Continuous femoral nerve block is more effective than continuous adductor canal block for treating pain after total knee arthroplasty: A randomized, double-blind, controlled trial

Abstract

Objectives: Previous studies comparing adductor canal block (ACB) with femoral nerve block (FNB) are inconclusive with regard to patient-controlled analgesia (PCA) induced by opioids. Moreover, some postoperative pain severity results differ between previous randomized controlled trials (RCTs). The primary aim of the current study was to compare total intravenous morphine consumption administered via PCA during the first postoperative day in continuous FNB and ACB groups after total knee arthroplasty (TKA). Secondary aims included evaluation of postoperative pain via a visual analog scale, degree of knee extension, quadriceps muscle strength, and ability to sit, stand upright, and walk.

Methods: The study was a RCT. Inclusion criteria were presence of gonarthrosis, age >18 and <75 years, and scheduled for TKA under single-shot spinal anesthesia.

Results: A number of morphine uses was lower in the FNB group than in the ACB group (14, range 12-15 vs 20, range 18-22; P = .0001), and they perceived less severe pain at the 8th (P = .00003) and 24th hours. However, ACB was significantly superior with regard to most of the other parameters pertaining to mobility, including muscle strength at the 8th and 24th hours, degree of knee extension at the 8th hour, sitting at the 8th hour, standing upright at the 24th hour, and walking at the 24th and 48th hours.

Discussion: FNB was associated with the perception of less severe pain after TKAs. However, ACB was associated with earlier mobility rehabilitation.

Figure 1

A. Ultrasound scanning before catheter implantation. B. Local anesthetic deposition in the area of saphenous nerve. ALM = adductor longus muscle, LA = local anesthetic, SaM = sartorius muscle, SaN = saphenous nerve, SFA = superficial femoral artery, VMM = vastus medialis muscle.

Figure 2

Pain severity presented on visual analog scale (VAS) in 2 groups of patients. Pain intensity was measured at 8th, 24th, 48th hours, and before patient discharge. Data are presented as means and confidence intervals. ∗ denotes probability below .05.