Introduction:
The posterior abdominal wall is a complex region of human anatomy. It is formed by the lumbar vertebrae, pelvic girdle and the five main posterior abdominal muscles - the iliacus, psoas major, quadratus lumborum, the diaphragm, their associated fascia and the variable psoas minor and tertius muscles. The psoas muscle group is comprised of the long fusiform muscles - major, minor and tertius, with only the psoas major muscle being an obligatory muscle present in all individuals. The psoas muscle group however are extremely variable and have differences not only in their structure and morphology, but also in their innervation. The psoas minor is an extremely variable inconstant muscle, a prime example for a vestigial structure in the human body.
Case report:
During a standard posterior abdominal wall dissection of an adult female cadaver a unilateral right-sided psoas minor muscle was established, with a complete absence of the same muscle on the contralateral left side. The unilateral right-sided psoas minor muscle was located superficially and laterally to the psoas major muscle, it was fusiform in shape and its body measured 96 mm in length and 16mm in circumference.
Conclusion:
The psoas muscle group is one of the most variable muscle groups in the human body. It could be bilaterally - located on both sides of the vertebral column on the anterior surface of psoas major muscle. Our case is representative of one of the not so common variations of the psoas minor muscle with muscle morphology extremely representative of this type of unilateral variation.
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