Efficacy of systemic lidocaine versus ultrasound-guided adductor canal block for patients undergoing total knee arthroplasty: a randomized, double-blinded, non-inferiority study

Background Total knee arthroplasty (TKA) is associated with significant postoperative pain; therefore, adductor canal block is commonly used as part of multimodal analgesia. Intravenous lidocaine may provide a practical alternative when regional anesthesia is not feasible. This study compared intravenous lidocaine with ultrasound-guided adductor canal block for postoperative opioid consumption, pain scores, and quality of recovery within the first 24 hours after outpatient TKA. Methods In this non-inferiority trial, 120 patients undergoing TKA were randomized 1:1 to receive either a single injection adductor canal block with saline infusion or intravenous lidocaine infusion with sham block. The primary outcome was opioid consumption 24 hours after surgery, with a prespecified non-inferiority margin of 30 mg oral morphine equivalents (OME). Secondary outcomes included pain scores, time to first analgesic request, quality of recovery, and patient satisfaction. Results Median OME consumption was 57.5 mg (IQR 37.5–77.5) in the lidocaine infusion group and 52.5 mg (IQR 30–77.5) in the adductor canal block group, with a median difference of 5.0 mg (95% CI −11.2 to 16.2), below the prespecified non-inferiority margin. In post-anesthesia care unit (PACU), median opioid consumption and pain scores at discharge were lower in the adductor canal block group than in the lidocaine group, with a median difference of 10 mg OME (95% CI 1.0 to 11.2; p=0.02) and two points (95% CI 0.33 to 4; p=0.02), respectively. There were no study-related adverse events. Time to first analgesic request, quality of recovery, and patient satisfaction were similar between groups. Conclusions Continuous intravenous lidocaine was non-inferior to adductor canal block for postoperative analgesia at 24 hours after TKA. Although adductor canal block provided better immediate PACU analgesia, both strategies were comparable thereafter, supporting lidocaine as a useful option when regional anesthesia is not feasible.