A three-headed piriformis muscle: an anatomical case study and narrative review of literature

The piriformis muscle (PM) is found in the gluteal region, exiting the pelvisthrough the greater sciatic foramen and dividing it into the suprapiriform andinfrapiriform foramina. The piriformis works as part of the hip external rotatormuscle group, and is responsible for rotation of the femur upon h...

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Bibliographic Details
Published in:Folia morphologica 2023-01, Vol.82 (4), p.969-974
Main Authors: Kozioł, T., Chaba, W., Janda, P., Ochwat, K., Pękala, P., Balawender, K., Walocha, J. A., Zarzecki, M. P.
Format: Article
Language:English
Subjects:
Anesthesia
Cadavers
Computed tomography
Ethics
Femur
Hip
Hip joint
Local anesthesia
Medical schools
Pelvis
Prenatal development
Sacrum
Sciatic nerve
Tomography
Trochanter
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Summary:The piriformis muscle (PM) is found in the gluteal region, exiting the pelvisthrough the greater sciatic foramen and dividing it into the suprapiriform andinfrapiriform foramina. The piriformis works as part of the hip external rotatormuscle group, and is responsible for rotation of the femur upon hip extensionand abduction of the femur during flexion of the hip joint. The aim of the presentreport is to describe a very rare case of the primary three-headed PM. To thebest knowledge of the authors, the said variant has not yet been described inthe existing literature.The 71-year-old male formalin-fixed cadaver was subjected to routine dissection.After careful removal of the connecting tissue, three separate, primary heads ofthe PM were identified. The lower head of the PM arose from the middle partof the sacral bone; 87.56 mm long and 9.73 mm wide. The medial head wasattached to the internal part of the posterior inferior iliac spine; 121.6 mm longand 20.97 mm wide. The upper head was attached to the external part of theposterior inferior iliac spine; 78.89 mm long and 23.94 mm wide. All headsconverged into a common tendon which inserted onto the greater trochanter.The clinical importance of this work comes down to the fact that the aberrant PMmay be the reason behind the piriformis syndrome and its associated symptoms.Moreover, knowledge regarding the variant anatomy of the PM is of immenseimportance to, e.g. anaesthesiologists performing computed tomography- orultrasound-guided sciatic nerve injection for local anaesthesia, radiologists interpretingimaging studies, and surgeons, especially during posterior approaches tothe hip and pelvis.
ISSN:0015-5659
1644-3284
DOI:10.5603/FM.a2022.0108