With a power of 80% and a significance level of 5% we need 64 patients (32 in each arm) to show a 30% reduction in postoperative pain during the first 3 postoperative days with 5 measurements and we need 42 patients (21 in each arm) to show a 15% increase in the QoR-15 during the first 3 postoperative days. With an anticipated loss to follow up of 20% we need 80 patients ( 40 in each arm).