A groundbreaking study found that over-the-counter aspirin is just as effective as injectable blood thinners in preventing clots during surgery to repair bone fractures. The trial, conducted across 21 trauma centers in the U.S. and Canada, involved more than 12,000 patients and is the largest-ever study in orthopedic trauma patients, says Study Finds.

The findings may challenge surgeons to opt for aspirin for their patients instead of the standard practice of administering heparin.

“Many patients with fractures will likely strongly prefer to take a daily aspirin over receiving injections after we found that both gave them similar outcomes for prevention of the most serious outcomes from blood clots,” said principal investigator Dr. Robert V. O’Toole in a university news release from the University of Maryland School of Medicine. “We expect our findings from this large-scale trial to have an important impact on clinical practice that may even alter the standard of care.”

Blood clots cause as many as 100,000 deaths in the U.S., according to the Centers for Disease Control and Prevention. Patients who require surgery for fractures are at an increased risk of developing potentially life-threatening blood clots in the lungs and limbs. Current guidelines call for administering low-molecular-weight heparin to prevent these clots, although smaller clinical trials on total joint replacement surgery suggested a potential benefit of aspirin as a less expensive, widely available option, says the news release.

The main finding of the study was that giving aspirin to these patients was no worse than administering heparin in preventing death from any cause. The study found that 47 patients in the aspirin group died, compared to 45 patients in the heparin group. For other crucial complications the researchers found no difference between the two groups in clots in the lungs, called pulmonary embolisms. The incidence of bleeding complications, infection, wound problems, and other adverse events from the treatments were similar in both groups.

The only disparity between the aspirin and heparin patients was in blood clots in the legs, called deep vein thrombosis. While the incidence was rare in both groups, patients receiving aspirin had a 2.5% prevalence, while the heparin group only had 1.7% of patients experiencing blood clots in the legs.

“This relatively small difference was driven by clots lower in the leg, which are thought to be of less clinical significance and often do not require treatment,” said the study’s co-principal investigator, Dr. Deborah Stein, professor of surgery at the University of Maryland School of Medicine.

The study findings were published in The New England Journal of Medicine.