Adductor canal blocks (ACBs) are an alternative to femoral nerve blocks that minimize lower extremity weakness. However, it is unclear whether this block will provide analgesia that is equivalent to techniques, such as epidural analgesia. The purpose of this randomized controlled trial was to compare continuous ACBs with epidural analgesia for primary total knee arthroplasty.
Following institutional review board approval, 145 patients were randomized to 1 of 3 groups: combined spinal-epidural (CSE), spinal + continuous ACB (CACB), or general + CACB. Epidural analgesia was used postoperatively in the CSE group, and an adductor canal catheter was used in the CACB groups. Power analysis determined that 84 patients per group were needed to demonstrate a 35% increase in ambulation with an alpha of 0.05 at a power of 90%.
At interim analysis, 13 patients were removed for protocol deviations, leaving 45 in CSE, 41 in spinal + CACB and 46 in general + CACB groups. Patient demographics were similar in all comparisons suggesting appropriate randomization. Patients in the CACB groups walked further on postoperative day 1, 2, and 3 (P = .02). Mean daily pain scores were lower in the CACB groups (4.1 CSE, 3.0 spinal + CACB, 3.4 general + CACB, P = .009). There was no significant difference in total opioid consumption between groups (158 morphine equivalents CSE, 149 spinal + CACB, and 172 general + CACB). More patients reported being “very satisfied” in CACB groups (68% general + CACB, 63% spinal + CACB, and 36% CSE; P = .001).
Continuous adductor analgesia provides superior ambulation, lower pain scores, faster discharge, and greater patient satisfaction when compared to epidural analgesia for primary total knee arthroplasty.