The sciatic nerve may be one solid nerve, or the tibial and common peroneal nerves may be visualized within the sciatic nerve, the tibial nerve located medially and the common peroneal nerve laterally. Occasionally, the tibial and peroneal nerves are two separate nerves as soon as they descend from the sacrosciatic foramen. If the sciatic nerve is one nerve, it may divide into the tibial and common peroneal branches between 4 and 13 cm above the popliteal crease. The posterior approach to sciatic nerve block in the popliteal fossa can be performed with the patient in the prone, lateral, or supine positions. The supine and lateral positions are ideal in the postoperative period, when the patient has difficulty assuming the prone position. The site of needle insertion is at a point 7 cm superior to a crease behind the knee and 1 cm lateral to a line that bissects the superior part of the popliteal fossa. The needle is inserted at a 45°angle and advanced to a depth of 2.5 to 5 cm until a motor response of the foot is elicited with 0.3 to 0.8 mA stimulating current. Elicited inversion or combined inversion/plantar flexion is the preferred motor response. If either one of these motor responses is not elicited easily, then the double injection technique is used. In this technique, two 15-mL injections are performed after identification of the tibial (elicited plantar flexion) and peroneal components (elicited dorsiflexion or eversion) of the sciatic nerve. If the tibial response is elicited first, the needle is moved laterally until the peroneal response is elicited. If the peroneal response is elicited first, the needle is moved medially to elicit the tibial response. A total of 35 to 40 mL mepivacaine, bupivacaine, or ropivacaine, with epinephrine, is used. Although the block is used for intraoperative anesthesia, it is increasingly being performed for postoperative analgesia.
|Original language||English (US)|
|Number of pages||5|
|Journal||Techniques in Regional Anesthesia and Pain Management|
|State||Published - Jan 1 1999|
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine