Objective:To compare the analgesic effects of fascia iliaca compartment block with different concentrations of liposomal bupivacaine for total hip replacement in elderly patients.Methods:This was a prospective study. Sixty-four elderly patients of either sex with hip fracture, aged 65-85 yr, with body mass index of 20-30 kg/m 2 and American Society of Anesthesiologists Physical Status classification Ⅰ-Ⅲ, undergoing elective total hip arthroplasty from September to December 2023 in Zhangjiagang Hospital affiliated to Soochow University, were divided into LB1, LB2, LB3 and LB4 groups ( n=16 each) using the random number table method. The fascia iliaca compartment block was performed under ultrasound guidance before anesthesia induction. Liposomal bupivacaine 66.5, 133.0, 199.5 and 266.0 mg diluted to 30 ml in normal saline were given in LB1, LB2, LB3 and LB4 groups, respectively. The consumption of intraoperative sufentanil and remifentanil and tracheal extubation time were recorded. The pain numeric rating scale (NRS) scores at rest and during activity were recorded at 4, 8, 12, 24 and 48 h postoperatively. Parecoxib sodium was intravenously injected when the NRS score≥4, and the use of parecoxib sodium was recorded. The effect of motor nerve block in the affected lower extremity was evaluated using the modified Bromage scale score at 4, 8, 12, 24 and 48 h postoperatively. The first ambulation time and duration of hospitalization were recorded. The scores for patients′ satisfaction with analgesic effects at 48 h after operation and the occurrence of adverse reactions within 48 h after operation were recorded. Results:Compared with LB1 group, the consumption of intraoperative sufentanil and remifentanil was significantly reduced, the tracheal extubation time was shortened, NRS scores at rest at 12, 24 and 48 h after operation and NRS scores during activity at 8, 12, 24 and 48 h after operation were significantly decreased, and the scores for patients′ satisfaction with analgesic effects were increased in LB2, LB3 and LB4 groups, the modified Bromage scale scores were significantly increased at 4 and 8 h after operation, and the first ambulation time and duration of hospitalization were shortened in LB2 group, and the modified Bromage scale scores were significantly increased at 4, 8, 12, 24 and 48 h after operation in LB3 and LB4 groups ( P<0.05). Compared with LB2 group, the modified Bromage scale scores were significantly increased at 12, 24 and 48 h after operation, and the first ambulation time and duration of hospitalization were prolonged in LB3 and LB4 groups ( P<0.05). There was no significant difference in the incidence of postoperative adverse reactions among the four groups ( P>0.05). Conclusions:The optimal concentration of liposomal bupivacaine for fascia iliaca compartment block is 133 mg/30 ml when used for analgesia in elderly patients undergoing total hip replacement.