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Analgesic efficacy of infiltration between the popliteal artery and capsule of the knee (iPACK) block added to local infiltration analgesia and continuous adductor canal block after total knee arthroplasty: a randomized clinical trial
  1. Chutikant Vichainarong1,
  2. Wirinaree Kampitak1,
  3. Aree Tanavalee2,
  4. Srihatach Ngarmukos2 and
  5. Nattaporn Songborassamee1
  1. 1 Anesthesiology, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society and Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
  2. 2 Orthopedics, King Chulalongkorn Memorial Hospital and Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
  1. Correspondence to Dr Wirinaree Kampitak, Anesthesiology, King Chulalongkorn Memorial Hospital, Bangkok 10330, Thailand; nutong127{at}


Background A 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.

Methods In 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.

Results Morphine 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).

Conclusion The 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 number TCTR20180702001.

  • continuous peripheral techniques
  • lower extremity
  • acute pain
  • pain measurement
  • ultrasound in pain medicine

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  • Contributors WK and CV: planning, conception, and design of the study, analyzed the data, interpretation of data, wrote the manuscript, and revised the manuscript. WK, AT and NS: planning and conducting the study, reporting, and acquisition of data, analyzed the data, and gave constructive criticism. AT and SN: performed all surgeries, postoperative management, interpretation of data, and gave constructive criticism.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval University of Missouri–Kansas City Office of Research Compliance (FWA 00005427). This single-center, prospective, double-blinded randomized controlled trial was approved by the Institutional Review Board of the Chulalongkorn University (Ref 327/61), and the trial was registered on the Thai Clinical Trials Registry before patient enrollment (principle investigator: WK; registration date: 2 July 2018; first enrollment date: 6 July 2018).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. ORCID iD: CV:; WK:; AT:; SN:; NS: