Methods

We conducted a randomized controlled trial in which patients scheduled for simultaneous bilateral TKA were randomly assigned to receive periarticular analgesic injection or epidural analgesia. In the periarticular analgesic injection group, the injection contained 7.5 mg/ml ropivacaine 40 ml, 10 mg/ml morphine hydrochloride hydrate 1.0 ml, 1.0 mg/ml epinephrine 0.6 ml, methylprednisolone 80 mg, and ketoprofen 50 mg. These agents were mixed with normal saline to a combined volume of 120 ml. The 60 ml of the cocktail was injected into each knee. In the epidural analgesia group, the catheter was placed at the L2–3 or L3–4 level, and connected to an infusion pump delivering continuous infusion (flow rate: 4 ml/h) of 100 ml of 2 mg/ml ropivacaine plus 1.0 ml of 10 mg/ml morphine hydrochloride hydrate. Surgery was managed under spinal anaesthesia. Surgical techniques and postoperative medication protocols were identical in both groups. The primary endpoint was postoperative pain at rest, quantified as the area under the curve (AUC) of the score on a visual analogue scale.