A new posterior approach to the sciatic nerve block: A prospective, randomized comparison with the classic posterior approach

To evaluate the efficacy and acceptance of a new posterior subgluteus appro ach to the sciatic nerve, as compared with the classic posterior approach, 128 patients undergoing foot orthopedic procedures were randomly allocated to receive either the classic posterior sciatic nerve block (Group Labat, n = 64) or a modified subgluteus posterior approach (Group subgluteus, ii 64 ). All blocks were performed with the use of a nerve stimulator (stimulatio n frequency, 2 Hz; intensity, 1-0.5 mA). In Group subgluteus, a line was dr awn from the greater trochanter to the ischial tuberosity; then, from the m idpoint of this line, a second line was drawn perpendicularly and extended caudally for 4 cm. The end of this line represented the needle entry. In bo th groups, a proper sciatic stimulation was elicited at 0.5 mA; then 20 mL of 0.75% ropivacaine was injected. The time from needle insertion to succes sful sciatic nerve stimulation was 60 s (range, 10-180 s) with the Labat's approach and 32 s (range, 5-120 s) with the new subgluteus approach (P = 0. 0005). The depth of appropriate sciatic stimulation was 45 +/- 13 mm (mean +/- SD) after 2 (range, 1-7) needle redirections in Group subgluteus and 67 +/- 12 mm. after 4 (range, 1-10) needle redirections in Group Labat (P = 0 .0001 and P = 0.00001, respectively). The failure rate was similar in both groups. Severe discomfort during the procedure was less frequent and accept ance better in Group subgluteus (5 patients [8%] and 60 patients [94%], res pectively) than in Group Labat (20 patients [31%] and 49 patients [77%], re spectively) (P = 0.0005 and P = 0.005, respectively). We conclude that this new subgluteus posterior approach to the sciatic nerve is an easy and reli able technique and can be considered an effective alternative to the more t raditional Labat's approach.