Effect of a single shot sciatic nerve block combined with a continuous femoral block on pain scores after total knee arthroplasty. A randomized controlled trial

Abstract

Background and Purpose: Postoperative pain after knee arthroplasty (TKA) is reported as severe in up to 60% of patients. Continuous femoral nerve blocks (CFNB) are a choice for major knee repair, but controversies remain about the need of supplemental sciatic Nerve blocks (SNB) for better analgesia. Our aim is to assess the effect of the association of a SNB to a CFNB to reduce postoperative pain after TKA. Methods: A prospective randomized, single blinded, controlled study, on 50 patients undergoing TKA. Control group received a CFNB before general anesthesia; in the intervention group a single shot SNB was added after the CFNB was done. After the end of surgery all patients started a continuous local anesthetic infusion through the femoral catheter in the PACU (Post-Anesthesia Care Unit). Pain scores were measured in the PACU and at 12h and 24h postoperative using a Visual Analog Scale (VAS). Results: VAS pain scores (mm) were lower and statistically significant for the intervention group up to 12h postoperative: PACU admission mean VAS=59.4 vs. 30.2, p= 0.001; at 12h mean VASr=26.1 vs. 9.2, p=0.006; at 24h mean VASr=30.1 vs. 32.7, p=0.723. Conclusions: The association of a single shot SNB with a CFNB significantly reduces postoperative pain scores after TKA up to 12h. At 24 h there are no differences between groups