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

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

doi:10.4322/acr.2020.239

Josemberg da Silva Baptista, João Gabriel Alexander + Show 2 more

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https://doi.org/10.4322/acr.2020.239

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Abstract

ABSTRACTThe 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.

Highlights

The gluteal region contains important neurovascular and muscular structures that may impose diverse clinical and surgical approaches
After his section and bending, we noticed the absence of a distinct piriformis muscle (PM)
The extension part of the Gmed could be compared to what occurs in Babirusas, which can observe a complete fusion between Gmed and PM,[9] the origin of PM in the anterior surface of the sacrum is a well-established feature in hominoids,[10] which lead us to define that it is a PM absence case

Summary

Introduction

The gluteal region contains important neurovascular and muscular structures that may impose diverse clinical and surgical approaches. The prevalence of PM and SN variation is 16.9% in cadavers and 16.2% in surgical cases.[1] The main reported findings are related to muscle fusions and the topography of the SN, which lead to clinical and surgical debate, especially on the piriformis syndrome (PS).[2,3,4]. Over the years, these variations have been classified and distributed into different groups. Windisch et al.[3] developed two ways to classify the PM presentation: three types depending on its morphology, and in four types depending on its fusion and different insertion areas

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