The Effects of Intra synovial Ropivacaine and Morphine Injection on Postoperative Pain After Total Knee Arthroplasty

ABSTRACT

PURPOSE: Pain control after total knee arthroplasty reduces total admission days and is important in improving post operative range of motion. This study evaluates the efficacy of intrasynovial injection of morphine and ropivacaine after total knee arthroplasty. MATERIALS AND METHODS: A prospective, double blinded and randomized study was performed in thirty two patients with American society of anesthesiology stage I or II who underwent one staged total knee arthroplasty for both knees simultaneously under spinal anesthesia. Demographic data (age, height, weight, gender distribution, Hospital for Special Surgery knee score, Knee society score, visual analogue scores (VAS) and range of motion were evaluated in all patients preoperatively. Before closure of the joint capsule, a local injective analgesia of 50mL including 0.5 ml 5 mg of HCL morphine, 40 mL 0.6% 300 mg ropivacaine and 0.25 mL of 1200,000 epinephrine was injected into the synovium of one knee and 50 mL of normal saline was injected into the synovium of the opposite knee. Analgesic efficacy was evaluated by visual analogue scores (VAS) at intervals of 2, 4, 6, 12, 24, 32, 40 and 48 hours after operation. During this period, the amount of postoperative bleeding and range of motion were compared between both knees in the same patient. RESULTS: There were no statistically significant differences among both knees in regard to VAS at intervals of 2, 4, 6, 12, 24, 32, 40 and 48 hours after surgery (p>0.05). There were no statistically significant differences between the range of motion among both knees (p>0.05). CONCLUSION: On the basis of the results of this study, we do not recommend the routine use of postoperative intrasy-novial ropivacaine and morphine injection for the purpose of reducing pain in patients undergoing knee arthroplasty under spinal anesthesia with epidural patient controlled anesthesia.