PCORI has identified the need for large studies that look at real-life questions faced by diverse patients, caregivers, and clinicians. To address this need, PCORI launched the Pragmatic Clinical Studies initiative in 2014. Pragmatic clinical studies allow for larger-scale studies with longer timelines to compare the benefits and harms of two or more approaches known to be effective for preventing, diagnosing, treating, or managing a disease or symptom. They focus on everyday care for a wide range of patients. This research project is one of the studies PCORI awarded as part of this program.

This research project is in progress. PCORI will post the research findings on this page within 90 days after the results are final.

What is the research about?

Nearly 1 million hip replacement and knee replacement surgeries take place in the United States each year. A small number of patients develop blood clots in their lungs or legs. These clots cause between 1,000 and 5,000 deaths each year. Medicines called blood thinners can lower a person’s risk of forming a blood clot after surgery. But blood thinners can also raise the chance of serious or uncontrolled bleeding. Bleeding problems can cause pain and stiffness or affect how well a replaced joint works. Bleeding problems can also cause an infection that may require surgery to remove the replaced hip or knee joint.

Doctors don’t know how best to balance preventing blood clots against the chance of bleeding problems in patients who have hip or knee replacement surgery. Previous studies have shown that different blood thinners carry different risks of causing bleeding problems. Some guidelines recommend using strong blood thinners after knee or hip replacement surgery; others recommend weaker ones because of the chance of bleeding.

Because it’s so uncommon for a patient to die from a blood clot after hip or knee replacement surgery, earlier studies didn’t have enough patients to help researchers identify which blood thinners work best to save lives. This study is large enough to compare differences in the rates of blood clots and mortality after hip and knee replacement surgery among the three most commonly used blood thinners; the study is also comparing the medicines’ chances of causing bleeding problems.

Who can this research help?

Information from this study can help people who have hip or knee replacement surgery and their doctors choose a medicine to prevent blood clots.

What is the research team doing?

The research team is recruiting 25,000 patients who are having hip or knee replacement surgery at one of 25 medical centers across the United States. The team is assigning patients by chance to get one of three medicines that are commonly used to prevent blood clots after surgery.

The research team is comparing how many patients in each of the three groups

• Have bleeding problems
• Return to the hospital because of a blood clot in their leg or lung
• Die, even if their death is not related to a blood clot

The research team formed a patient advisory board of people who had had hip or knee replacement surgery. The board includes people who had problems after surgery. The board is helping the research team to understand patients’ views on the benefits and harms of blood thinners.

Research methods at a glance