Sleep hormone melatonin tested to stop Post-Surgery confusion in seniors

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Demographic criteria: patient 70 years old or older * Diagnostic criteria: isolated fracture of a lower limb * Proximal femoral fractures: head, cervical, or trochanteric fractures * Periprosthetic hip fracture * Femoral shaft fracture * Distal femoral fractures: supracondylar or condylar * Periprosthetic knee fracture * Tibial plateau fracture * Treatments/strategies/procedures: scheduled orthopedic surgery (osteosynthesis or arthroplasty) * proxy or care giver knowing baseline cognitive status of the patient present or reachable by phone for an interview Exclusion Criteria: * Patient already taking Melatonin * Contraindications and precaution for use of Melatonin administration: * Hypersensitivity to the active substance or to any of the excipients of Circadin© * Liver failure (presence of some of the following clinical and biological symptoms: icterus, asterixis, ascites, known esophageal varices, total bilirubin \>20 micromol/L, FV \<70%), * Cirrhosis (known histological liver fibrosis) * Renal failure with clearance \<30 ml/min O Autoimmune disease O Hereditary galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption syndrome * Patients taking fluvoxamine, 5- or 8-methoxypsoralen, cimetidine, oestrogenotherapy, quinolones, carbamazepine, rifampicin * Other concomitant trauma than lower limb fracture(s) * Surgery scheduled in more than 5 days * Patient under mechanical ventilation * Patient refusing to participate * Patient not talking / understanding French (delirium assessment impossible) * Patient already participating to another interventional study * No signed informed consent, * No affiliation to a social security regime Secondary Exclusion Criteria: Secondary exclusion (before randomization): diagnosis of delirium at the CAM assessment at inclusion, or creatinin clearance \<30 ml / min and /or biological signs of hepatocellular insufficiency (bilirubin\> 20 umol/l and factor V \<70%) if samples not available during the anesthesiologist consultation and so performed after inclusion.