title: The psoas quartus muscle.
abstract: We report an unusual finding in an adult male cadaver. During the routine dissection of the posterior abdominal wall as part of an anatomy course at our institution, an anomalous muscle was noted. This muscle originated from the transverse process of the left L3 vertebrae and the medial aspect of the quadratus lumborum. We believe this muscle to represent a variety of the psoas quartus that, to our knowledge, has only been described once before in the extant medical literature. The presence of a psoas quartus muscle may contribute to femoral nerve compression. The clinician may wish to consider this rare muscular anomaly in patients with symptoms of femoral nerve compression in which no other clear etiology is found. Furthermore, clinicians who image the posterior abdominal wall should be aware of this potential anomaly when interpreting the anatomy of this region.
authors.affiliation: Department of Cell Biology, University of Alabama at Birmingham, Alabama, USA. rstubbs@uab.edu
authors.forename: R Shane
authors.initials: RS
authors.lastname: Tubbs
authors.forename: W Jerry
authors.initials: WJ
authors.lastname: Oakes
authors.forename: E George
authors.initials: EG
authors.lastname: Salter
mesh_terms: D000368:Aged; D005267:Femoral Nerve / Q000033:anatomy & histology* / Q000473:pathology; D014644:Genetic Variation; D006801:Humans; D008160:Lumbosacral Plexus / Q000033:anatomy & histology*; D008297:Male; D009408:Nerve Compression Syndromes / Q000175:diagnosis; D016658:Psoas Muscles / Q000002:abnormalities*