Continuous Versus Single-Injection Sciatic Nerve Block Added to Continuous Femoral Nerve Block for Analgesia After Total Knee Arthroplasty A Prospective, Randomized, Double-Blind Study

Background and Objectives: The benefit of adding sciatic nerve block (SNB) to femoral nerve block to improve analgesia after total knee arthroplasty (TKA) is uncertain. We hypothesized that the effective duration of single-injection SNB is too short to improve postoperative analgesia and that this contributes to conflicting results on the efficacy of SNB after TKA. We evaluated this hypothesis in a prospective double-blind randomized controlled trial. Methods: Sixty patients undergoing TKA were randomly allocated to a continuous SNB group or a single-injection SNB group. All patients received femoral nerve block (0.5% ropivacaine 20 mL) and SNB (0.2% ropivacaine 20 mL) and catheters were inserted into both peripheral nerve block sites before surgery. Both groups received continuous femoral nerve block and patient-controlled intravenous analgesia with morphine. Continuous SNB (0.2% ropivacaine 5 mL/h; continuous SNB group) or sham continuous SNB (0.9% normal saline 5 mL/h; single-injection SNB group) was provided after surgery. The primary outcome was total morphine consumption for 48 hours after surgery. Results: Total morphine consumption in the 48-hour period after surgery was significantly lower in the continuous SNB group compared with the single-injection SNB group [4.9 (5.9) vs 9.7 (9.5) mg, P = 0.002]. Visual analog scale pain scores at rest were also significantly lower in the continuous SNB group (P = 0.035). Conclusions: The combination of continuous femoral and SNB provides a superior opioid sparing effect and improves analgesia after TKA.