Autopsy and Case Reports
Autopsy and Case Reports
Autopsy Case Report

The absence of piriformis muscle, combined muscular fusion, and neurovascular variation in the gluteal region

Matheus Coelho Leal; João Gabriel Alexander; Eduardo Henrique Beber; Josemberg da Silva Baptista

Downloads: 0
Views: 1031


ABSTRACT: The gluteal region contains important neurovascular and muscular structures with diverse clinical and surgical implications. This paper aims to describe and discuss the clinical importance of a unique variation involving not only the piriformis, gluteus medius, gluteus minimus, obturator internus, and superior gemellus muscles, but also the superior gluteal neurovascular bundle, and sciatic nerve. A routine dissection of a right hemipelvis and its gluteal region of a male cadaver fixed in 10% formalin was performed. During dissection, it was observed a rare presentation of the absence of the piriformis muscle, associated with a tendon fusion between gluteus and obturator internus, and a fusion between gluteus minimus and superior gemellus muscles, along with an unusual topography with the sciatic nerve, which passed through these group of fused muscles. This rare variation stands out with clinical manifestations that are not fully established. Knowing this anatomy is essential to avoid surgical iatrogeny.


Anatomic Variation, Anatomy, Buttocks, Muscle, Piriformis Muscle Syndrome


1 Smoll NR. Variations of the piriformis and sciatic nerve with clinical consequence: a review. Clin Anat. 2010;23(1):8-17. PMid:19998490.

2 Beaton LE, Anson BJ. The relation of the sciatic nerve and of its subdivisions to the piriformis muscle. Anat Rec. 1937;70(1):1-5.

3 Windisch G, Braun EM, Anderhuber F. Piriformis muscle: clinical anatomy and consideration of the piriformis syndrome. Surg Radiol Anat. 2007;29(1):37-45. PMid:17216293.

4 Brenner E, Tripoli M, Scavo E, Cordova A. Case report: absence of the right piriformis muscle in a woman. Surg Radiol Anat. 2019;41(7):845-8. PMid:30758526.

5 Frazer JE. The insertion of the pyriformis and obturator internus, and formation of the posterior circular capsular fibres and upper retinaculum of weitbrecht. J Anat Physiol. 1904;38(Pt 2):170-85. PMid:17232598.

6 Knott J. Muscular anomalies, including those of the diaphragm, and subdiaphragmatic if the human body. Proc R Ir Acad. 1883;3:627-41.

7 Macalister A. Additional observations on the muscular anomalies in human anatomy. (Third Series) with a Catalogue of the Principal Muscular Variations Hitherto Publisher. Trans Roy Irish Acad Sci. 1875;25:1-134.

8 Chang C, Jeno SH, Varacallo M. Anatomy, bony pelvis and lower limb, piriformis muscle. In: StatPearls. StatPearls [Internet] [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 [cited 2020 Jul 1]. Available from:

9 Macdonald AA, Kneepkens AFLM. Descriptive and comparative myology of the hindlimb of the babirusa (Babyrousa babyrussa L. 1758). Anat Histol Embryol. 1995;24(3):197-207. PMid:8546328.

10 Ferrero EM, Pastor JF, Fernandez F P, Cachorro MB, Diogo R, Wood B. Comparative anatomy of the lower limb muscles of hominoids: attachments, relative weights, innervation and functional morphology. In: Hughes EF, Hill ME. Primates: classification, evolution and behaviour. Hauppauges: Nova Science Publishers; 2012. p. 1-70.

11 Duda GN, Brand D, Freitag S, Lierse W, Schneider E. Variability of femoral muscle attachments. J Biomech. 1996;29(9):1185-90. PMid:8872275.

12 Nicholson H, Woodley S, Flack N. Gluteal muscles and lateral rotators of the hip. In: Tubbs RS, Shoja MM, Loukas M, editors. Bergman’s comprehensive encyclopedia of human anatomic variation. Hoboken: John Wiley & Sons, Ltd; 2016. p. 386-409.

13 Caetano AP, Seeger LL. A rare anatomical variant of unilateral piriformis muscle agenesis: a case report. Cureus [Internet]. 2019; [cited 2020 Oct 20];11(6):e4887. Available from:

14 Varenika V, Lutz AM, Beaulieu CF, Bucknor MD. Detection and prevalence of variant sciatic nerve anatomy in relation to the piriformis muscle on MRI. Skeletal Radiol. 2017;46(6):751-7. PMid:28280851.

15 Pokorný D, Jahoda D, Veigl D, Pinskerová V, Sosna A. Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty. Surg Radiol Anat. 2006;28(1):88-91. PMid:16311716.

16 Natsis K, Totlis T, Konstantinidis GA, Paraskevas G, Piagkou M, Koebke J. Anatomical variations between the sciatic nerve and the piriformis muscle: a contribution to surgical anatomy in piriformis syndrome. Surg Radiol Anat. 2014;36(3):273-80. PMid:23900507.

Submitted date:

Accepted date:

Publication date:

602d71b60e8825f81642f8ca autopsy Articles
Links & Downloads

Autops Case Rep

Share this page
Page Sections