Comparing Classical Approach and Crosswise Approach to Popliteal Sciatic Nerve Block

National University of Malaysia

Status: Completed

Conditions: Popliteal Sciatic Nerve Block

Treatments: Procedure: Popliteal Plexus Block with 20 ml

Study type: Interventional

Funder types: Other

Identifiers

NCT07134608

JEPUKM-JEP-2023-973

Details and patient eligibility

About

Sensory and motor innervation below the knee is provided mainly by the popliteal-sciatic nerve except for a variable area of the medial leg supplied by the saphenous nerve. Regional anaesthesia and analgesia for below knee surgery are frequently provided by blocking the popliteal sciatic nerve in the popliteal fossa. Popliteal sciatic block was first introduced around the 1970s and has emerged as a popular technique for below knee surgery despite other types of lower limb peripheral nerve block. This is contributed because popliteal fossa offers a superficial and accessible location for nerve blockade. This anatomical feature simplifies the procedure and may reduce the risk of complications such as vascular puncture or nerve injury.

Analgesia provided by the popliteal sciatic block lasts significantly longer than with ankle blocks. One of the reasons is administration of local anaesthetic agent at the popliteal fossa allows it to bathe the sciatic nerve before it bifurcates into the tibial and common peroneal nerves, leading to a more extensive and prolonged nerve blockade. Besides the sciatic nerve at the popliteal level is encased in a common epineural sheath, which can facilitate the spread of the anaesthetic and prolong its effect. The popliteal sciatic block can be performed as a single-shot technique or as a continuous infusion via a catheter The success rate of popliteal sciatic block is dependent on several variables, including the operator's skill, patient considerations, and surgical variables.

This study comparing between 2 approaches of popliteal sciatic nerve ie: classical approach and relatively new approach that is crosswise approach of popliteal sciatic nerve (CAPS) block.

Enrollment: 80 patients

Sex: All

Ages: 18+ years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• planned for either elective or non-elective unilateral below-knee surgery at HUKM
• patients aged 18 years and older and classified as physical status I, II, or III as dictated by the American Society of Anaesthesiologists (ASA)

Exclusion criteria

• included pregnant patients, those with a body mass index (BMI) ≥40 kg/m², contraindicated to peripheral nerve block (such as existing nerve injury to the limb intended for surgery), patient refusal, severe coagulopathy, local anaesthetic (LA) allergy, active infection at the intended block site, patients unable to provide a pain score using a verbal numerical rating scale (VNRS)

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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80 participants in 2 patient groups

Classical Popliteal Sciatic Nerve Block

Active Comparator group

Description:

Patients turned to the right or left lateral decubitus position, depending on which lower limb was planned for operation (i.e., right lateral decubitus if the operation was on the left lower limb and vice-versa). A pillow was placed between the lower limbs to facilitate block access and patient comfort. The classical popliteal sciatic block was done using a ultrasound machine with a high-frequency linear or low-frequency curvilinear probe placed 5-6 cm cranial to the popliteal fossa crease while identifying the bifurcation of the sciatic nerve. Skin infiltration with 5 ml of lignocaine 2% was performed using a 23G,followed by in-plane introduction of an 80 mm 22G block needle, aiming to penetrate the sciatic nerve sheath at the level of bifurcation, with placement confirmed using a nerve stimulator. After confirming negative aspiration for blood, 20 ml of Ropivacaine 0.5% was injected, and the spread of LA within the sheath was confirmed by ultrasound.

Treatment:

Procedure: Popliteal Plexus Block with 20 ml

Crosswise Approach to Popliteal Sciatic Nerve (CAPS block)

Active Comparator group

Description:

Patients in remained in the supine position. The CAPS block was performed using a similar Sonosite SII® ultrasound machine with a high-frequency linear or low-frequency curvilinear probe placed lateral to the thigh, 5-6 cm cranial to the popliteal fossa crease, while identifying the bifurcation of the sciatic nerve into the tibial and common peroneal nerves. Thereafter, the block proceeded similarly to patients in Group A, with 5 ml of lignocaine 2% for skin infiltration, in-plane introduction of the block needle aiming to penetrate the sciatic nerve sheath at the level of bifurcation and placement confirmed with a nerve stimulator, followed by injection of 20 ml of Ropivacaine 0.5% after confirming negative aspiration for blood. The spread of LA within the sheath was confirmed by ultrasound.

Treatment:

Procedure: Popliteal Plexus Block with 20 ml