Novel variations in the anatomical relationship between the piriformis muscle and sciatic nerve: a cadaveric study (LB2)

Abstract

The goal of this study is to assess variations in the anatomical relationship between the piriformis muscle and sciatic nerve in a cadaveric population. Currently, Beaton and Anson’s 1937 classification of piriformis‐sciatic arrangements is widely accepted and used for clinical evaluation and diagnosis of Piriformis Syndrome—a dynamic sciatic nerve impingement by the piriformis muscle. This study (n=164 limbs) revealed two clinically important differences to Beaton and Anson’s original findings. First, the Type “B” classification was observed in 18.3% of the cases, representing a 63.9% increase from Beaton and Anson’s original report. Additionally, two Type “B” subsets with potential clinical consequences were observed. Type “B2” included a vascular component, wherein the inferior gluteal artery and vein coursed between the common fibular and tibial divisions of the sciatic nerve (4.3% of total cases). Type “B3” included an additional nerve component, wherein the inferior gluteal nerve coursed between the piriformis muscle and adjacent to the common fibular division, to reach the gluteus maximus muscle (1.0% of total cases). Collectively, these observations expand the current classification of piriformis‐sciatic arrangement, and carry clinical significance for the evaluation and treatment of Piriformis Syndrome.Grant Funding Source: n/a