Total knee arthroplasty (TKA) is among the most frequently performed surgical procedures for degenerative joint diseases, including advanced knee osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis. More than 700,000 TKA procedures are performed annually in the United States alone since 2012, with projections estimating a 143% increase by 2050. A significant proportion of patients experience moderate to severe postoperative pain following the procedure, adversely affecting early mobilization, adherence to rehabilitation programs, and ultimately functional recovery .
Femoral nerve block (FNB) was historically the cornerstone of TKA analgesia; however, concerns about quadriceps weakness and associated fall risk led to its replacement by more motor-sparing alternatives . Adductor canal block (ACB) has since become the standard approach, providing analgesia equivalent to FNB while significantly preserving quadriceps strength . Nevertheless, ACB does not adequately cover the posterior capsule and popliteal plexus terminals; consequently, 60-80% of TKA patients report significant posterior knee pain that cannot be sufficiently managed by ACB alone .
To address this limitation, several posterior knee analgesia techniques have been described. The IPACK (Interspace between Popliteal Artery and Capsule of the Knee) block targets genicular nerve branches and popliteal plexus terminals by injecting local anesthetic between the popliteal artery and the posterior knee capsule, largely sparing the main motor trunks and providing selective posterior analgesia . The adductor magnus muscle plane (AMM) block is a relatively novel interfascial plane block technique applicable in the supine position simultaneously with ACB. By injecting local anesthetic into the fascial plane along the posterior surface of the adductor magnus muscle, the AMM block aims to spread to the popliteal plexus and posterior capsular branches, potentially mimicking a sciatic nerve block effect . A key advantage of the AMM block is its applicability without patient repositioning during the same session as ACB.
The primary objective of this prospective randomized trial was to compare the effects of IPACK and AMM blocks-both added to ACB-on postoperative opioid consumption in patients undergoing TKA. Secondary objectives included evaluating the impact of each technique on postoperative pain scores, mobilization time, functional recovery, and motor function