Comparing Classical Approach and Crosswise Approach to Popliteal Sciatic Nerve Block

Classical Popliteal Sciatic Block Versus Crosswise Approach for Popliteal Sciatic (CAPS) Block in Below Knee Surgery:A Randomised Control Trial

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.

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)