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Surg Radiol Anat. 2019 Jul;41(7):845-848. doi: 10.1007/s00276-018-02176-6. Epub 2019 Feb 13.

Case report: absence of the right piriformis muscle in a woman.

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Division of Clinical and Functional Anatomy (Director: o.Univ.Prof. Dr. H. Fritsch), Medical University of Innsbruck, Muellerstrasse 59, 6020, Innsbruck, Austria.
Chirurgia Plastica Ricostruttiva ed Estetica, Policlinico 'Paolo Giaccone' di Palermo, Palermo, Italy.
Department of Surgical Oncological and Oral Science (DiChiRonS), Palermo University, Palermo, Italy.


We report a very rare case of a unilaterally absent piriformis muscle in a 60 year old woman. Accompanying variations comprised a common gluteal artery (instead of two distinct superior and inferior gluteal arteries), and an absent gemellus inferior muscle. The contralateral left side showed a normally developed piriformis muscle. In hominoids, the piriformis is constant, but is regularly missing in several other vertebrates. The piriformis muscle is an anatomical landmark for ultrasound investigations and ultrasound-guided interventions in the deep gluteal region such as a superior gluteal nerve block or even a sacral plexus block, also for any surgical approach such as total hip arthroplasty. A missing piriformis muscle therefore affects the orientation in the deep gluteal region and therefore the identification of the targeted structures.


Anatomical variation; Common gluteal artery; Deep gluteal region; Gemellus inferior muscle; Piriformis muscle


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