[Simplified sciatic nerve approach by the posterior route at the median gluteus-femoral sulcus region, with a neurostimulator.].

Background And Objectives: The sciatic nerve may be blocked by several routes, all of them with advantages and disadvantages. It is the largest human nerve in diameter and length, being the prolongation of the upper sacral plexus fascicle (L4, L5, S2 and S3). It leaves the pelvis through the foramen ischiadicum majus, passing below the piriform muscle and going down between the greater trochanter and the ischial tuberosity, continuing along the femoral dorsum, anterior to biceps femoris and semitendinous muscles, to the lower femoral third, where it is divided in two major branches called tibial and common fibular nerves. It becomes superficial at the lower border of the gluteus maximus muscle. Based on this anatomic description, we developed a posterior approach with the following advantages: easy identification of the surface anatomy, superficial level of the nerve at this location; and less discomfort to patients since a 5 cm needle may be used.

Methods: Seventeen ASA I - III patients aged 21 to 79 years, weighing 55 to 90 kg, undergoing leg or foot surgery were studied. After monitoring, patients were placed in the prone position and blockade was performed at the middle point of the sulcus gluteus (skin fold between nates and posterior thigh), with the aid of a neurostimulator, using 1% plain lidocaine (300 mg). Onset time, blockade performing time, and tibial, common fibular and cutaneous femoris posterior nerves anesthesia were evaluated. Saphenous nerve was also blocked with 5 ml of 1% lidocaine whenever needed.

Results: Adequate anesthesia was obtained in all cases. There was no patient with cutaneous femoris posterior nerve anesthesia. Blockade performing time was 8.58 +/- 5.71 min. Onset time was 5.88 +/- 1.6 min. Sensory and motor block duration was 4.05 +/- 1.1 and 2.9 +/- 0.8 hours, respectively.

Conclusions: This new approach is effective and easy. However, it is not indicated when the cutaneous femoris posterior nerve anesthesia is necessary.