Anatomical variation in bifurcation and trifurcations of sciatic nerve and its clinical implications: in selected university in Ethiopia

Abstract

BackgroundThe Sciatic nerve is the widest nerve of the body. It consists of two components, namely: the tibia and the common peroneal components derived from the ventral rami of L4 to S3 spinal nerves of the lumbosacral plexus. It exits the pelvis through the greater sciatic foramen below the Piriformis muscle and descends between the greater trochanter of the femur and ischial tuberosity of the pelvis to the knee. The purpose of this study is to identify the course and variations in branching pattern of the sciatic nerve which may lead to various clinical manifestations.MethodsTwenty-eight formalin fixed cadavers comprising of 56 lower limbs are used for this study, of which six specimens were female cadavers. Dissection of gluteal region and posterior compartment of the thigh was done to expose the sciatic nerve. Variations in the sciatic nerve anatomy; their relationship to Piriformis muscle and a point of bifurcation and trifurcation were noted and recorded.ResultsForty-two lower limbs (75 %) showed normal anatomy of sciatic nerve. Fourteen regions (25 %) showed variations in the sciatic nerve, of which six regions (11 %) showed a variation of the sciatic nerve in relation to Piriformis muscle, three regions (5 %) showed trifurcation of the sciatic nerve and five regions (9 %) showed variation in the origin of the sural nerve.ConclusionThe knowledge regarding the level of division and distribution of the sciatic nerve and its location is of great importance. The sciatic nerve is frequently involved in daily medical practice of neurology, orthopedics, rehabilitation and anesthesia. Its long course makes it vulnerable to nerve injury. Even in this era the cadaver is the best means to study anatomy. It emphasizes proper clinical implications, for the surgeons to practice efficient surgical recombination and avoid errors.

Non-formation of the main trunk of the sciatic nerve and unusual relationships to the piriformis muscle

“…A recent study [11] reports a similar incidence of the same variation -9% of the sample. The relative portion of similar Type 2 variations is as low as 2,5% in a study conducted on fetuses (12).…”

Posterior Surgical Approach to the Knee

“…[9][10][11][12] For most, the sciatic bifurcation into the tibial and common peroneal nerve is localized near the apex of the popliteal fossa. 13 However, this bifurcation can occur at different levels of the limb, oftentimes higher than the recorded height. 13 In rare cases where the division of the sciatic nerve is found lower, a trifurcation can occur.…”

“…13 However, this bifurcation can occur at different levels of the limb, oftentimes higher than the recorded height. 13 In rare cases where the division of the sciatic nerve is found lower, a trifurcation can occur. 14,15 The origin of the sural nerve can also vary, either emerging from the tibial nerve or the common peroneal nerve.…”

“…14,15 The origin of the sural nerve can also vary, either emerging from the tibial nerve or the common peroneal nerve. 13 Lastly, the popliteal artery divides at the same level as the inferior border of the popliteus in 92.2% of patients. However, in 7.8%, the origin is either higher than normal or a trifurcation.…”

“…16 Knowledge of these anatomic variants is important to avoid complications with this approach. 13 As previously mentioned, the main limitations of this procedure are the risks to the neurovascular structures within the knee. One must proceed cautiously and meticulously during dissection to accurately isolate and retract the various structures.…”