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Patient Evidence Summary
Doctor, I have an arm or leg fracture, and require surgery. Will taking aspirin protect me from having a blood clot?
Aspirin is not as effective as an injection blood thinner at preventing DVT after an arm or leg fracture that required surgery.
Study highlights
People with an arm or leg fracture requiring surgery who took aspirin had a higher risk of having a DVT than people taking an injection blood thinner. Death was very rare and similar in both study groups. Aspirin did not result in lower rates of bleeding than the injection blood thinner.
Understanding the problem
When people develop a fracture of their arm or leg or pelvic fracture, there is a risk of developing blood clots in the veins of the arms or legs (DVT) or in the lungs (PE).
For this reason, patients who have a fracture are often started on blood thinners, especially if their fracture requires surgery. The blood thinner is usually an injection under the skin called low-molecular-weight heparin (LMWH).
However, some recent studies have tested whether taking aspirin is as effective as LMWH in preventing blood clots after hip or knee replacement surgery. Aspirin pills are easier to take, and for this reason, are often preferred by patients. Aspirin may also cause less bleeding from the surgical wound which means it may also be preferred by surgeons.
Researchers in this study wanted to find out whether taking aspirin was just as effective as LMWH injections for preventing death and blood clots in patients with arm or leg fractures requiring surgery, or pelvic fractures.
Who? The study included 12,211 adults (average age 44 years old; 38% female) who had a fracture of the arms or legs which required surgery, or pelvic fractures.
People who had a history of blood clots or were already on blood thinners were excluded from the study. People who were younger than 18, pregnant or breastfeeding, had severe kidney disease, or presented to hospital more than two days after the fracture were also excluded from the study.
What? The study compared aspirin to LMWH injections.
Aspirin | vs | Low-molecular-weight heparin |
|---|---|---|
Aspirin 81 mg twice daily in hospital (average of 4 days but varied in different hospitals) followed by an average of 21 days after discharge. | Enoxaparin subcutaneous (under the skin) injections 30 mg twice a day in hospital (average of 4 days) followed by an average of 21 days after discharge. |
Aspirin vs LMWH injections in people who have a fracture of an arm or leg requiring surgery or a pelvic fracture
Outcomes at 90 days | Rate of events with Aspirin | Rate of events with LMWH injections | Results |
|---|---|---|---|
Death from any cause | 78 out of 10,000 people | 73 out of 10,000 people | No effect* |
Death related to pulmonary embolism | 7 out of 10,000 people | 8 out of 10,000 people | No effect* |
| Pulmonary embolism (PE) | 149 out of 10,000 people | 149 out of 10,000 people | No effect* |
| Deep vein thrombosis (DVT) | 251 out of 10,000 people | 171 out of 10,000 people | About 80 more people out of 10,000 had a blood clot in the leg with taking aspirin compared to taking LMWH |
| Bleeding complications | 1,372 out of 10,000 people | 1,427 out of 10,000 people | No effect* |
*Although the rates for the 2 groups look different, the differences were not statistically significant—this means that the difference could simply be due to chance rather than due to the different treatments.
This Evidence Summary is based on the following article:
O'Toole RV, Stein DM, O'Hara NN, et al. Aspirin or Low-Molecular-Weight Heparin for Thromboprophylaxis after a Fracture. N Engl J Med. 2023 Jan 19;388(3):203-213. doi: 10.1056/NEJMoa2205973. PubMed
James Shih
James Shih is a 2nd year Internal Medicine Resident at McGill University. He completed medical school at the University of British Columbia. His research interests include the risk factors for venous thromboembolism, particularly at the population scale. He is currently working with Dr. Susan Kahn on a project to explore how rating scales for post-thrombotic syndrome perform in patients of differing ethnoracial backgrounds.
Bill Geerts, MD, FRCPC
Dr. Bill Geerts is Professor of Medicine at the University of Toronto and a Thromboembolism consultant at Sunnybrook Health Sciences Centre. He is an active member of Thrombosis Canada.
Published: Thursday, June 29, 2023
Please note that the information contained herein is not to be interpreted as an alternative to medical advice from a professional healthcare provider. If you have any questions about any medical matter, you should consult your professional healthcare providers, and should never delay seeking medical advice, disregard medical advice or discontinue medication based on information provided here.
, McMaster University