure might interfere not only with their functions, but also lead to further clinical consequences.