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

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.