RESUMEN
BACKGROUND: As an essential component of multimodal analgesia approaches after total knee arthroplasty (TKA), local infiltration analgesia (LIA) can be classified into peri-articular injection (PAI) and intra-articular injection (IAI) according to administration techniques. Currently, there is no definite answer to the optimal choice between the two techniques. Our study aims to investigate analgesic efficacy and safety of PAI versus IAI in patients receiving simultaneous bilateral TKA. METHODS: This randomized controlled trial was conducted from February 2017 and finished in July 2018. Sixty patients eligible for simultaneous bilateral total knee arthroplasty were randomly assigned to receive PAI on one side and IAI on another. Primary outcomes included numerical rating scale (NRS) pain score at rest or during activity at 3 h, 6 h, 12 h, 24 h, 48 h, and 72 h following surgery. Secondary outcomes contained active or passive range of motion (ROM) at 1, 2, and 3 days after surgery, time to perform straight leg raise, wound drainage, operation time, and wound complications. RESULTS: Patients experienced lower NRS pain scores of the knee receiving PAI compared with that with PAI during the first 48 h after surgery. The largest difference of NRS pain score at rest occurred at 48 h (PAI: 0.68, 95%CI[0.37, 0.98]; IAI: 2.63, 95%CI [2.16, 3.09]; P < 0.001); and the largest difference of NRS pain score during activity also took place at 48 h (PAI: 2.46, 95%CI [2.07, 2.85]; IAI: 3.90, 95%CI [3.27, 4.52]; P = 0.001). PAI group had better results of range of motion and time to perform straight leg raise when compared with IAI group. There were no differences in operation time, wound drainage, and wound complication. CONCLUSION: PAI had the superior performance of pain relief and improvement of range of motion to IAI. Therefore, the administration technique of peri-articular injection is recommended when performing local infiltration analgesia after total knee arthroplasty. TRIAL REGISTRATION: The trial was retrospectively registered in the Chinese Clinical Trial Registry as ChiCTR1800020420 on 29th December, 2018. LEVEL OF EVIDENCE: Therapeutic Level I.