Is sciatic nerve block advantageous when combined with femoral nerve block for postoperative analgesia following total knee arthroplasty? a meta-analysis

Background Total knee arthroplasty (TKA) is associated with moderate-to-severe postoperative pain despite the use of femoral nerve block (FNB). The analgesic benefits of adding sciatic nerve block (SNB) to FNB following TKA are unclear. The aim of this meta-analysis was to quantify the analgesic effects of adding SNB to FNB following TKA. Methods We searched the US National Library of Medicine (MEDLINE), Excerpta Medica (Embase), and Cochrane Central Controlled Trials Register databases in March 2015 for randomized and quasi-randomized controlled trials (RCTs) that evaluated the analgesic advantages of adding SNB to FNB compared to FNB alone after TKA. The designated primary outcome was intravenous morphine consumption during the 24-hr postoperative interval. The severity of pain was evaluated at rest and with movement two, four, eight, 12, 24, 36, and 48 hr postoperatively. Morphine consumption during the postoperative 24-48 hr interval, time to first analgesic request, opioid-related side effects, block-related complications, patient satisfaction, functional recovery, and time to hospital discharge were also evaluated. Trials were stratified based on whether a single-shot SNB (SSNB) or continuous SNB (CSNB) was used. Data were combined using random effects modelling. Results Eight RCTs, including 379 patients, were analyzed. Five trials examined SSNB, and three assessed CSNB. Together, SSNB and CSNB reduced the 0-24 hr weighted mean difference [95% confidence interval] of morphine consumption by 10.6 [−20.9 to −0.3] mg ( P = 0.042; I 2 = 97%) and 20.5 [−28.6 to −12.4] mg ( P < 0.001, I 2 = 86%), respectively. SSNB reduced pain at rest and during movement up to 8 hr postoperatively ( P = 0.023 and P < 0.001, respectively), whereas CSNB reduced pain at rest up to 36 hr ( P = 0.004) and pain with movement up to 48 hr ( P = 0.031). CSNB also decreased the odds of postoperative nausea and vomiting by 91% ( P = 0.011). Conclusion The available evidence supporting the analgesic benefits of adding SNB to FNB following TKA is marked by significant heterogeneity. With this challenge in mind, our meta-analysis suggests that SNB can significantly reduce postoperative opioid consumption and diminish knee pain following TKA compared to no SNB in the setting of FNB.