iPACK Block vs. Periarticular Infiltration for TKA Pain Control

Total knee arthroplasty (TKA) is a highly successful procedure for end-stage knee osteoarthritis but is associated with significant postoperative pain. Effective pain management is crucial for facilitating early rehabilitation and improving patient comfort. Modern pain management relies on multimodal, opioid-sparing protocols that often include motor-sparing regional anesthesia techniques like the femoral triangle block (FTB). While FTB provides excellent analgesia for the anterior part of the knee, pain originating from the posterior knee capsule remains a significant challenge. This posterior pain is commonly managed either by the surgeon through a diffuse periarticular infiltration (PAI) of a local anesthetic cocktail or by the anesthesiologist through a targeted, ultrasound-guided block of the posterior capsule known as the iPACK block. It is currently unclear whether a fully anesthesiologist-driven, neuroanatomically targeted approach (FTB + iPACK) offers superior outcomes compared to a hybrid approach involving both the anesthesiologist and the surgeon (FTB + PAI). This prospective, randomized, double-blind controlled trial is designed to compare these two advanced analgesic combinations. All patients will receive a standardized spinal anesthetic (3 mL of 0.5% heavy bupivacaine). The study will evaluate which method provides better pain control, measured primarily by Numeric Rating Scale (NRS) pain scores at 24 hours, and secondarily by total rescue analgesic (tramadol) consumption, functional recovery (Timed Up and Go test and Straight Leg Raise test), and knee range of motion. Sample size will be determined based on an internal pilot study. An initial 30 patients (15 per group) will be enrolled. The mean and standard deviation of the primary outcome (NRS pain score with movement at 24 hours) from this pilot cohort will be used to calculate the final sample size required to detect a clinically significant difference (e.g., 1 point on the NRS) with 80% power and an alpha of 0.05. The final enrollment target is estimated to be approximately 100 patients (50 per group) to account for potential dropouts.