Popliteal Sciatic Nerve Block

The popliteal approach to the sciatic nerve and its two division branches is the most suitable technique of sciatic nerve block. It is recommended for all types of surgery on the leg and foot and requires only small amounts of local anesthetics. There are virtually no contraindications to this block procedure, the quality of analgesia is remarkably high, and it lasts longer than the duration of any other conduction block performed with the same local anesthetic (i.e., usually more than 12 hours and occasionally more than 18 hours).^[237] The technique is performed with the child in the prone or, preferably, the semiprone position, resting on the nonoperated side.^[236] The landmarks are the borders of the popliteal fossa: the tendon of the biceps femoris muscle laterally and the tendons of the semimembranosus and semitendinosus muscles medially ( Fig. 45-14 ). The site of puncture lies close to the summit of the popliteal fossa, approximately 1 cm below this summit and 0.5 cm lateral to the bisecting line of its upper angle (to avoid puncturing the popliteal artery). Finger palpation of the upper part of the popliteal fossa can easily identify a dimple, at the center of which the block needle is introduced. The needle is inserted cephalad at a 45- to 60-degree angle to the skin until twitches are elicited in the foot. The sciatic nerve and its division branches lie below the popliteal membrane, the piercing of which can be identified by a characteristic click, which can even be sought by means of an LOR technique.

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Figure 45-14 Popliteal sciatic nerve block, showing the tendon of the biceps femoris (1) and tendons of the semimembranosus and semitendinosus muscles (2).