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.
Patients scheduled for elective unilateral surgery below the knee (e.g., internal fixation for ankle, metatarsal, or calcaneal fractures; hallux valgus correction; flatfoot reconstruction).
American Society of Anesthesiologists (ASA) physical status class I or II.
Aged 18 to 65 years.
Ability to understand the study procedure and provide written informed consent.
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.
Parallel
Ultrasound-guided lateral mid-femoral sciatic nerve block
Procedure/SurgeryUltrasound-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
Ultrasound-guided popliteal sciatic nerve block
Procedure/SurgeryUltrasound-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).
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.
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.
Sensory Block Onset Time
Time interval from the end of local anesthetic injection to the achievement of complete sensory blockade (Grade III).
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).
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).
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