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.
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.
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.
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.
Therapeutic level I.

An ultrasound-guided anesthetic technique targeting the interspace between the popliteal artery and capsule of the posterior knee (iPACK) can provide posterior knee analgesia with preserved motor function after total knee arthroplasty (TKA). This study compared the peroneal nerve motor-sparing effects of iPACK block and tibial nerve block (TNB) when combined with local infiltration analgesia (LIA) and continuous adductor canal block (CACB).
In this study, 105 patients scheduled for elective TKA were randomized to receive proximal iPACK block (iPACK1), distal iPACK block (iPACK2), or TNB, along with spinal anesthesia, modified LIA, and CACB. The primary outcome was the incidence of common peroneal nerve (CPN) motor blockade. Secondary outcomes included CPN sensory function, tibial sensorimotor function, posterior knee pain, pain score, intravenous morphine requirement, timed up-and-go test, quadriceps muscle strength, range of motion, length of hospital stay, patient satisfaction, and adverse events.
The incidence of CPN motor blockade was significantly higher in the TNB group than in the iPACK1 (p=0.001) and iPACK2 (p=0.001) groups, but was not significant between the iPACK1 and iPACK2 groups (p=0.76). Tibial nerve motor function was more preserved in the iPACK1 and iPACK2 groups than in the TNB group (p<0.001 and p<0.001, respectively). Complete CPN and tibial sensorimotor blockade were not observed in the iPACK2 group. Posterior knee pain score was significantly higher in the iPACK1 group than in other groups during the 24-hour postoperative period (p=0.001).
Compared with TNB, iPACK1 and iPACK2 preserved CPN and tibial nerve motor function to a greater extent. However, iPACK2 did not demonstrate complete CPN and tibial nerve motor blockade while maintaining effective posterior knee pain relief.
TCTR20180206002.