Prevention of Rebound Pain After Orthopaedic Surgery With Peripheral Nerve Block (REBOUND)_part B

This study contains two parts, one for the upper limb and one for the lower limb. Eachpart will be published independently.This registration concerns the lower limb cohort.Patients from each cohort (upper limb and lower limb) will be randomized into two groupsof 25 patients each, for a total enrollment plan of 50 patients per cohort. After writteninformed consent, patients will be allocated to one of the two groups according to acomputer‐generated randomization list.In the control group, morphine will be administered exclusively on demand via oralPCA,based on pain intensity assessed using a numeric rating scale (VAS > 4). For oralPCA, one10 mg morphine tablet is placed on the patient's bedside table by the nursingstaff. When the patients experience pain, they may take the tablet autonomously andsubsequently inform the nurse, who then prepares and places a new tablet at bedside forthe next potential pain episode. No scheduled or prophylactic opioid administration willbe provided in this group. The maximal allowed dose through oral PCA will be 6 tablets(10mg each) per 24‐hour period.In the intervention group, morphine will be administered at predefined regular intervals,starting immediately in the postoperative period in addition to the availability of oralPCA morphine as mentioned above. Scheduled doses of 20mg slow‐release oral morphine willbe given at fixed 12 hour intervals. Patients will therefore receive regular morphine toensure continuous baseline analgesia while still having access to an additional tabletvia oral PCA in case of breakthrough pain, following the same nursing procedure as in thecontrol group.In both groups, standardized multimodal analgesia will be providedThe primary objective of this study is to assess and compare the highest pain scorewithin the first 24 postoperative hours between the two groups using the Visual AnalogScale (VAS). The secondary objective is to assess the effect of the intervention onpostoperative pain and analgesic outcomes, including morphine consumption, pain scores,need for additional nerve blocks, incidence of chronic pain, duration of analgesia,postoperative side effects, complications, and hospital length of stay.