A Subgluteal Approach to the Sciatic Nerve in Adults at 10 cm From the Midline

Abstract

In 2003 we introduced the concept of a sciatic nerve block performed in the midgluteal area at a fixed distance from the midline in all adults regardless of gender and/or body size. The anatomic basis for that study suggested that a subgluteal block could also be accomplished in a similar fashion. After informed consent, 20 patients were prospectively recruited. Patients were positioned in lateral decubitus. The needle insertion site was located in the subgluteal fold at 10 cm from the midline. The needle was advanced parallel to the midline until a sciatic nerve response was elicited. With a visible response at 0.5 mA, 30 mL 1.5% mepivacaine plus 1:200,000 epinephrine was slowly injected. Sensory anesthesia was tested on the plantar and dorsal aspects of the foot as well as the posterior thigh. Residents performed all blocks. The approach was 100% successful in locating the sciatic nerve with 3 attempts or less from a site located 10 cm from the midline. The block provided successful surgical anesthesia in 90% of the cases; 2 cases required local anesthetic supplementation. Only 3 patients developed anesthesia of the posterior thigh within 30 minutes of injection. This report shows that a sciatic nerve block can be performed in the subgluteal area at 10 cm from the midline in adult patients of both sexes and various sizes. Anesthesia of the posterior thigh is not consistently accomplished with this approach.