[Lateral popliteal block: a modification of anatomical references].
OBJECTIVE: To study the efficacy of a lateral approach in performing a sciatic nerve block at the popliteal fossa using modified anatomical references: the intersection of the groove between the lateral vastus and biceps femoris muscles and the axis of the femur, which passes through the upper vertex of the popliteal fossa. PATIENTS AND METHOD: The described lateral approach was used in a series of 50 patients scheduled for foot surgery. We located the nerve by stimulation and infused 40 mL of 1.5% mepivacaine. Several technical features, efficacy and complications were analyzed. RESULTS: The mean patient age was 55 years, mean weight was 67 +/- 12.6 Kg, and mean height was 159.8 +/- 6.7 cm. Only 1 puncture was necessary in 90% of the cases; 2 punctures were needed in 10%. The point of puncture was proximal to the lateral condyle of the femur at a mean 9.1 +/- 2.1 cm. Depth ranged from 3.8 to 9 cm. The mean latency time to onset of the surgical block was 28.3 +/- 8 minutes. The block was considered excellent in 42 cases and adequate in 6; the technique failed in 2 cases. No major complications were observed. CONCLUSIONS: The proposed approach is easy to implement, involves no remarkable complications, and is particularly useful in patients who have difficulty taking a prone decubitus position.