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Distal sciatic nerve block (popliteal fossa block) is a relatively
simple technique that results in reliable surgical anesthesia of the calf,
tibia, fibula, ankle, and foot.1,2 Consequently, this
technique is used primarily for anesthesia or analgesia for foot, ankle, and
lower-leg surgery.3 The sciatic nerve can be approached
from either the posterior approach described by Rorie,3 or
the lateral approach, which eliminates the need to reposition patients in
the supine position.1 With the lateral popliteal fossa
block, patients remain supine for the block and catheter placement, rather
than being prone and then turning supine after the block is placed. Both
approaches provide equivalent surgical anesthesia after nerve
blockade.1 With both approaches, catheters can be inserted
to provide prolonged postoperative analgesia; catheters, however, are more
easily secured in the lateral position. Because of the slower resolution of
neural blockade in the lower extremity, popliteal fossa block performed with
long-acting local anesthetics such as ropivacaine can provide 12–24 hours
of analgesia after foot surgery. The remarkable safety of the block has been
demonstrated in numerous studies.3,4
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Analgesia with lower-extremity blocks typically lasts longer than
analgesia with ankle block. For instance, 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.5 Popliteal
fossa block has also been used as an effective analgesic technique in
children.6 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. Blocking the sciatic nerve in the
popliteal fossa is an excellent choice for foot and ankle
surgery.1 When used as a sole technique in outpatients,
popliteal fossa block provides excellent anesthesia and postoperative
analgesia, allows use of a calf tourniquet, and is devoid of disadvantages
of neuraxial blockade.7
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Indications & Contraindications
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The popliteal block is one of the most commonly used regional
anesthesia techniques in regional anesthesia practice.
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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The sciatic nerve is a nerve bundle
consisting of two separate nerve trunks, the tibial and common peroneal
nerves. A common epineural sheath envelops these two nerves at their outset
in the pelvis.11 As the sciatic nerve descends toward the
knee, the two components eventually diverge in the popliteal fossa, giving
rise to tibial and common peroneal nerves (Figure 38–1). This
division of the sciatic nerve occurs usually between 50 and 120 mm proximal
to the popliteal fossa crease.12,...