Comparative Effectiveness of Pulmonary Embolism Prevention After Hip and Knee Replacement

Inclusion Criteria:

   1. 21 years of age or older;

   2. Undergoing elective primary, revision or second stage re-implantation total hip/knee
   replacement or uni-compartmental knee replacement or hip resurfacing arthroplasty;

   3. Has necessary mental capacity to participate and is able to comply with study protocol
   requirements;

   4. Eligible for randomization to at least two of the three study regimens;

   5. Is not pregnant on the day of surgery;

   6. Has signed the consent form; and

   7. Is willing to be randomized and participate in the study.

Exclusion Criteria:

   1. Undergoing bilateral hip or knee replacement;

   2. Has been previously enrolled;

   3. Is pregnant or breastfeeding;

   4. Is on chronic anticoagulation other than antiplatelet medications;

   5. Concurrently enrolled in another active interventional clinical trial testing a drug
   or intervention known or believed to interact with aspirin, warfarin, or rivaroxaban;

   6. Has documented gastrointestinal, cerebral, or other hemorrhage within 3 months;

   7. Has a known diagnosis of defective hemostasis and past history of clinical bleeding
   requiring transfusion and treatment;

   8. Has had an operative procedure involving the eye, ear, or central nervous system
   within one month;

   9. Has uncontrolled hypertension with systolic BP > 220mmHg or diastolic BP > 120mmHg;

10. Body weight of less than 41 kilograms at baseline visit;

11. Member of a vulnerable patient population.