The primary objective is to:

• demonstrate the efficacy of SR123781A in the prevention of venous thromboembolism (VTE) by the demonstration of a dose-response in patients undergoing total hip replacement surgery.

The secondary objectives are to:

• evaluate the safety of SR123781A in the prevention of VTE after elective total hip replacement surgery; and
• to assess the SR123781A pharmacokinetic profile in patients undergoing elective total hip replacement surgery.

Inclusion Criteria:

• Patients scheduled to undergo elective total hip replacement surgery or a revision of at least one component of a total hip replacement performed > 6 months prior to study entry

Exclusion Criteria:

• Pregnant or nursing women, or women of childbearing potential who are not using an effective contraceptive method and who do not have a negative pregnancy test performed immediately before randomization
• Known progressive malignant disease
• Ischemic stroke in the last 3 months
• Myocardial infarction (MI) in the last 3 months
• Any major orthopedic surgery in the 3 months prior to study start
• Clinical signs or symptoms of DVT or PE within the last 12 months or symptoms of post phlebitic syndrome (these conditions may confound DVT/PE assessments)
• Treatment with other antithrombotic agents within 7 days prior to surgery