A randomized clinical trial of addition of IPACK block or selective tibial nerve block to adductor canal block for postoperative pain management after total knee arthroplasty

Background & Objective: Postoperative pain after total knee arthroplasty (TKA) is a significant factor influencing the surgical outcome. Adductor canal block (ACB) has no analgesic effect on the posterior knee capsule, which is innervated by the terminal branches of the tibial nerve and the posterior branch of the obturator nerve. We compared ACB plus IPACK block (infiltration of the interspace between the popliteal artery and the posterior capsule of the knee) versus ACB with selective tibial nerve block (TNB) for pain management after TKA. Methodology: We enrolled 70 patients, aged 40-80 y, body mass index of 18.5-35 kg/m2, scheduled for TKA in the study. Patients were randomly allocated to one of the two equal groups; Group 1 to receive ACB with IPACK block and Group 2 to receive ACB with TNB. Duration of sensory block, motor block, time to first rescue analgesic request, time to ambulation, and hospital length were noted in both groups. The 0-10 numeric rating scale (NRS) was used to measure the pain intensity in the patients. Results: Duration of sensory block, motor block, time to first rescue analgesic request, time to ambulation, and hospital length were significantly increased in Group 2 than in Group 1 (P < 0.001). The numeric rating scale was significantly lower in Group 2 at 8 h only but was comparable in other measurements. Range of motion and the strength of quadriceps were comparable between both groups at 24, 48, and 72 h postoperatively. Conclusions: Adductor canal block with IPACK preserved motor function better and reduced the time to ambulation and hospital stay compared to tibial nerve block with adductor canal block. However, adductor canal block with selective tibial nerve block prolongs sensory block, the time to first analgesia request, and reduces postoperative opioid consumption at first 24 h. Both methods had a comparable effect on quadriceps strength.