Efficacy of Two Unique Combinations of Nerve Blocks on Postoperative Pain and Functional Outcome After Total Knee Arthroplasty: A Prospective, Double-Blind, Randomized Controlled Study

Background: This study aimed to explore the efficacy of two unique combinations of nerve blocks on postoperative pain and functional outcome after total knee arthroplasty (TKA).

Methods: Patients scheduled for TKA were randomized to receive a combination of adductor canal block (ACB) + infiltration between the popliteal artery and capsule of the posterior knee block (IPACK) + sham obturator nerve block (ONB) + sham lateral femoral cutaneous nerve block (LFCNB) (control group), or a combination of ACB + IPACK + ONB + sham LFCNB (triple nerve block group), or a combination of ACB + IPACK + ONB + LFCNB (quadruple nerve block group). All patients received local infiltration analgesia. Primary outcome was postoperative morphine consumption. Secondary outcomes were the time until first rescue analgesia, postoperative pain assessed on the visual analog scale (VAS), QoR-15 score, functional recovery of knee, and postoperative complications.

Results: Compared with the control group, the triple and quadruple nerve block groups showed significantly lower postoperative morphine consumption (17.2 ± 9.7 mg vs. 11.2 ± 7.0 mg vs. 11.4 ± 6.4 mg, P = .001). These two groups also showed significantly longer time until first rescue analgesia (P = .007 and .010, respectively, analyzed with Kaplan-Meier method), significantly lower VAS scores on postoperative day 1 (P < .01), significantly better QoR-15 scores on postoperative days 1 and 2 (P < .001), and significantly better functional recovery of knee including range of motion (P = .002 and .001 on postoperative days 1 and 2), and daily ambulation distance (P < .001 and P = .004 on postoperative days 1 and 2). However, the absolute change in morphine consumption, VAS scores, and QoR-15 scores did not exceed the reported minimal clinically important differences (MCIDs) (morphine consumption: 10 mg; VAS scores: 1.5 at rest and 1.8 during movement; QoR-15 scores: 8.0). The MCIDs of other outcomes have not been reported in literature. The triple and quadruple nerve block groups showed no significant differences in these outcomes between each other. The three groups did not show a significant difference in complication rates.

Conclusion: Adding ONB or ONB + LFCNB to ACB + IPACK can statistically reduce morphine consumption, improve early pain relief, and functional recovery. However, the absolute change in morphine consumption, VAS scores, and QoR-15 scores did not exceed the MCIDs. Based on our findings and considering the sample size of this study, there is not enough clinical evidence to support the triple or quadruple nerve block use within a multimodal analgesic pathway after TKA.