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Review
. 2020 Nov 17;12(11):e11531.
doi: 10.7759/cureus.11531.

Sciatic Nerve Variants and the Piriformis Muscle: A Systematic Review and Meta-Analysis

Frideriki Poutoglidou  1 , Maria Piagkou  2 , Trifon Totlis  3 , Maria Tzika  4 , Konstantinos Natsis  4
Affiliations
Review

Sciatic Nerve Variants and the Piriformis Muscle: A Systematic Review and Meta-Analysis

Frideriki Poutoglidou et al. Cureus. .

Abstract

The present systematic review and meta-analysis provides a comprehensive assessment of the sciatic nerve (SN) variants relative to the piriformis muscle (PM) and compares those variants' prevalence among different geographical populations with respect to gender and laterality. A database search was conducted to identify cadaveric studies pertinent to SN variants relative to the PM. A total of 44 articles were included. The typical morphological pattern (type A, with the SN passing undivided below the PM) was found to be the most common variant, with 90% pooled prevalence. SN variants were more common among East Asians, with a 31% pooled prevalence of total variants. No significant differences were established with respect to gender and laterality. In greater than 10% of the population, the SN coursed through or above piriformis. Patients' epidemiological characteristics may predispose them to certain variants. The common peroneal nerve (CPN) is more susceptible to injury during a total hip arthroplasty or a hip arthroscopy where anomalies are encountered. As anatomical variants are commonly associated with piriformis syndrome, they should always be considered during diagnosis and treatment.

Keywords: abnormality; anatomy; anomaly; piriformis muscle; sciatic nerve; variation.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. The Beaton and Anson classification system (1937)*
*[3] Type A: typical morphological pattern, the SN passes below the PM undivided. Type B: the CPN exits through the PM and the TN exits below the PM. Type C: the CPN exits above the PM and the TN and below the PM. Type D: the SN exits through the PM, as a single trunk. Type E: the CPN exits above the PM and the TN through the PM. Type F: the SN passes undivided above the PM SN: sciatic nerve; PM: piriformis muscle; CPN: common peroneal nerve; TN: tibial nerve
Figure 2
Figure 2. PRISMA flowchart summarizing the selection process
PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses
Figure 3
Figure 3. Prevalence of anatomic variations of the SN relative to the PM
SN: sciatic nerve; PM: piriformis muscle
See this image and copyright information in PMC

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