Recent study results suggest that aspirin may be an effective alternative to the use of low-molecular-weight heparin (LMWH) to prevent clots in patients who have had fractures. Yet, evidence from head-to-head comparisons in patients who've been treated operatively for fractures is lacking. What is known is that patients favor aspirin over LMWH because of lower costs and more convenient administration.

A pragmatic, randomized trial conducted at 21 trauma centers was undertaken to determine whether aspirin was noninferior to LMWH regarding thromboembolic outcomes in people who had orthopedic trauma. A total of 12,211 patients (mean age, 44.6 years; 62.3%, men) were randomly assigned to aspirin (81 mg twice daily) or LMWH (enoxaparin 30 mg twice daily) for clot prevention. Patients were ages 18 years or older and had an extremity fracture that was treated operatively or a fracture of the pelvis or acetabulum that was treated operatively or nonoperatively. Thromboprophylaxis could end at discharge or be continued according to the clinical protocols of each hospital. The mean number of inpatient doses of a trial medication was 8.6+/-10.8 in the aspirin group and 9.1+/-10.5 in the group receiving LMWH; at discharge, 91% of patients had been receiving thromboprophylaxis for a median of 21 days.

During 90 days of follow-up, 47 of 6,101 patients (0.78%) in the aspirin group and 45 of 6,110 patients (0.73%) in the LMWH group died, indicating aspirin was noninferior but not superior to LMWH for the prevention of death from any cause. Nonfatal pulmonary embolism occurred in 90 patients (1.49%) in each group. Deep vein thrombosis occurred in 151 patients (2.51%) and 103 patients (1.71%) in the aspirin and LMWH groups, respectively. The incidence of bleeding events, wound complications, and deep surgical site infections was similar in both groups.

One limitation of the study was that some patients received up to two doses of LMWH before enrollment. Another was that the duration of thromboprophylaxis after discharge wasn't mandated, which may have influenced outcomes. In addition, the researchers note that the trial was open label, and the primary outcome was changed after enrollment began from death related to pulmonary embolism to death from any cause.