The anterior approach to the sciatic nerve has been described for use in patients who can not be positioned in the lateral decubitus position [49,50]. Two important landmarks for this block include: the inguinal ligament and the greater trochanter of the femur. Determination of the site of needle insertion requires that two lines be drawn: 1) one line parallel to the inguinal ligament passing over the greater trochanter, and 2) the second line parallel to the major axis of the body passing over the union of the medial one third with the lateral two thirds of the inguinal ligament (Figure 5). The needle insertion site corresponds to the intersection of the two lines. Several attempts have been made to simplify the location of the puncture site, but they applicability to young children remains questionable [51,52].

The needle is inserted almost perpendicularly to the skin toward the medial edge of the femur (supposedly the lesser trochanter of the femur) until twitches are elicited in the foot. This technique is consistently more difficult than the posterior approach, can result in inadvertent puncture of the femoral vessels and should be reserved for patients in whom that posterior approach can not be used.


                             Figure 5. Proximal anterior approach to the sciatic nerve
                             1. Anterior superior iliac spine
                             2. Pubic spine (or tubercle)
                             3. Greater trochanter of the femur
                             4. Site of puncture
                             5. Sciatic nerve