Efficacy of adding an interspace block to the posterior knee for perioperative pain in total knee arthroplasty: a randomized controlled trial

Background and purpose: The interspace between the popliteal artery and the capsule of the posterior knee (IPACK) block is a novel anesthetic technique for total knee arthroplasty (TKA). Our objective was to compare the effect of IPACK and adductor canal block (ACB) and periarticular injection (PAI), relative to ACB and PAI only, from baseline to postoperative day 3, in patients undergoing unilateral primary TKA. Patients and methods: This was a single-center, double-blinded, randomized controlled trial. Adults over the age of 50 who were scheduled for unilateral primary TKA were enrolled. They were randomly assigned to ACB and PAI block (control group), or ACB, PAI, and IPACK block (IPACK group). The primary outcome was mean pain at rest during 24–48 hours post-operation using a numerical rating scale (0–10). We also investigated opioid use and ambulation pain. Results: 89 patients were evaluated, 45 from the control group and 44 from the IPACK group. Despite slightly higher mean pain score at rest in the control group, no statistically significant difference was found during 0–24 hours (0.13; 95% CI –0.19 to 0.46), 24–48 hours (0.42; CI –0.06 to 0.89), and 48–72 hours (0.35; CI 0.00 to 0.69) postoperatively as well as in maximum pain scores at rest. Neither pain during ambulation nor the number of opioids used differed between the trial groups at any given time point. Conclusion: The addition of the IPACK block to ACB and PAI did not reduce postoperative pain intensity or opioid usage. Therefore, IPACK block may not offer any benefit for pain management in patients undergoing unilateral primary TKA who are already receiving ACB and PAI.