Effect of morphine added to multimodal cocktail on infiltration analgesia in total knee arthroplasty: A meta-analysis of randomized controlled trials.

BACKGROUND: The local injection of multimodal cocktail is currently commonly used in the treatment of postoperative pain after total knee arthroplasty (TKA). It is still inconclusive whether the morphine added to the intraoperative injection mixture could make some difference. This meta-analysis aimed to evaluate the efficacy and safety of additional morphine injection on postoperative analgesia in TKA, and provide some useful information on morphine usage in clinical practice. METHODS: The randomized controlled trials (RCTs) in databases including PubMed, Web of Science, Embase, Cochrane Library, Chinese biomedical literature database (CBM), and Chinese National Knowledge Infrastructure (CNKI) databases were systematically searched. Of 623 records identified, 8 RCTs involving 1093 knees were eligible for data extraction and meta-analysis according to criteria included. RESULTS: Meta-analysis showed that the use of local morphine injection was not associated with significant pain relief within 48 hours postoperatively at rest and on motion (P > .05, all). The use of morphine reduced postoperative total systemic opioids consumption (P < .05). This study found no significant differences in other outcomes including knee flexion range of motion (ROM) (P > .05), extension ROM (P > .05), The Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores (P > .05), Post-operative nausea and vomiting occurrence (P > .05) regardless of the presence of morphine or not in the injections. CONCLUSION: Additional morphine added to multimodal cocktail did not decrease the postoperative pain scores significantly based on our outcomes, but it reduced the systemic postoperative opioids consumption in total knee arthroplasty.