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INTRODUCTION

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Distal sciatic nerve block (popliteal fossa block) is a very clinically valuable technique that results in anesthesia of the calf, tibia, fibula, ankle, and foot.1,2,3 The sciatic nerve can be approached from either the posterior approach, described by Duane Keith Rorie,3 or the lateral approach, described by Jerry Vloka.1 Both approaches provide equivalent anesthesia and are suitable for catheter placement. Overall, however, the posterior approach is easier for trainees to learn.1,2

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Popliteal fossa block performed with long-acting local anesthetics such as ropivacaine can provide 12–24 hours of analgesia after foot surgery.3,4

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When used as a sole technique popliteal fossa block provides excellent anesthesia and postoperative analgesia, allows use of a calf tourniquet, and avoids the disadvantages of neuraxial blockade.5

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Analgesia with popliteal fossa blocks lasts significantly longer than with ankle blocks. For instance, David H. McLeod found that lateral popliteal fossa block with 0.5% bupivacaine lasted 18 hours when compared with ankle block, which lasted only 6.2 hours.6 Popliteal fossa block has also been used as an effective analgesic technique in children.7 In a study of the efficacy of the popliteal sciatic nerve blockade (0.75 mL/kg of ropivacaine 0.2%) after foot and ankle surgery, 19 of 20 children required no analgesic agents during the first 8–12 hours postoperatively.

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Indications and Contraindications

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The popliteal block is one of the most commonly used techniques in regional anesthesia practice. Some common indications include corrective foot surgery, foot debridement, short saphenous vein stripping, repair of the Achilles tendon, and others.8 As opposed to the more proximal block of the sciatic nerve, popliteal fossa block anesthetizes the leg distal to the hamstring muscles, allowing patients to retain knee flexion.9,10

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Functional Anatomy

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The sciatic nerve consists of two separate nerve trunks: the tibial and common peroneal nerves. A common paraneural sheath envelops these two nerves from their origin in the pelvis, which is distinctly separate from the epineurium of each nerve.11 Studies utilizing ultrasound imaging have shown that injecting local anesthetic within this sheath consistently gives a rapid onset, safe, and effective block.12 This is not considered to be an intraneural injection as long as the epineurium of the individual nerves is not breached.13,14 As the sciatic nerve descends toward the knee, the two components eventually diverge just proximal to the popliteal fossa, giving rise to the tibial and common peroneal nerves (Figure 82E–1). This division of the sciatic nerve usually occurs between 50 and 120 mm proximal to the popliteal fossa crease.15,16 Following its divergence from the sciatic nerve, the common peroneal nerve continues its path laterally and descends along the head and neck of the fibula. Its major branches in this region are ...

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