A Comparison of the Posterior versus Lateral Approaches to the Block of the Sciatic Nerve in the Popliteal Fossa

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Abstract
Background: The main disadvantage of the posterior approach to the block of the sciatic nerve in the popliteal fossa (popliteal block [PB]) is the need to place the patient in the prone position. In this study, the authors examined the clinical utility of a recently described lateral approach to PB that is performed with the patient in the supine position, and they compared its ability to provide reliable surgical anesthesia with that of the posterior approach. Methods: Fifty patients undergoing surgery of a lower extremity were randomized to receive the PB using either the lateral (n=25) or the posterior approach (n=25). With both techniques, 40 ml 1.5% alkalinized mepivacaine with 1:200,000 epinephrine were injected on successful nerve localization using low current output nerve stimulation. Results: There were no differences in American Society of Anesthesiologists physical status or demographic data between the groups (ASA status, I-III; mean age, 50+/-15 yr; 27 men, 23 women). All patients had good intraoperative analgesia, except one in the lateral group, who reported pain outside the distribution of the sciatic nerve. Conclusions: Although blockade using the lateral approach took longer to accomplish, both techniques resulted in clinically acceptable anesthesia in the distribution of the sciatic nerve.