Single-Injection Liposomal Bupivacaine Adductor Canal Block for Pain Control and Recovery After Total Knee Arthroplasty: A Randomized Controlled Double‑Blinded Study

Objective: The efficacy of the adductor canal block (ACB) in multimodal analgesia following total knee arthroplasty (TKA) remains controversial. This study investigates the effects of local anesthetics single-injection ACB with different analgesic durations on TKA patients. Methods: This randomized controlled double‑blinded trial enrolled 90 patients undergoing primary TKA. Participants were randomized to receive ACB with either liposomal bupivacaine (LB), ropivacaine (15 mL of 0.3%), or in the control group, with 30 patients in each group. The primary end points included the static and dynamic visual analog scale (VAS) scores at 24 hours postoperatively. The secondary end points examined the static and dynamic pain scores at 6,12,48, and 72 hours postoperatively; the knee range of motion (ROM); quadriceps muscle strength; duration to first ambulation; opioid consumption; and related adverse events. Results: Patients administered a LB single-injection ACB (LB-ACB) demonstrated significantly reduced VAS scores at static and dynamic phases at 24 hours, relative to the ropivacaine single-injection ACB (R-ACB) and control group patients. We recorded a median interquartile range [IQR] of 1 (0.0– 2.0 [0– 4]) vs. 3 (2.0– 4.0 [0– 5]) vs. 3 (2.0– 4.0 [0– 6]) for static pain scores and 2.5 (1.0– 3.25 [0– 5]) vs. 4 (4.0– 5.0 [2– 7]) vs. 5 (4.0– 6.0 [3– 7]) for dynamic pain scores ( P < 0.001). Both LB-ACB and R-ACB groups showed lower pain scores at 6 and 12 hours postoperatively versus control ( P < 0.05). Time to first rescue analgesia was prolonged in the LB group, and LB-ACB also improved early quadriceps strength and knee ROM. No significant adverse events or motor blockade occurred. Conclusion: Among patients undergoing TKA, LB single-injection ACB offers a significant analgesic advantage compared to ropivacaine, lasting up to 24 hours. After 48 hours, there is no difference in analgesic effects when compared to the control group. Plain Language Summary: 1. Herein, we employed a stringent double-blind protocol, a rather rare approach in liposomal bupivacaine-related research for adductor canal block (ACB) in total knee arthroplasty (TKA) patients.2. This investigation demonstrates the result of various analgesic durations of local anesthetics on the efficacy of ACB following TKA. Comparing the liposomal bupivacaine and ropivacaine groups against the control group, we demonstrated that the local anesthetic analgesia duration is a critical modulator of ACB efficacy evaluation. Keywords: arthroplasty, replacement, knee, liposomal bupivacaine, nerve block, pain, postoperative