A Comparative Study of Combined Adductor Canal and Interspace Between Popliteal Artery and Knee Capsule Versus Combined Adductor Canal and Genicular Nerve in Total Knee Arthroplasty

Spinal anesthesia will be chosen as the main anesthetic technique by injecting 3-3.5 ml of hyperbaric bupivacaine 0.5% by 24 G pencil-point needle at lumbar (L2-L3) or (L3-L4) space with 25 ug of fentanyl as adjuvant while patient is in setting position.

In both groups, the adductor canal block (ACB) will be performed with the patient in a supine position, the operative limb externally rotated, and the knee slightly flexed. A high-frequency ultrasound probe (10-15 MHz) will be positioned at the mid-thigh, at the midpoint of the line connecting the patella to the anterior superior iliac spine.

During the procedure, the following structures will be identified: the femoral artery, femoral vein, sartorius muscle, vastus medialis, and adductor longus. The hyperechoic appearance of the saphenous nerve will be visualized lateral to the femoral artery. Using an in-plane technique, 15 mL of 0.25% bupivacaine will be injected to achieve effective analgesia.

For (Group A) To perform the interspace between popliteal artery and knee capsule (IPACK) block, a curvilinear ultrasound probe (2-5 MHz) will first be positioned on the lower third of the medial thigh to identify the femoral vessels. The transducer will then be moved caudally into the popliteal fossa, allowing visualization of the femoral artery as it transitions into the popliteal artery. With the knee flexed at 90°, the needle will be advanced using an in-plane ultrasound-guided technique. The needle trajectory will be from medial to lateral, targeting the space between the popliteal vessels and the posterior capsule of the knee joint. Once the needle tip is positioned approximately 2 cm beyond the lateral border of the popliteal artery, an injection of 15 mL of 0.25% bupivacaine will be administered into this interspace.

For (Group B), The genicular nerve block (GNB) will target three peri-knee nerve branches: the superior medial genicular nerve (SMGN), inferior medial genicular nerve (IMGN), and superior lateral genicular nerve (SLGN). Each nerve will receive an injection of 5 mL of 0.25% bupivacaine.

For SMGN block the high frequency ultrasound probe will be placed laterally over the medial supracondylar area of the femur to identify the SMGN near the superior medial genicular artery, followed by injection adjacent to the artery. For the IMGN, the probe will be positioned over the medial condyle of the tibia to locate the inferior medial genicular artery near the neck of the tibia, again injecting adjacent to the artery. Finally, the SLGN will be targeted by placing the probe over the lateral condyle of the femur to find the superior lateral genicular artery, with the local anesthetic injected nearby.

The investigators will omit the inferolateral genicular nerve (ILGN) block to prevent any unwanted motor weakness or the potential for foot drop that may occur from inadvertently blocking branches of the common peroneal nerve. This decision aligns with the goal of optimizing analgesia while minimizing the risk of motor deficits, ensuring a safer and more effective postoperative recovery for patients undergoing knee arthroplasty.

In postoperative period all patients will receive the same adjuvant multimodal analgesia which will be 1000 mg of paracetamol with or without 30 mg ketorolac depending on comorbidities

Inclusion criteria

• Patients American Society of anesthesiologists' physical status (ASA) I to III.
• Aged 18 to 70 years.
• Both sexes.
• Patients scheduled for total knee arthroplasty.

Exclusion criteria

• Patient refusal
• ASA physical status IV or more.
• Patients with known allergy to any of the study drugs.
• Infection at the site of injection.
• Patients with neuromuscular disease.
• Presence of any coagulopathy.
• Patients with history of any psychiatric or cognitive disorder.
• patient with previous knee surgery.
• BMI more than 40 kg/m2.