Does intraarticular morphine improve pain control with femoral nerve block after anterior cruciate ligament reconstruction?

In a prospective, randomized, double-blinded manner, we compared the effects of a preoperative intraarticular injection of morphine (5 mg) or a placebo, combined with a postoperative femoral nerve block, on postoperative pain. Sixty-two patients underwent an arthroscopically assisted anterior cruciate ligament reconstruction using patellar tendon autograft under general anesthesia. No statistical difference between the two groups was evident in terms of age, sex, weight, operative time, volume of bupivacaine received with the femoral nerve block, or tourniquet use or tourniquet time. Comparison of visual analog scale pain scores revealed no statistical difference between the groups at any point after the operation. Both groups had a significant decrease in visual analog scale scores after the femoral nerve block, with the lowest mean values 4 hours after the operation (morphine group, 1.7; placebo group, 1.4), and continuing to be significantly less through 24 hours (morphine, 2.6; placebo, 2.9). No significant difference in postoperative narcotic medication use was evident in the recovery room or at home. A post hoc power analysis revealed that the study power reached 87%, with a significance level of 5%. The postoperative femoral nerve block was effective, and intraarticular morphine provided no additional benefit.