Anatomical and Ultrasound Study of the Mid-Femoral Sciatic Nerve and Its Division

Abstract

OBJECTIVES Anatomical variations of the sciatic nerve were supposed as potential causes for incomplete blocks at the level of the popliteal fossa. Therefore, we aimed to conduct an anatomical and ultrasound survey of the mid-femoral sciatic nerve and its division. BACKGROUND A regional block of the sciatic nerve is a procedure for analgesia and anaesthesia of the lower extremity. Various approaches to the sciatic nerve are used in clinical practice. However, the sciatic nerve demonstrates several variations regarding its topography and division. MATERIALS AND METHODS The anatomical study included twenty lower limbs of ten adult cadavers. The ultrasound study involved ten upper legs of five healthy volunteers RESULTS The sciatic nerve was found distally to the piriformis muscle in all our cadaveric specimens. It was divided into two major branches (common peroneal nerve and tibial nerve) at a mean distance of 68.1 ± 19.3 mm above the popliteal crease. The observed distances ranged widely from 35 to 113 mm. The mid-femoral sciatic nerve and its division were entirely revealed using ultrasound in all volunteers. CONCLUSION The sciatic nerve presents significant anatomical variations, which may cause an incomplete block. Understanding ultrasound anatomy and ultrasound appearance of the sciatic nerve is essential for performing ultrasound-guided sciatic blocks.