Background: The combination of adductor canal block (ACB) and infiltration between the popliteal artery and the posterior capsule of the knee (iPACK) block may provide sufficient motor-sparing anterior and posterior knee analgesia after total knee arthroplasty. This study aimed to determine if ACB with iPACK block was noninferior to ACB with periarticular injection (PAI) when combined with postoperative multimodal analgesia regimen.

Methods: Seventy-six patients were randomized to receive either ACB + iPACK block and continuous ACB (CACB) (ACB + iPACK group) or PAI and CACB (ACB + PAI group). Noninferiority was concluded for the primary outcome if the adjusted mean between-group difference in pain on movement at 12 postoperative hours was within 1.3 points on a visual analog pain scale. Pain scores, morphine consumption, functional performance, and adverse events were the secondary outcome measures assessed for superiority.

Results: Adjusted mean differences, (ACB + iPACK) - (ACB + PAI), in anterior and posterior knee pain scores on movement at 12 postoperative hours were -0.66 (-1.86, 0.54) and -0.19 (-1.36, 0.99), respectively. The upper limit of 95% confident interval was lower than the prespecified noninferiority limit. The mean visual analog scale pain scores were low and no clinically significant differences between groups. However, morphine requirement at 48 postoperative hours was significantly higher (P < .05) and showed greater reduced quadriceps strength at 0 and 45 degrees on postoperative day 0 (P = .006 and .04, respectively) in the ACB + iPACK group.

Conclusions: ACB with iPACK block provides a noninferior analgesia compared with PAI when combined with CACB. However, patients who received ACB + iPACK block may require higher amounts of opioids and have worse immediate functional performance.