Charles Marc Samama

This is the first large randomized study comparing aspirin and enoxaparin after total hip or knee replacement, and the authors have to be commended for this. Non-inferiority is not reached by aspirin. Enoxaparin is more effective with no difference in major bleeding, but this study is a cluster-randomized, crossover, registry-nested trial across 31 hospitals in Australia and clusters were in hospitals performing greater than 250 total hip arthroplasty (THA) or total knee arthroplasty (TKA) procedures annually. 5,675 patients were enrolled in the aspirin group and 4,036 in the enoxaparin group. Are the groups comparable? There were different numbers from different hospitals. Further, there were other limitations of the study: 1. The study was not focused on fast-track and ambulatory patients who may better benefit from aspirin 2. There was no confirmation of symptomatic events 3. The study stopped after an interim analysis leading to a lack of power 4. Overweight patients: mean BMI around 30 5. 15% of enoxaparin patients were also treated with aspirin and received both treatments 6. There was no difference in proximal thromboses and pulmonary embolisms. 7. There are many more distal thromboses in the aspirin group, but do we care? In summary, probably the largest randomized study focussing on this controversial issue. It will be cited many times in the future, but it doesn't close the controversy. To be read completely and kept in mind. Trial registration details: ACTRN12618001879257