New landmarks for the anterior approach to the sciatic nerve block: imaging and clinical study

In this study, we assessed the reliability of the inguinal crease and femoral artery as anatomic landmarks for the anterior approach to the sciatic nerve and determined the optimal position of the leg during this approach. An imaging study was conducted before the clinical study. The sciatic nerve was located twice in 20 patients undergoing ankle or foot surgery, once with the leg in the neutral position and once with the leg in the externally rotated position. The patient was lying supine. A 22-gauge, 150-mm insulated b-beveled needle connected to a nerve stimulator was inserted 2.5 cm distal to the inguinal crease and 2.5 cm medial to the femoral artery and was directed posteriorly and laterally with a 10 degrees -15 degrees angle relative to the vertical plane. The sciatic nerve was located in all patients at a depth of 10.6 +/- 1.8 cm when the leg was in the neutral position and 10.4 +/- 1.5 cm when the leg was in the externally rotated position (not significant). In the neutral position and in the externally rotated position, the time needed to identify anatomic landmarks was 28 +/- 15 s and 26 +/- 14 s, respectively (not significant), and the time needed to locate the sciatic nerve was 79 +/- 53 s and 46 +/- 25 s (P < 0.006), respectively. We conclude that the inguinal crease and femoral artery are reliable and effective anatomic landmarks for the anterior approach to the sciatic nerve and that the optimal position of the leg is the externally rotated position.

This new anterior approach to the sciatic nerve using the inguinal crease and femoral artery as landmarks is an easy and reliable technique.