Variations of Sciatic Nerve Bifurcation: A Study

Background: The sciatic nerve (SN) is the thickest nerve in the body. It is formed in the pelvis from the ventral rami of the fourth lumbar to the third sacral spinal nerves and leaves the pelvis via the greater sciatic foramen below pyriformis and divides into Common Peroneal nerve (CPN) and Tibial nerve (TN) at the superior angle of popliteal fossa. High division of the sciatic nerve is the most common variation wherein the TN and the CPN may leave the pelvis through different routes. Such variations may lead to compression of the nerve, non discogenic sciatica, pyriform syndrome and also to incomplete sciatic nerve block. Knowledge regarding this may help the surgeon to plan for various surgical intervention pertaining to the gluteal region. Aim: To study the course and division of sciatic nerve. Methodology: The study was conducted in the department of Anatomy, Subbaiah Institute of Medical Sciences over a period of 5 years. 70 lower extremities of 35 cadavers of both sexes were studied to see the variations in sciatic nerve bifurcation. Beaton and Anson classification has been followed for the classification of division of Sciatic nerve. Results: In our study on 70 lower extremities of 35 cadavers, we observed 6 (8.6%) high division of SN. Among these, 2 (2.9%) lower extremities showed high division in the back of thigh and 4 (5.7%) showed within the pelvis. The remaining 64 (91.4%) lower extremities showed the division outside the pelvis. Conclusion: Knowledge regarding the variation in the level of division of the sciatic nerve and its pelvic exit is of utmost importance in order to prevent inadvertent injury to the nerve during various surgical interventions in the gluteal region