The efficacy of liposomal bupivacaine in parasacral ischial plane block for pain management after total knee arthroplasty: a randomized controlled trial.

Background: Utilizing liposomal bupivacaine (LB) for postoperative analgesia post-total knee arthroplasty (TKA) is prevalent. However, its effectiveness in pain control, specifically in the parasacral ischial plane block (PIPB) post-TKA, remains unknown.

Methods: This single-center, double-blinded, randomized controlled trial recruited patients scheduled for unilateral TKA. Forty-five patients were randomly assigned in a 1:1 ratio to receive 133 mg (Group A) or 266 mg (Group B) LB using the block randomization method. The PIPB effectiveness was assessed by evaluating changes in sensory and motor functions. The primary outcome was the cumulative area under the curve (AUC) of the Numerical Rating Scale (NRS) at rest within 72 h postoperatively. All patients were included in the analyses of analgesic efficacy, rehabilitation quality, and adverse events.

Results: Between January 30, 2024, and May 1, 2024, 45 patients were enrolled and randomly assigned to Group A (n = 22) and Group B (n = 23). A significant between-group difference was observed in the NRS-AUC_0-72 h at rest postoperatively (132.3 ± 19.7 vs. 97.3 ± 19.1, p = 0.001), but none was observed in NRS-AUC_0-72 h during activity (p = 0.642). Kaplan-Meier survival analysis revealed significant between-group differences in the median onset times of sensory [60 vs. 35(min), p < 0.0001] and motor blocks [85 vs. 50(min), p < 0.0001]. The onset time of sensory block was notably shorter than that of motor block in both groups. No significant variance was observed in the median regression time for the sensory block. A significant between-group difference in the rescue analgesic dosage was observed on the first postoperative day [43.1 vs. 27.2(mg), p = 0.009], with no significant differences in the subsequent two days or the total amount. No significant between-group differences were found in adverse events or rehabilitation quality.

Conclusion: LB used in the PIPB was effective for analgesia at rest post-TKA, with 266 mg demonstrating superiority. Trial RegistrationThe randomized controlled trial was registered in the Chinese Clinical Trial Registry (https://www.chictr.org.cn/, No: ChiCTR2400079606).