Infiltration between the popliteal artery and the capsule of the knee (IPACK) vs. selective tibial nerve block for analgesia after anterior cruciate ligament reconstruction: a randomised controlled trial

Introduction: Infiltration between the popliteal artery and the capsule of the knee (IPACK) and the selective tibial nerve block both provide analgesia for the posterior aspect of the knee after anterior cruciate ligament reconstruction. This randomised controlled triple-blinded trial tested the hypothesis that IPACK provides superior analgesia to a selective tibial nerve block after anterior cruciate ligament reconstruction. Methods: Eighty patients having anterior cruciate ligament reconstruction under general anaesthesia with a femoral triangle block were allocated randomly to receive either IPACK with 20 ml ropivacaine 0.2% or a selective tibial nerve block with 5 ml ropivacaine 0.75%. Postoperative analgesia included paracetamol, ibuprofen and intravenous morphine patient-controlled analgesia. Primary outcome was cumulative postoperative intravenous morphine consumption at 24 h. Secondary pain-related outcomes included pain scores at rest and on movement at 2 h, 24 h and 48 h. Early functional outcomes evaluated were range of motion; quadriceps strength; and walking distance measured at 24 h and 48 h. Late functional outcomes included concentric quadriceps strength and single-hop test, measured at 4 months and 8 months. Results: Median (IQR [range]) cumulative intravenous morphine consumption at 24 h postoperatively was similar between IPACK (12 (6–20 [0–54]) mg) and selective tibial nerve block (16 (10–30 [0–66]) mg, p = 0.073). No significant differences between groups were seen in the secondary pain or functional outcomes. No complications were reported. Discussion: The IPACK and selective tibial nerve block provide comparable postoperative analgesia after anterior cruciate ligament reconstruction under general anaesthesia with a femoral triangle block, with similar impact on functional outcomes.