Anatomical variations in the course of the sciatic nerve among ugandans.

Abstract

BACKGROUND: The sciatic nerve is the biggest nerve in the body and supplies most of the lower limb except the anterior compartment of the thigh and the skin of the medical aspect of the leg. It is commonly injured during the application of intragluteal injections. OBJECTIVES: To determine the course of the sciatic nerve in the thigh and how it varies in different individuals. METHODS: This was a descriptive cross sectional study which was carried out in the anatomy dissection laboratory, Makerere medical school and the mortuary at mulago hospital. RESULTS: 80 Limbs were dissected among which 56 (70%) were male and 24 (30%) were female. The height of the specimens ranged from 145 cm to 182 cm. In all cases the nerve was located in the lower medical quadrant of the gluteal region. The nerve entered the gluteal region in an intact state in 62 (77.5%) individuals and in a bifurcated state in 18 (22.5%) individuals. Among the 62 intact cases, the level of bifurcation of the nerve was found at an average vertical distance above the transverse popliteal crease of 8.5cm. Height of an individual and level of bifurcation of the nurve are not related. The common peroneal nerve passed above and the tibial nerve below the superior piriformis in 2 cases (2.5%) and the common peroneal nerve pierced piriformis and the tibial nerve passed below piriformis in 1 case (1.3%). In 4(5%) cases, the nerve which entered the gluteal region. 89.4% of sciatic nerve main trunks bifurcate between 3.8 and 12 cm above the transverse popliteal crease. Height of an individual is independent of the level of bifurcation of the nerve above the transverse popliteal crease. The sciatic nerve enters the gluteal region when intact in 77.5 % and when bifurcated and fuses again in 5% of individuals. RECOMMENDATIONS: Health workers should avoid the lower medial quadrant when administering intragureal injections and also put sciatic nurve variations into consideration when investigating sciatica. Popliteal block of the sciatic nerve above the transverse popliteal crease should be done above 12 cm.