BackgroundA combination of motor-sparing analgesia with local infiltration analgesia (LIA) and continuous adductor canal block (CACB) may improve postoperative pain and functional recovery for total knee arthroplasty (TKA). We hypothesized that the addition of a novel technique for posterior knee block, known as the infiltration between the popliteal artery and capsule of the knee (iPACK) block, to LIA with CACB would reduce opioid requirements.MethodsIn this double-blinded randomized controlled trial, 72 patients were assigned to receive either LIA with CACB (LIA+CACB group) or iPACK block with LIA and CACB (iPACK+LIA+CACB group). The primary outcome was cumulative postoperative intravenous morphine consumption within 24 hours. The secondary outcomes included numerical rating scale pain scores, incidence of posterior knee pain, performance test results, patient satisfaction, length of stay, and adverse events.ResultsMorphine consumption within 24 hours postoperatively showed no significant intergroup difference (LIA+CACB; 1.31±1.85 mg vs iPACK+LIA+CACB; 0.61±1.25 mg, p=0.08). There were no clinically significant differences in the overall pain scores between the groups. The lower Timed Up and Go test scores on postoperative days 1 and 2, along with a shorter duration of hospitalization, were found in the iPACK+LIA+CACB group (p<0.05).ConclusionThe addition of an iPACK block to the LIA and CACB does not reduce the postoperative opioid consumption nor improve analgesia. However, it may improve immediate functional performance and reduce the length of hospitalization after TKA.Trial registration numberTCTR20180702001.

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Background and objectiveAn 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).MethodsIn 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.ResultsThe 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).ConclusionsCompared 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.Trial registration numberTCTR20180206002.