Sunday 10 December 2023

Aspirin vs Enoxaparin for thromboprophylaxis after a fracture

You are sending home a patient from the ED with a broken ankle after you carefully crafted a new plaster. Hmmmm… do you need to worry about DVT prophylaxis?

Guidelines and local practice vary. When you see this variation, it invariably means there is not conclusive evidence to inform practice.

Perhaps this RCT from the New England Journal of Medicine might help?

These researchers from the USA conducted a pragmatic, multicentre, randomized non-inferiority trial. They included patients who had a fracture of an extremity (hip to midfoot or shoulder to wrist) that were treated operatively or who had pelvic or acetabular fracture.

Patients were randomized to aspirin 81mg BD vs. enoxaparin 30mg BD while in hospital but could get whatever after discharge “according to the clinical protocols of each hospital.” (For what it’s worth, BD aspirin is not a typo…)

Primary outcome was death from any cause and secondary outcomes looked at PE’s, DVT’s and bleeding complications.


12,211 patients were included! Mean age 44 years old and 87% had lower extremity fractures. Median BMI was 27. On average, patients received about 9 in-hospital doses of thromboprophylaxis and were prescribed a 21-day supply of whatever upon discharge.

Primary outcomeno difference at 0.7% mortality in both groups. There was statistically more DVT’s in the aspirin group by a whopping 0.8% margin (NNT 125). PE’s were no different and nor were complications.

What should we conclude in the ED?

Yes, this is the tricky. The patients included in this study were not patients discharged from the ED. Extrapolating the findings from this RCT to our population is problematic. Bummer…

In addition, I’m disappointed they did not standardize the take home thromboprophylaxis. This likely made it much more difficult to find differences between the groups as patients were likely to cross-over.

Further, this trial did not restrict enrollment to high-risk patients. These are precisely the patients I want to target… another bummer. It is very possible that enrolling all-comers diluted down the benefits & differences of therapy. Who knows… but it’s common sense.

In the end, I don’t think this should substantially change how we think about ED patients that we send home with fractures. Nevertheless, I anticipate this study will influence the guidelines… we might see some more aspirin being recommended. But I'm not sure if this is for the better or worse.



METRC Consortium, Aspirin or Low-Molecular-Weight Heparin for Thromboprophylaxis after a Fracture. N Engl J Med 2023;338:203-13. [Link to article]




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