The posterior approach to the sciatic nerve in the popliteal fossa: a comparison of single- versus double-injection technique.

We compared single-injection and double-injection of the sciatic nerve with nerve stimulation in the posterior popliteal approach using mepivacaine 1% in a prospective, randomized and single-blind study to evaluate effectiveness, delay of onset, and complications in patients undergoing foot and ankle surgery. In the single-injection group (Group S, n = 30), 25 mL of mepivacaine 1% was administered after eliciting foot inversion or plantar flexion. In the double-injection group (Group D, n = 30), 12.5 mL of the solution was injected after eversion or dorsiflexion and 12.5 mL after plantar flexion of the foot. Mean differences (SD) between the two groups from onset time to complete sensory block were not significant (21.9 [14.2] min vs 22.1 [13.8] min) except for the superficial peroneal nerve block (18 [13] min vs 11.4 [7.5] min, Group S and D, respectively; P < 0.05) and, in Group D, between the superficial peroneal and tibial nerve blocks (11.4 [7.5] min vs 22.3 [11.3] min, respectively; P < 0.05). Complete analgesia was achieved in 77% of Group S patients and in 87% of Group D (P = 0.22). Complete analgesia of the deep peroneal nerve was achieved in 80% and 97% in Group S and D, respectively; P < 0.05. There were more paresthesias during block procedure in Group D (17% vs 40%) (P < 0.05). We conclude that double-nerve stimulation of the sciatic nerve gives similar complete onset times and overall success rate to single-nerve stimulation and more paresthesias during block performance.