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 childbearing potential not using a reliable contraceptive method throughout the study period,
• Women pregnant or breast-feeding during the study period.
• Active, clinically significant bleeding,
• Clinically significant bleeding within the past six months,
• Major surgery within the previous three months,
• Intraocular (other than cataract), spinal, and/or brain surgery within the previous twelve months,
• Haemorrhagic stroke within the previous twelve months,
• Severe head injury within the previous three months,
• Documented congenital or acquired bleeding tendency/disorder(s),
• Previous (within 12 months) or active or currently treated peptic ulcer disease,
• Uncontrolled arterial hypertension (systolic blood pressure over 180 mm Hg or diastolic blood pressure over 110 mm Hg),
• Treatment with more than one antiplatelet agents (e.g. clopidogrel and aspirin) at any dose,
• Need for chronic aspirin at doses≥ 325 mg or chronic NSAIDs,
• Bacterial endocarditis,
• Severe hepatic impairment,
• Calculated creatinine clearance < 30 mL/min,
• Thrombocytopenia ( <100x10\_9/L)
• Body weight < 50 kg.
• Any condition that could prevent the patient from providing written informed consent or from adhering to study treatment,
• Life expectancy under six months,
• Participation in any study using an investigational drug during the previous three months,
• Patient in whom V3 is unlikely to be feasible (e.g. patient moving house),
• In France, a subject will not be eligible for inclusion in this study if not either affiliated to or a beneficiary of a social security system. This is an additional exclusion criterion only applying to subjects enrolled in France.