Anatomy and Exposures of Spinal Nerves

Abstract

The sciatic nervesciatic nervehas two major components: the tibial nervetibial nervefrom the anterior divisionanterior divisionof L4–S3 and the common peroneal nervecommon peroneal nervefrom the posterior divisionposterior divisionof L4–S2. It forms in front of the piriformispiriformismuscle in the pelvis and exits the greater sciatic foramen usually below the piriformis, occasionally within the muscle, and then enters the thigh between the ischial tuberosity and the greater trochanter. Structures deep to the sciatic nerve from cranial to caudal are the gemellus superiorgemellus superior, obturator internusobturator internus, gemellus inferiorgemellus inferior, quadratus femorisquadratus femoris, and adductor magnusadductor magnus. Structures superficial to the sciatic nerveinclude, in the buttock: gluteus maximusgluteus maximus, and in the thigh: the long head of biceps femorisbiceps femoriscrosses the nerve from medial to lateral. The nerve supplies the hamstrings—biceps femoris, semimembranosussemimembranosus, and semitendinosussemitendinosus—as well as the ischial part of adductor magnus. The nerve ends by splitting into tibial and common peroneal (common fibular) components in the lower thigh.