Levels of Bifurcation of the Sciatic Nerve among Ugandans at School of Biomedical Sciences Makerere and Mulago Hospital Uganda

Abstract

Background: The sciatic nerve is derived from the lumbo-sacral plexus, It is the thickest nerve in the whole body, it exits the gluteal region through the lower part of the greater sciatic foramen, it is the main innervator of the posterior thigh, the leg and foot, it usually ends halfway down the back of the thigh by dividing into the tibial and common peroneal nerves, and these terminal branches supply the leg and foot. The position of division of this nerve varies, it may occur within the pelvis, gluteal region, upper and ,mid thigh, and distal thigh ,Its injury if it involves the whole nerve, may lead to loss of sensation, in posterior thigh, whole leg and foot, with loss of function of all muscles in posterior thigh, whole leg and the foot. And this results into failure to dorsiflex the foot a condition referred to as foot drop. The level of bifurcation of the sciatic nerve above the transverse popliteal crease is useful during sciatic nerve block, hence the need for healthcare workers to have adequate appreciation of the applied anatomy of the nerve. The main objective of the study was to determine the level of bifurcation of the sciatic nerve above the transverse popliteal crease among Ugandans at Mulago Hospital Complex.

Methods: This was a cross-sectional descriptive study conducted at the Department of Anatomy, School of Biomedical sciences, Makerere University and Mulago Hospital mortuary. Eighty adult cadavers were dissected in the gluteal region and posterior thigh to establish the level of bifurcation of the sciatic nerve above the transverse popliteal crease, and the distance from the crease was measured in cm using a caliper calibrated in millimeters.

Results: Eighty left lower limbs of 56 male and 24 female adult cadavers were dissected to expose the sciatic nerve one side of the body was dissected to control for left to right variations, however in another study, the variations on two sides would be compared.., The heights of the cadavers ranged from 145 to 182 cm with a mean of 162.8 cm. The nerves bifurcated in the gluteal region and posterior thigh in 62 cadavers (77.5%) and 18 in the pelvis (22.5%). Of the 62 nerves that bifurcated higher in the pelvis, the level of bifurcation ranged between 3.8 and 32.5 cm but most of the bifurcations occurred between 3.8 and 12 cm above transverse popliteal crease. In four of the nerves that exited the gluteal region after bifurcation, the nerves reunited before the final bifurcation occurred in the thigh.

Conclusions: The Bifurcation of the sciatic nerve occurs at variable distances from the transverse popliteal crease and appreciation of these variations is essential. More than 22% of all nerves leave the pelvis as two separate nerves and therefore the sciatic nerve trunk cannot be wholly traced or used for anesthetic block in the gluteal region or thigh for procedures in the leg and foot. Only 62 individuals (77.5%) had sciatic nerves in the gluteal region and thigh, and within this group, the vertical distance of bifurcation ranged between 3.8 and 32.5 cm transverse popliteal crease.