Local Infiltration Analgesia or Intrathecal Morphine in Total Knee Arthroplasty

The purpose of this study is to determine whether local infiltration analgesia is more effective than intrathecal morphine in reducing postoperative pain in total knee arthroplasty.

Postoperative pain is often severe following total knee arthroplasty. Spinal anesthesia is a common method in total knee arthroplasty. Adding morphine to the local anesthetic injected intrathecally prolongs the analgetic effect, but may give the usual opioid side effects. The Local Infiltration Analgesia (LIA) technique has proven effective in reducing postoperative pain in total knee arthroplasty. In the LIA technique a long-acting local anesthetic (ropivacaine), a nonsteroidal anti-inflammatory drug (ketorolac), and epinephrine are infiltrated intraoperatively and via an intraarticular catheter postoperatively. The aim of this study is to evaluate if spinal anesthesia together with the LIA technique provide better postoperative pain relief and mobilization than spinal anesthesia with addition of morphine to the local anesthetic intrathecally. Primary end-point is morphine consumption the first 48 postoperative hours. Secondary end-points are pain intensity, knee function, time to home readiness, hospital stay, side effects and patient satisfaction. Patients are followed up to 3 months after surgery.

Spinal injection: bupivacaine 17.5 mg (3,5 mL) + 0.25 mL 0.9% saline. Local Infiltration Analgesia: 400 mg ropivacaine, 30 mg ketorolac and 0.5 mg epinephrine (total volume 166 ml) are infiltrated by the surgeon into the soft tissues peri-articularly during the operation. On the first and on the second postoperative morning, 200 mg ropivacaine, 30 mg ketorolac and 0.1 mg epinephrine, total volume 22 ml, are injected intraarticularly via the catheter.

Spinal injection: bupivacaine 17.5 mg (3.5 mL) + 0.1 mg (0.25 mL) morphine. No intraarticular injections are given.

Inclusion Criteria: Patients scheduled for total knee arthroplasty under spinal anesthesia. Aged 40-85 yrs. ASA physical status I-III and mobility indicating normal postoperative mobilization. Exclusion Criteria: Known allergy or intolerance to one of the study drugs. Serious liver-, heart- or renal decease. Rheumatoid arthritis. Chronic pain or bleeding disorder.