Sciatic nerve block in the popliteal fossa

The popliteal approach to the sciatic nerve is an excellent choice of analgesia in patients under-going leg and foot surgery. There are virtually no contraindications to this block procedure and the quality of analgesia is remarkably high with a duration lasting longer than that of any other conduc-tion block performed with the same local anesthetic [15]. The sciatic nerve is approached with the child in the prone or, preferably, the semi-prone position with the limb to be blocked lying upper-most [32]. The landmarks are the borders of the popliteal fossa, i.e., the tendon of the biceps femoris muscle laterally and the tendons of the semimembranosus and semitendinosus muscles medially (Figure 8). The site of puncture lies approximately 1 cm below the summit of the popliteal fossa and 0.5 cm lateral to the bisecting line of its upper angle (to avoid puncturing the popliteal artery). In fact, finger palpation of the upper part of the popliteal fossa finds a clearly perceptible dimple at the center of which the block needle will be introduced. The needle is inserted cephalad at a 45-60° angle to the skin until twitches are elicited in the foot. The nerves lie below the popli-teal membrane, the piercing of which can be identified by a characteristic "click", which can even be sought by a loss-of-resistance technique. Recommended volumes of local anesthetic are listed in Table 2 and Table 3. A catheter can easily be introduced for providing long-lasting pain relief, which makes the technique the indication of choice for both intra and postoperative management of clubfoot surgery.




                                      Figure 8. Popliteal approach to the sciatic nerve
                                      1. Tendon of the biceps femoris muscle
                                      2. Tendons of the semimembranosus and semi-
                                           tendinosus muscles