The efficacy of continuous versus single-injection femoral nerve block in Total knee Arthroplasty: A systematic review and meta-Analysis

Background: Continuous femoral nerve block (cFNB) has been developed to extend the analgesic effect since the efficacy of single-injection femoral nerve block (sFNB) is often limited to approximately 16-24 h. The aim of this meta-Analysis was to validate the add-on effect of cFNB in the setting of a multimodal analgesic protocol. Methods: We performed a comprehensive literature review on Web of Science, Embase, the Cochrane Library and PubMed. Eight randomized controlled trials (N = 626) that compared the efficacy of cFNB with sFNB were included. The primary outcome domains consist of visual analog scale (VAS) score at postoperative 24 and 48 h. The secondary outcome domains include opioid consumption, length of hospital stay and incidence of nausea. Results: Our analysis revealed that cFNB was associated with a lower VAS score at 24 h (SMD:-0.277;95% CI-0.503 to-0.05). However, the difference of VAS score did not meet the minimal clinically importance difference for total knee arthroplasty (TKA). VAS score at 48 h was similar between the cFNB and sFNB group. The cFNB group was associated with less amount of opioids consumed at both 24(SMD:-1.056;95% CI-1.737 to-0.375) and 48 h(SMD:-1.040;95% CI-1.790 to-0.289). Length of hospital stay and incidence of nausea were similar between the two groups. Conclusion: In the setting of a multimodal analgesic protocol, patients might benefit from cFNB with regards to a reduced need of opioids in the early postoperative period. However, we did not find a clinically significant difference in pain scores at different time points between the cFNB and sFNB group. Level of evidence: I; meta-Analysis.