A comparison of three techniques for analgesia following total knee joint replacement: Continuous femoral nerve block or spinal morphine or a combination.

This prospective randomised controlled study has been designed to compare analgesia and side-effects of continuous femoral nerve block, spinal morphine and both combined. All patients will receive a spinal anaesthetic with 15-20mgs of bupiviacaine. Patients allocated to the continuous femoral nerve block group will have a femoral nerve block establised using a arrow StimuCath Continuous Nerve Block Kit and ropivacaine 0.75% with adrenaline 5mcg/ml. Patients who are allocated to the spinal morphine group or combination group will have 175mcg preservative-free morphine added to their spinal anaesthestic. Postoperatively, patients who have a continuous femoral nerve block will have an infusion of ropivacaine 0.2% commenced at 12mls per hour until the morning of postoperative day 2. All patient will have an intravenous patient controlled analgesia (PCA) infusion of morphine commenced on 1mg boluses with a lockout period of 7 minutes until the morning of postoperative day 2.