The role of sciatic nerve block to complement femoral nerve block in total knee arthroplasty: a meta-analysis of randomized controlled trials.

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Femoral nerve block (FNB) appears to have higher postoperative analgesic benefits compared with the patient-controlled analgesia (PCA) in total knee arthroplasty (TKA). However, the role of sciatic nerve block (SNB) as a complement to FNB remains controversial. We performed a meta-analysis assessing the benefits of the SNB as a complement to FNB, as well as comparing the efficacy of single-injection versus continuous SNB in TKA. Our group conducted a systematic literature search in PubMed, EMBASE and Google Scholar. We retrieved randomized trials comparing either SNB versus placebo or continuous versus single-injection SNB. The intervention group was the use of SNB as a complement to FNB, while the control group was FNB alone. Pain score at rest and movement (at 4, 12, 24, 48 and 72h), patient-controlled intravenous opioid consumption, length of hospital stay, and incidence of nausea were extracted from each study. Random-effects model was used for meta-analysis and standardized mean difference (SMD) was used as the effect size. Ten articles comprising 514 patients were included to compare the effects of SNB combined with FNB versus FNB alone. Interventional group was found to significantly reduce pain score at for 4h (SMD = -0.94, 95% CI -1.42 to -0.47, P < 0.001, I2 = 76.5%) compared with the control group. Pain score at rest was significantly reduced at movement for 12h (SMD = -0.29, 95% CI -0.54 to -0.04, P = 0.02, I2 = 0%). Opioid consumption was significantly reduced at 24 (SMD = -0.60, 95% CI -1.01 to -0.17, P = 0.01, I2 = 69.1%) and 48h (SMD = -1.04, 95% CI -1.46 to -0.61, P < 0.001, I2 = 43.4%) after TKA using SNB as a complement to FNB. Three articles were additionally meta-analyzed to compare the efficacy of single-injection (n = 79) versus continuous SNB (n = 79), being the latter one significantly associated with less pain score at 24 (SMD = -0.77, 95% CI -1.10 to -0.45, P < 0.001, I2 = 0%) and 48h (SMD = -0.69, 95% CI -1.01 to -0.36, P < 0.001, I2 = 0%), but not at 12h (SMD = -0.34, 95% CI -0.73 to -0.06, P = 0.10, I2 = 0%). This meta-analysis provides evidence-based supports to the benefits of SNB as a complement to FNB in TKA. The combination sciatic-femoral nerve block appears to be the optimal choice for patients in high risk of postoperative opioids consumption or acute pain after TKA.