Determination of the Optimal Volume of Liposomal Bupivacaine in Adductor Canal Block for Knee Joint Surgery

"Patient Positioning: Supine with the surgical limb slightly flexed and externally rotated.~Operator Setup: The operator stands on the surgical side, with the ultrasound machine positioned contralaterally. The anterior thigh is sterilized and draped.~Ultrasound Technique: A high-frequency (5-12 MHz) linear ultrasound probe (Sonosite M-Turbo), protected by a 3M Tegaderm dressing, is placed perpendicular to the skin at the midpoint between the femoral trochanter and the superior patellar margin. The probe is maneuvered to visualize the adductor canal structures.~Needle Insertion: After local anesthesia at the insertion site, a 22G 80 mm needle is advanced using an in-plane technique until the tip reaches the triangular hypoechoic area lateral to the femoral artery. Following negative aspiration for blood, 1.33% liposomal bupivacaine is injected around the target site."