Anthropometric Study of the Piriformis Muscle and Sciatic Nerve: A Morphological Analysis in a Polish Population

Robert Haładaj, Mariusz Pingot, Michał Polguj, Grzegorz Wysiadecki, Mirosław Topol, Robert Haładaj, Mariusz Pingot, Michał Polguj, Grzegorz Wysiadecki, Mirosław Topol

Abstract

BACKGROUND The aim of this study was to determine relationships between piriformis muscle (PM) and sciatic nerve (SN) with reference to sex and anatomical variations. MATERIAL AND METHODS Deep dissection of the gluteal region was performed on 30 randomized, formalin-fixed human lower limbs of adults of both sexes of the Polish population. Anthropometric measurements were taken and then statistically analyzed. RESULTS The conducted research revealed that, apart from the typical structure of the piriformis muscle, the most common variation was division of the piriformis muscle into two heads, with the common peroneal nerve running between them (20%). The group with anatomical variations of the sciatic nerve course displayed greater diversity of morphometric measurement results. There was a statistically significant correlation between the lower limb length and the distance from the sciatic nerve to the greater trochanter in the male specimens. On the other hand, in the female specimens, a statistically significant correlation was observed between the lower limb length and the distance from the sciatic nerve to the ischial tuberosity. The shortest distance from the sciatic nerve to the greater trochanter measured at the level of the inferior edge of the piriformis was 21 mm, while the shortest distance to the ischial tuberosity was 63 mm. Such correlations should be taken into account during invasive medical procedures performed in the gluteal region. CONCLUSIONS It is possible to distinguish several anatomical variations of the sciatic nerve course within the deep gluteal region. The statistically significant correlations between some anthropometric measurements were only present within particular groups of male and female limbs.

Figures

Figure 1
Figure 1
A typical morphology of the piriformis muscle and a typical course of the sciatic nerve in the infra-piriform foramen. The white arrowhead indicates the pudendal nerve. GM – gluteus medius muscle, GT – greater trochanter, IG – inferior gemellus, IT – ischial tuberosity, OI – obturator internus, PM – piriformis muscle, QF – quadratus femoris, SN – sciatic nerve, SG – superior gemellus, STL – sacrotuberous ligament.
Figure 2
Figure 2
The common peroneal nerve running through the piriformis muscle. The white arrowheads indicate two parts of the piriformis with the common peroneal nerve running between them. The black arrowhead indicates a tendon of the superior gemellus muscle, fused with the piriformis tendon. GM – gluteus medius muscle, GMx – gluteus maximus muscle, IG – inferior gemellus, IT – ischial tuberosity, P – common peroneal nerve, PM – piriformis muscle, QF – quadratus femoris, SG – superior gemellus, T – tibial part of the sciatic nerve.
Figure 3
Figure 3
Fusion of the piriformis and the gluteus medius muscle. The white arrowhead indicates the superior gluteal vessels, running between fibres of the two fused muscles. GM&PM – fusion of the two muscles, GT – greater trochanter, SN – sciatic nerve.
Figure 4
Figure 4
The common peroneal nerve running through the suprapiriform foramen. GM – gluteus medius muscle, P – common peroneal nerve, PM – piriformis muscle, T – tibial part of the sciatic nerve.
Figure 5
Figure 5
Comparison of dispersion of selected variables in the first group (a typical morphology of the piriformis) and in the second group (with anatomical variations).
Figure 6
Figure 6
Comparison of dispersion of selected variables in the male limbs group (1) and in the female limbs group (2).

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