Levels of Bifurcation of the Sciatic Nerve as Seen at Mulago Hospital

Abstract

Background: The sciatic nerve is comprised of the tibial, and the common peroneal nerves, and supplies the posterior thigh, the leg and foot. Its injury commonly results in 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 anatomy of the nerve. The objective of this 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 dissection laboratory faculty of Medicine, Makerere University and Mulago Hospital mortuary. Eighty cadavers were dissected in the gluteal region and posterior thigh to establish the level of bifurcation of the nerve above the transverse popliteal crease, and this distance was measured.

Results: A total of 80 left lower limbs were dissected including 56 males and 24 females. Specimen height ranged between 145 and 182 cm with a mean of 162.8cm.The nerve bifurcated in the gluteal region and posterior thigh in 77.5% cases and in the pelvis in 22.5% cases. For the 77.5% nerves that bifurcated beyond the pelvis, the level of bifurcation ranged between 3.8 and 32.5 cm, most of the bifurcations occurred between 3.8-12cm above transverse popliteal crease. In four of the nerves that entered the gluteal region after bifurcation, the nerve reunited before final bifurcation occurred in the thigh.

Conclusions: The sciatic nerve bifurcation is very variable and adequate appreciation of these variations is essential. It should be noted that more than 22% of all the nerves leave the pelvis as two separate nerve which means the sciatic nerve trunk can not be traced or used for anesthetic block in the gluteal region or thigh. Only 77.5% of individuals have a sciatic nerve in the gluteal region and thigh, and even within this group of people, the vertical distance of bifurcation ranges between 3.8-32.5cm.

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