Liposomal bupivacaine versus ropivacaine in four-in-one nerve block for total knee arthroplasty: a randomized controlled trial.

BACKGROUND: Effective postoperative pain control following total knee arthroplasty (TKA) is essential to enhance for early functional recovery. Liposomal bupivacaine (LB) is a sustained-release formulation of bupivacaine is used to prolong analgesia after regional nerve block. This study evaluated the analgesic efficacy of a single injection of LB for a four-in-one nerve block after TKA. METHODS: Between September 2023 and July 2024, 120 patients aged 65-80 years undergoing unilateral TKA under spinal anesthesia were randomized into two groups: LB (n = 60) and RP (ropivacaine, n = 60). This was a randomized, single-blinded trial. In the post-anesthesia care unit, a four-in-one nerve block was performed under ultrasound guidance using either LB or RP. The primary endpoint was the visual analog scale pain score at rest (VAS-R) at 72 h postoperatively. Secondary outcomes included the visual analog scale pain score during movement (VAS-M) over 72 h, opioid consumption on Post Operative Day 1-3 (POD1-3), muscle strength (Medical Research Council [MRC] scale) over 72 h, range of motion (ROM), and length of hospital stay (LOS). RESULTS: Over time, VAS-R and VAS-M from 24 to 72 h postoperatively were significantly lower in the LB group compared with the RP group (P < 0.001), effect size analysis revealed moderate effects (r = 0.53-0.88). But the effects in VAS-R and VAS-M within 12 h postoperatively and the VAS-R AUC over 72 h revealed small effects (r = 0.20-0.45). No opioid consumption was recorded in either group on POD 1, whereas opioid consumption was lower in the LB group on POD2 and POD3 (P < 0.001). Knee ROM and Medical Research Council (MRC) grades were higher in the LB group during the first 72 h postoperatively (P < 0.001). LOS did not differ between groups (P = 0.980). Prolonged numbness occurred in 5 patients (8.3%) in the LB group and in none of the RP group, although the between-group difference was not statistically significant. CONCLUSION: In patients undergoing four-in-one nerve block after TKA, a single injection of LB provided statistically significant but modest improvement in analgesia, particularly between 24 and 72 h postoperatively. LB was also associated with lower opioid consumption on POD2-3 and better early functional recovery. However, the clinical significance of these findings remains uncertain. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2500102073. Reg Date 08/05/2025. Retrospectively registered.