Does Interneural Local Anesthetic Spread at the Site of Sciatic Nerve Bifurcation Shorten Block Onset Time?

Does Interneural Local Anesthetic Spread at the Site of Sciatic Nerve Bifurcation Shorten Block Onset Time?

Following foot and ankle surgery, ultrasound-guided sciatic nerve block (SNB) at the popliteal fossa decreases post-operative pain and opioid consumption. At the popliteal fossa, the sciatic nerve bifurcates to form the Common Peroneal Nerve (CPN) and Tibial Nerve (TN). Studies have shown that when both branches are blocked separately distal to the bifurcation site, block onset time is reduced by 30%. Through clinical observation, the investigators found that onset time is further shortened when ultrasound-guided SNB is performed at the site of bifurcation. This is because the local anesthetic spreads interneurally. The purpose of this study is to compare the block onset time of an ultrasound-guided sciatic nerve block at the site of nerve bifurcation with the blockade of each terminal nerve separately (TN and CPN) distal to sciatic nerve bifurcation.

Inclusion Criteria:

• ASA physical status I-III
• 18-85 years of age, inclusive
• 50-120 kg, inclusive
• 150 cm of height or greater

Exclusion Criteria:

• Contraindications to sciatic nerve block (e.g., allergy to local anesthetics, coagulopathy, malignancy or infection in the popliteal area)
• Significant peripheral neuropathy or neurological disorder affecting the lower extremity
• Pregnancy
• History of alcohol or drug dependency/abuse
• History of significant psychiatric conditions that may affect patient assessment