Lateral or Posterior Popliteal Approach for Sciatic Nerve Block: Difference is Related to the Anatomy

To the Editor: March and colleagues (1) comparing single- and double-injection techniques for blockade of the sciatic nerve block via a posterior popliteal approach, concluded that double-nerve stimulation resulted in similar onset time and overall success rate when compared with that after single-nerve stimulation. In the double-injection group, they located both common peroneal and tibial nerve, whereas in the single-injection group they preferentially elicited foot inversion, interpreting this motor response to reflect needle proximity to both sciatic nerve trunks (2). Our group has extensive experience providing regional anesthesia for outpatients undergoing foot surgery (3). We recently showed that, when using a lateral popliteal sciatic nerve block, a single injection targeting the tibial nerve is more effective than a single injection targeting the peroneal nerve and is also as effective as a double injection of both branches of the sciatic nerve (4). We believe that results from March's work lend further support for our results, even when the different drugs and dosages used are taken into account. When a double-injection procedure is employed, the success rates after the lateral or posterior approaches are similar (respectively, 94% vs 87%) whereas a single-injection technique yields similar or even better results only if it is performed via a lateral approach and it is targeted at the tibial branch of the sciatic nerve (success rate: lateral 94% vs posterior 77%). Considering the anatomy of the sciatic nerve at the popliteal level (5), targeting the tibial nerve via a lateral popliteal approach will likely result in injecting local anesthetic within the adventitia that envelops both branches of the sciatic nerve (4). On the other hand, the same single injection technique performed via a posterior approach will not assure that local anesthetic is injected within the tibial and peroneal common perineural space. Stefano Palmisani Department of Anesthesiology and Intensive Care Medicine Sant'Andrea Hospital University of Rome La Sapienza [email protected] Paolo Ronconi, MD Foot Medical Hospital Roberto Alberto De Blasi, MD Roberto Arcioni, MD Department of Anesthesiology and Intensive Care Medicine Sant'Andrea Hospital University of Rome La Sapienza Rome, Italy