Topography of the sciatic nerve's fibres in regard of clinical use.

72 sciatic nerves were investigated from the level of the sciatic tuberosity to the branching off of the nerves for the posterior thigh muscles. The area of the cross section has a mean value of about 72 mm2. Almost 1/3 of it belongs to the peroneal component. The bundles for the hamstring muscles occupy about 13% of the tibial component; mostly they are situated slightly anterior to the medial margin of the nerve. The bundles for the short head of the biceps muscle of the femur occupy about 11% of the peroneal component; they are situated slightly anterior to the lateral margin of the nerve. The bundles for the hamstring muscles exchange fibres with other fascicles in more than 60% of the specimens, whereas the bundles for the short biceps head do so in less than 25%.