Anatomical Landmarks for Intraoperative Adductor Canal Block in Total Knee Arthroplasty: A Cadaveric Feasibility Assessment

BACKGROUND: Postoperative analgesia after knee arthroplasty forms a basis for an optimal range of motion after surgery. Femoral nerve blocks are established as a sensory nerve blockade but at the expense of quadriceps weakness delaying postoperative mobilization. The adductor canal block (ACB) similarly provides sensory blockade but preserves quadriceps function. If ACB is performed intraoperatively, it would reduce the time and cost needed for ACBs. This study aimed at investigating possible landmarks making it feasible to perform ACB intraoperatively. MATERIAL AND METHODS: Twenty-seven knees were used. The superior pole of the patella, medial epicondyle, and adductor tubercle was proposed as landmarks to perform the ACB through a medial parapatellar approach. A needle was directed toward the adductor tubercle until a tactile feedback was felt. Ten to 15 mL India ink were injected using this technique. The adductor canal was dissected to visualize the ink spread and determine whether the saphenous nerve and the nerve to vastus medialis were exposed to the ink. RESULTS: The anatomic landmarks were easily identified in all knees. The ACB resulted in the saphenous nerve and nerve to vastus medialis being bathed in ink consistently. A volumetric relationship was noted with the injectate. No injury to the neurovascular structures was observed. CONCLUSIONS: An accurate and safe technique with reliable anatomic landmarks was presented to perform an ACB. In addition, an increase in injected ink volume correlated to an increase in the spread of ink; thus, we postulate that 10 mL of local anesthetic may be sufficient for an adequate regional block.