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

INTRODUCTION: 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.

METHODS: 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 72 h), 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.

RESULTS: 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 4 h (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 12 h (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 48 h (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 48 h (SMD = - 0.69, 95% CI - 1.01 to - 0.36, P < 0.001, I2  = 0%), but not at 12 h (SMD = - 0.34, 95% CI - 0.73 to - 0.06, P = 0.10, I2  = 0%).

CONCLUSIONS: 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.