Ultrasound Guided Popliteal Fossa Block. Does Blockade Distal to Sciatic Nerve Bifurcation Speed Onset Time? A Prospective, Randomized Trial

Sciatic nerve block is used routinely in ankle and foot surgery. It is applied often by a posterior approach at the popliteal fossa, near where the nerve divides into the common peroneal and tibial nerves. Due to the size of the sciatic nerve, the largest in the body, infiltration of anesthetic and onset of anesthesia can take a significant amount of time. This study hypothesizes that selectively blocking both the common peroneal and the tibial nerves distal to the bifurcation may result in a faster block onset than blockade of the sciatic nerve proximal to its bifurcation.

Study Overview

• Status: Completed
• Conditions: Ankle/Foot Surgery
• Intervention / Treatment: Procedure: Sciatic nerve blockade for ankle/foot surgery

Detailed Description

Sciatic nerve block (SNB) has been shown to reduce postoperative pain and opioid requirements, as well as improve patient satisfaction after outpatient foot and ankle surgery. The sciatic nerve divides into two terminal branches (the common peroneal and tibial nerves) in the popliteal fossa. Through these two branches it innervates the entire leg, ankle and foot except for the skin over the anterior-medial aspect of the leg, which is supplied by the saphenous nerve, a branch of the femoral nerve.

Many approaches have been described to sciatic nerve blockade. High in the thigh or buttock are the classical posterior approach, the supine approach, and the anterior approach. In the popliteal fossa, a posterior, a lateral and a medial approach have been described. The popliteal fossa approaches are most commonly used to provide regional anesthesia and/or analgesia for major foot and ankle surgery.

Traditional nerve localization techniques include seeking paresthesiae on needle to nerve contact, or alternatively seeking a muscle response to electrical nerve stimulation using a blunt insulated needle and a peripheral nerve stimulator. However, block results with traditional nerve localization techniques are highly variable, often requiring high local anesthetic doses, and a prolonged onset time. When a distal approach in the popliteal fossa is used (5-7 cm above the knee crease) with a nerve stimulator technique, a double motor response (both tibial and peroneal components) may be required to achieve consistent success.

Recently, ultrasound guided techniques for SNB at the popliteal fossa have been described. Ultrasound guidance offers the unique advantages of real time anatomic assessment of the sciatic nerve itself, its site of bifurcation, and its relationship to surrounding muscles and the popliteal vessels. In a recent study we have shown that ultrasound guidance significantly improves the success rate of SNB at the popliteal fossa via a posterior approach.

Despite these advantages, a prolonged onset time for complete blockade of up to 30-60 minutes (depending on the choice and dose of local anesthetic) is common. This may be a limitation to the widespread use of popliteal sciatic nerve blockade in a peri-operative environment, where a faster block onset may be preferable. This delayed onset has been attributed to the large size of the sciatic nerve. Therefore logically it should be faster to induce a block by depositing the local anesthetic after the sciatic nerve divides where the connective tissues decrease and the nerves are superficial. No exact mathematical data is available looking into onset times for nerves with varying diameter, as no previous studies are done in this area.

• Study Type: Interventional
• Enrollment (Actual): 55
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5T 2S8
      • Toronto Western Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 85 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

1. ASA physical status I-III
2. 18-85 years of age, inclusive
3. 50-120 kg, inclusive
4. 150 cm of height or grater Scheduled for major elective foot or ankle surgery for which sciatic nerve block is indicated

Exclusion Criteria:

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 1; Local anesthetic will be injected above the division of the sciatic nerve.	Procedure: Sciatic nerve blockade for ankle/foot surgery; Injection of local anesthetic near the nerve to achieve anesthesia.
Experimental: 2; Local anesthetic will be injected below the division of the sciatic nerve, around the common peroneal and tibial nerves.	Procedure: Sciatic nerve blockade for ankle/foot surgery; Injection of local anesthetic near the nerve to achieve anesthesia.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Onset time of anesthesia.	every 5 minutes until start of surgery

Secondary Outcome Measures

Outcome Measure	Time Frame
Block procedure time, complications, location of the sciatic nerve bifurcation, postoperative pain, patient satisfaction with pain control	up to 2 days post-operative

Collaborators and Investigators

• Sponsor: University Health Network, Toronto

Study record dates

Study Major Dates

• Study Start: July 1, 2008
• Primary Completion (Actual): April 1, 2009
• Study Completion (Actual): April 1, 2009

Study Registration Dates

• First Submitted: December 4, 2008
• First Submitted That Met QC Criteria: December 4, 2008
• First Posted (Estimate): December 5, 2008

Study Record Updates

• Last Update Posted (Actual): November 27, 2017
• Last Update Submitted That Met QC Criteria: November 22, 2017
• Last Verified: July 1, 2009

More Information

Terms related to this study

• Keywords: nerve block; ultrasound-guided regional anesthesia; foot surgery; ankle surgery; popliteal fossa; sciatic nerve; common peroneal nerve; tibial nerve; onset time
• Other Study ID Numbers: 07-0495-B