Feasibility and Safety of Sciatic Nerve Paraneural Sheath Block Using a Mid-Femoral Lateral Approach (iSNB-LF)

Feasibility and Safety of Intraneural Sciatic Nerve Block Via Lateral Mid-femoral Approach: A Clinical Study

This study is designed as a randomized controlled trial aiming to evaluate the feasibility and safety of ultrasound-guided mid-femoral lateral approach sciatic nerve paraneural sheath block, in order to provide a new sciatic nerve block approach for clinical practice that offers greater patient comfort and higher precision, thereby facilitating its use for specific patient populations and less experienced operators.

Study Overview

• Status: Not yet recruiting
• Conditions: Adverse Effect; Safety and Effectiveness; Feasibility Study
• Intervention / Treatment: Procedure: Ultrasound-guided lateral mid-femoral sciatic nerve block; Procedure: Ultrasound-guided popliteal sciatic nerve block

Detailed Description

In clinical practice, the popliteal approach to sciatic nerve paraneural sheath block is the most commonly used. Studies have found that compared with extraneural injection, ultrasound-guided sciatic nerve paraneural sheath block via the popliteal approach has a faster onset and provides longer postoperative sensory and motor blockade. Paraneural sheath block aims to achieve efficient, rapid, and precise nerve blockade using a low volume of local anesthetic. However, the popliteal approach requires knee flexion for performance, necessitating the patient to be in a prone or lateral decubitus position. For patients unable to flex the knee or those with positioning difficulties due to conditions such as lower limb fractures, this method is less applicable. For the above reasons, the popliteal sciatic nerve block has certain limitations.

The mid-femoral lateral approach demonstrates unique advantages: First, the patient can maintain a supine position throughout the procedure, significantly enhancing comfort and compliance. Second, the sciatic nerve is relatively superficial at this level, offering good ultrasonographic visualization and being distant from major blood vessels and nerves. This makes it applicable even in obese patients with thick subcutaneous fat and suboptimal ultrasound images, theoretically enhancing procedural safety. Therefore, it is considered an effective solution for patients with positioning restrictions, such as those with lower limb fractures and severe pain, holding high potential for clinical promotion and research significance.

Although the anatomical feasibility of this approach has been preliminarily confirmed, its practical feasibility and safety require validation through clinical studies. In particular, whether a successful "paraneural sheath block" can be consistently achieved at the mid-femoral lateral level, similar to the classic popliteal approach, remains to be explored. While some literature suggests its theoretical feasibility, there is a lack of prospective, systematic clinical research evidence to support its practical application feasibility (e.g., block efficacy, procedural difficulty, success rate) and safety (e.g., complication rates, incidence of nerve injury).

This study is designed as a randomized controlled trial aiming to evaluate the feasibility and safety of ultrasound-guided mid-femoral lateral approach sciatic nerve paraneural sheath block. The goal is to provide a new sciatic nerve block option for clinical practice that offers greater patient comfort and more precise blockade, facilitating its use for specific patient populations and less experienced operators.

• Study Type: Interventional
• Enrollment (Estimated): 200
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Gang Ma, MD，PhD; Phone Number: 13709519220; Email: magang2671@173.com
• Study Contact Backup: Name: Yan Ren, MD; Phone Number: 18152372612; Email: 3467592762@qq.com

Study Locations

• China
  • Ningxia
    • Yinchuan, Ningxia, China, 750004
      • General Hospital of Ningxia Medical University
      • Contact: Yan Ren, MD; Phone Number: 18152372612; Email: 3467592762@qq.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Patients scheduled for elective unilateral surgery below the knee (e.g., internal fixation for ankle, metatarsal, or calcaneal fractures; hallux valgus correction; flatfoot reconstruction).
2. American Society of Anesthesiologists (ASA) physical status class I or II.
3. Aged 18 to 65 years.
4. Ability to understand the study procedure and provide written informed consent.

Exclusion Criteria:

1. Contraindications to peripheral nerve block:

   • Known allergy or history of toxicity to local anesthetics.
   • Pre-existing neuropathy in the operative limb.
   • Severe coagulopathy.
   • Infection at the intended needle puncture site.
   • Systemic infection.
2. Requirement for simultaneous surgery at a site other than the unilateral lower limb below the knee.
3. Previous surgery or significant scarring in the area of the planned needle insertion for the sciatic nerve block.
4. Body mass index (BMI) > 35 kg/m².
5. Patients receiving chronic pain therapy or with a history of opioid abuse.
6. Inability to communicate or cooperate with the study assessments (e.g., due to cognitive impairment, language barrier, or psychiatric disorder).
7. Pregnancy or lactation.

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
Experimental: Lateral Mid-femoral Approach Sciatic Nerve Block; Ultrasound-guided sciatic nerve subparaneural sheath block via the lateral mid-femoral approach. Under combined ultrasound and nerve stimulator guidance, a single injection of 20 mL of 0.5% ropivacaine hydrochloride will be administered into the paraneural sheath at the mid-femoral level.	Procedure: Ultrasound-guided lateral mid-femoral sciatic nerve block; Ultrasound-guided sciatic nerve subparaneural sheath block via the lateral mid-femoral approach. Under combined ultrasound and nerve stimulator guidance, a single injection of 20 mL of 0.5% ropivacaine hydrochloride will be administered into the paraneural sheath at the mid-femoral level
Active Comparator: Popliteal Approach Sciatic Nerve Block; Ultrasound-guided sciatic nerve subparaneural sheath block via the conventional popliteal approach. Under combined ultrasound and nerve stimulator guidance, a single injection of 20 mL of 0.5% ropivacaine hydrochloride will be administered into the paraneural sheath at the popliteal fossa (prior to nerve bifurcation).	Procedure: Ultrasound-guided popliteal sciatic nerve block; Ultrasound-guided sciatic nerve subparaneural sheath block via the conventional popliteal approach. Under combined ultrasound and nerve stimulator guidance, a single injection of 20 mL of 0.5% ropivacaine hydrochloride will be administered into the paraneural sheath at the popliteal fossa (prior to nerve bifurcation).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of complete sensory blockade in the sciatic nerve distribution at 30 minutes after block completion	The proportion of patients achieving complete sensory blockade (Grade III: numbness, no sensation to pinprick) in the tibial and common peroneal nerve distributions at 30 minutes following the administration of the local anesthetic. Sensory blockade will be assessed using von Frey filaments and compared to the contralateral limb.	At 30 minutes after completion of the local anesthetic injection.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Block Success Rate	Proportion of patients achieving both complete sensory blockade (Grade III) and complete motor blockade (Grade III) in the sciatic nerve distribution at 30 minutes after local anesthetic injection.	At 30 minutes after block completion.
Sensory Block Onset Time	Time interval from the end of local anesthetic injection to the achievement of complete sensory blockade (Grade III).	From the end of injection until complete sensory block is achieved (assessed every 30 seconds), up to 30 minutes.
Duration of Sensory Block	Time interval from the onset of complete sensory blockade to the first complaint of pain in the surgical area (NRS > 0).	From block onset until first pain complaint, assessed up to 48 hours postoperatively.
Motor Block Onset Time	Time interval from the end of local anesthetic injection to the achievement of complete motor blockade (Grade III: inability to move the ankle).	From the end of injection until complete motor block is achieved (assessed every 30 seconds), up to 30 minutes.
Duration of Motor Block	Time interval from the onset of complete motor blockade to the recovery of normal ankle flexion and extension.	From block onset until full motor recovery, assessed up to 48 hours postoperatively.
Time to First Request for Rescue Analgesia	Time interval from the end of surgery to the patient's first activation of the patient-controlled intravenous analgesia (PCIA) pump or request for supplemental analgesia.	From end of surgery until first rescue request, assessed up to 24 hours postoperatively.
Total Consumption of Rescue Analgesics within 24 Hours	Total dose of rescue analgesics (e.g., parecoxib, ketorolac, morphine) administered within the first 24 postoperative hours.	Within 24 hours after surgery.
Postoperative Pain Intensity (NRS Scores)	Pain intensity assessed using the Numerical Rating Scale (NRS, 0-10) at rest and during movement at 4, 8, and 24 hours postoperatively.	At 4, 8, and 24 hours after surgery.
Incidence of Rebound Pain	Proportion of patients experiencing rebound pain, defined as an NRS score >7 within 48 hours after block resolution, not relieved by multiple PCIA boluses within 30 minutes.	Within 48 hours after block resolution.
Procedure-Related Times	Ultrasound Scanning Time: Time from probe placement to clear identification of the target nerve.; Total Needle Manipulation Time: Time from needle insertion to completion of drug injection.	During the block procedure.
Number of Needle Redirections	Total number of times the nerve stimulation needle is adjusted or redirected to achieve the final position.	During the block procedure.
Incidence of Complications	Proportion of patients experiencing block-related complications, including local anesthetic systemic toxicity, nerve injury (persistent neuropathy), hematoma, or infection.	From block procedure up to 1 week postoperatively.
Patient Satisfaction Score	Patient-reported satisfaction with the overall anesthesia and analgesia experience, assessed using a 5-point Likert scale (0=very dissatisfied, 5=very satisfied).	At 24 hours postoperatively.

Collaborators and Investigators

• Sponsor: General Hospital of Ningxia Medical University

Study record dates

Study Major Dates

• Study Start (Estimated): January 1, 2026
• Primary Completion (Estimated): September 1, 2026
• Study Completion (Estimated): October 1, 2026

Study Registration Dates

• First Submitted: January 8, 2026
• First Submitted That Met QC Criteria: January 16, 2026
• First Posted (Actual): January 26, 2026

Study Record Updates

• Last Update Posted (Actual): January 26, 2026
• Last Update Submitted That Met QC Criteria: January 16, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: Safety; Feasibility; Ultrasound-guided; Sciatic Nerve Block; Subparaneural Block; Lateral Mid-femoral Approach; Popliteal Approach
• Other Study ID Numbers: Yan Ren-2026-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No