Efficacy of Modified Periarticular Infiltration Compared with Conventional Periarticular Infiltration in Controlling Pain After Total Knee Arthroplasty: A Randomized Controlled Non-Inferiority Trial

Purpose: Patients with end-stage knee osteoarthritis typically undergo total knee arthroplasty (TKA), a surgical procedure that has long been considered a cost-effective treatment. However, moderate to severe postoperative pain is a common problem following TKA. Therefore, in this study, we aimed to compare the effects of postoperative pain management using conventional periarticular infiltration (conventional periarticular infiltration [PA]) versus modified periarticular infiltration (modified PA). Methods: This study was designed as a randomized controlled non-inferiority clinical trial conducted from April 2024 to April 2025. A total of 58 patients undergoing primary unilateral TKA were enrolled and randomly assigned to receive either modified PA or conventional PA. The primary outcome was postoperative pain within the first 24 h after surgery, measured using the visual analog scale. Secondary outcomes included time to first morphine hydrochloride rescue, total morphine consumption during the first 24 postoperative hours, and length of hospital stay (LOS). Results: Modified PA was non-inferior to conventional PA for postoperative pain control at rest and during movement within 24 h after TKA. Time to first morphine rescue, 24 h morphine consumption, and LOS did not differ significantly between the groups. All mean differences and corresponding 95% confidence intervals remained within the predefined non-inferiority margin of 0.5. Conclusions: Modified PA and conventional PA provided comparable pain relief during the first 24 h after TKA and showed similar times to first morphine rescue. Morphine consumption and LOS were similar between the groups. These findings may inform the selection of intraoperative analgesic infiltration techniques.