Abstract: BACKGROUND: Effective analgesia after total knee arthroplasty is crucial for rehabilitation, with adductor canal block being a commonly used method. Traditional single-injection local anesthetics provides limited analgesic duration, and continuous catheter infusion exhibits complexity and high cost.  
OBJECTIVE: To compare the efficacy and safety of a single injection of liposomal bupivacaine versus continuous catheter infusion of ropivacaine hydrochloride for adductor canal block analgesia after total knee arthroplasty.  
METHODS: Eighty patients undergoing primary unilateral total knee arthroplasty at Gaoyou People’s Hospital from March 2024 to February 2025 were randomly assigned to two groups: the liposomal bupivacaine group and the continuous infusion group. The liposomal bupivacaine group received a single adductor canal block injection of 133 mg (10 mL) liposomal bupivacaine mixed with 5 mL of 0.75% ropivacaine hydrochloride postoperatively. The continuous infusion group received an adductor canal block catheter placed near the saphenous nerve, connected to an analgesic pump delivering 0.25% ropivacaine hydrochloride (loading dose: 10 mL; infusion rate: 6 mL/h). Analgesic efficacy was assessed by comparing pain scores at various time points postoperatively, postoperative analgesia-free duration, morphine rescue consumption, and postoperative walking distance in both groups. Safety was evaluated by monitoring complications. Additionally, procedural time, cost, patient satisfaction, and hospital stay were compared between the two groups.  
RESULTS AND CONCLUSION: (1) Pain scores at rest and during movement showed no significant differences between liposomal bupivacaine group and continuous infusion group at 6, 12, 24, 48, and 72 hours postoperatively (P > 0.05). The postoperative analgesia-free duration was 19 hours in the liposomal bupivacaine group and 22 hours in the continuous infusion group (P > 0.05). (2) Within 72 hours postoperatively, the liposomal bupivacaine group required an average of 78.6 morphine rescue treatments, while the continuous infusion group required 80.5, without significant differences (P > 0.05). (3) Procedural time was significantly shorter in the liposomal bupivacaine group (6.1±1.4 min) than in the continuous infusion group (20.3±1.2 min, P < 0.05). (4) No differences were observed in patient satisfaction, hospital stay, or walking ability (P > 0.05). (5) One case of quadriceps paralysis occurred in the continuous infusion group at 6 hours postoperatively but resolved spontaneously without further complications. Each patient in the liposomal bupivacaine group saved 132 RMB in analgesia-related costs. (6) It is concluded that within 72 hours after total knee arthroplasty, single-injection liposomal bupivacaine provided comparable analgesia to continuous ropivacaine infusion in terms of pain scores, postoperative analgesia-free duration, and morphine rescue requirements. Hospital stay, patient satisfaction, and functional recovery were similar. However, single-injection liposomal bupivacaine adductor canal block is more convenient, saves time, and reduces costs. 

Key words: liposomal bupivacaine, continuous infusion, total knee arthroplasty, adductor canal block, postoperative analgesia