Clinical Significance of Pathophysiology in Piriformis Syndrome Due to Multiple Variations in the Deep Gluteal Region

Abstract

A relationship between the piriformis muscle and the sciatic nerve, which is observed to be unusual has been suggested to be a cause of piriformis syndrome. During dissection of a male cadaver, several anatomical variations were encountered. These variations consist of atypical organization of the sacral plexus, unusual origins, trajectories of common fibular, tibial, and inferior gluteal nerves. It is also observed that the presence of a common tendon formed by the deep gluteal muscles (obturator internus, superior gemellus, inferior gemellus, and both piriformis muscles, a duplication of the piriformis muscle) inserts on the greater trochanter of the femur. Additionally, an early division of the sciatic nerve, where a common fibular nerve that runs between the two variant piriformis muscles, and the tibial nerve which is making its way below the inferior piriformis, is also observed. These anatomical variations are found to be bilateral. In these casses the unusual pathway of this sciatic nerve and its relationship with the piriformis may predispose to its impingement at the gluteal region. The prevalence of the piriformis and the sciatic nerve anomalies is 16.2% in surgical cases. Thus, clinicians and surgeons should be aware of the potential complications from these unique variations.