A Randomized Non-Inferiority Trial of Adductor Canal Block for Analgesia After Total Knee Arthroplasty: Single Injection Versus Catheter Technique

Background Adductor canal blocks (ACBs) provide effective analgesia following total knee arthroplasty. We hypothesized that ACB single injection plus intravenous (IV) dexamethasone (Dex) shows non-inferiority to catheter, while ACB single injection does not. Methods One hundred eighty patients were randomized and 177 analyzed from among 1 of 3 ACB interventions: (1) 0.5% ropivacaine 20 mL; (2) 0.5% ropivacaine 20 mL plus IV Dex 8 mg; (3) 0.5% ropivacaine 20 mL followed by continuous infusion of 0.2% ropivacaine at 5 mL/h for 48 hours. The primary endpoint was cumulative opioid consumption at 24 hours in oral morphine equivalents, with a non-inferiority limit of 30 mg. Secondary endpoints included opioid consumption at 12 and 48 hours, rest pain scores, quality of recovery survey, length of stay, and anti-emetic usage. Results For 24-hour opioid consumption, single injection ACB with and without IV Dex had a mean difference of −24.2 mg (confidence interval [CI] 0.5 to −48.9, P < .001) and −21 mg (CI 3.2 to −45.1, P < .001) relative to catheter, demonstrating non-inferiority. Non-inferiority was also shown at 12 hours by Dex and single injection over catheter with mean difference of −20.4 mg (CI −6.8 to −33.9, P < .001) and −15.1 mg (CI −2.1 to −28.2, P < .001), respectively. No intergroup difference was found for 48-hour opioid consumption. No differences in other secondary outcomes were observed across the 3 groups. Conclusion Single injection ACB, with and without IV Dex, is non-inferior to ACB catheters in 24-hour opioid consumption, and may be attractive options for early-discharge, fast-track total knee arthroplasty.