A Study to Evaluate the Efficacy and Safety of Fondaparinux for the Prevention of Venous Blood Clots in Patients With a Plaster Cast or Other Type of Immobilization for a Below-knee Injury Not Needing Surgery

Inclusion Criteria: * Requiring rigid or semi-rigid immobilization (e.g. with a plaster cast or brace) for at least 21 days and up to 45 days because of isolated non-surgical below-knee injury * With a no weight-bearing recommendation at the time of inclusion (partial weight bearing is permitted e.g. crutches, walking cast, relief shoes), * Presenting at least one of the following risk factors for venous thromboembolism: below-knee fracture or Achilles tendon rupture, age ≥40 years, body mass index \> 30 kg/m2, oestrogen-containing hormonal replacement therapy or oral contraception, active cancer (treatment ongoing or stopped for less than one year), history of VTE, congenital or acquired hypercoagulable state, * Requiring thromboprophylaxis according to the Investigator's judgement up to complete mobilization (corresponding to cast or brace removal) * Able and willing to provide written informed consent Exclusion Criteria: * Delay between injury and randomization greater than two days, * Treatment with antithrombotic or anticoagulant therapy, including low-dose anticoagulation, for more than 2 days prior to randomization, * Anticoagulant therapy required or likely to be required during the study period for another reason (e.g. planned surgery justifying pharmacological thromboprophylaxis, curative dose for treatment of VTE, etc.) * Known hypersensitivity to fondaparinux or nadroparin or their excipient, * Known history of heparin-induced thrombocytopenia, * Women of child…