Timing of periarticular injection has no effect on postoperative pain and functional recovery in simultaneous bilateral total knee arthroplasty: a prospective randomized, double-blinded trial

Background: Given no consensus on optimal timeframe of periarticular multimodal drug injection (PMDI) in knee osteoarthritis patients undergoing total knee arthroplasty (TKA), this study was aimed to compare the postoperative pain and the functional recovery in patients who underwent simultaneous bilateral TKA (SBTKA) and received PMDI at the different intraoperative time points. Methods: This prospective, randomized, double-blinded controlled trial study included 48 patients who underwent SBTKA and received PMDI mixture, either before prosthetic implantation (late PMDI), or just after knee arthrotomy (early PMDI). Each subject's knees were randomly selected to different PMDI administration time points. The outcome parameters were postoperative pain assessed by using a visual analog scale (VAS), the maximal angle of knee flexion, and quadriceps function from day 1 to 6 weeks after surgery. Results: Late PMDI revealed slightly higher VAS at 6 and 12 h after the operation than early PMDI administration. Afterward, the VAS tended to be lower in the late than early PMDI administration until the end of the study, but without statistical significance. The time difference between early and late PMDI had no effect on postoperative VAS, while older age resulted in significantly less pain. No statistical differences between the two groups in all other outcome parameters were observed. Conclusions: Postoperative pain reduction and functional recovery of SBTKA with early and late PMDI administration were not significantly different. The time interval of PMDI between knees did not confound the comparison of postoperative pain and functional recovery in SBTKA.