A New Anterior Approach to the Sciatic Nerve Block

Background: Although several anterior approaches to sciatic nerve block have been described, they are used infrequently. The authors describe a new anterior approach that allows access to the sciatic nerve with the patient in the supine position. Method: Sciatic nerve blocks were performed in 22 patients. A line was drawn between the inferior border of the anterosuperior iliac spine and the superior angle of the pubic symphysis tubercle. Next, a perpendicular line bisecting the initial line was drawn and extended 8 cm caudad. The needle was inserted perpendicularly to the skin, and the sciatic nerve was identified at a depth of 10.5 cm (9.5–13.5 cm; median and range) using a nerve stimulator and a 15-cm b-beveled insulated needle. After appropriate localization, either 30 ml mepivacaine, 1.5% (group 1 5 knee arthroscopy; n 5 16), or 15 ml mepivacaine, 1.5%, plus 15 ml ropivacaine, 0.75%, (group 2 5 other procedures; n 5 6) was injected. Results: Appropriate landmarks were determined within 1.3 min (0.5–2.0 min). The sciatic nerve was identified in all patients within 2.5 min (1.2–5 min), starting from the beginning of the appropriate landmark determination to the stimulation of its common peroneal nerve component in 13 cases and its tibial nerve component in 9 cases. A complete sensory block in the distribution of both the common peroneal nerve component and the tibial nerve component was obtained within 15 min (5–30 min). A shorter onset was observed in patients who received mepivacaine alone compared with those who received a mixture of mepivacaine plus ropivacaine (10 min [5–25 min] vs. 20 min [10–30 min]; P < 0.05). Recovery time was 4.6 h (2.5–5.5 h) after mepivacaine administration. The addition of ropivacaine produced a block of a much longer duration 13.8 h (5.2–23.6 h); P < 0.05. No complications were observed. Conclusions: This approach represents an easy and reliable anterior technique for performing sciatic nerve blocks. (