Preventing blood clots after major joint surgery remains a top priority for orthopaedic surgeons. Therefore, choosing the safest and most effective protocol for postoperative thromboprophylaxis is crucial for patient recovery. Traditionally, clinical guidelines recommended direct oral anticoagulants like rivaroxaban before transitioning to aspirin. However, new clinical trial evidence suggests we can safely simplify this postoperative regimen.
The Clinical Dilemma of Postoperative Thromboprophylaxis
Patients face a high risk of developing deep-vein thrombosis or pulmonary embolism after undergoing total hip or knee replacement. To address this risk, doctors regularly prescribe blood thinners immediately after surgery. Consequently, clinical practice often involves direct oral anticoagulants, which carry a higher cost and a potential risk of bleeding. In contrast, aspirin offers an affordable and highly accessible alternative. Nevertheless, medical researchers long debated whether aspirin alone could provide sufficient protection without an initial direct oral anticoagulant course.
How the EPCAT III Trial Evaluated Aspirin Efficacy
To settle this debate, the landmark multicenter EPCAT III trial evaluated aspirin alone against a hybrid regimen. Specifically, the double-blind, randomized, controlled trial enrolled 5,429 patients who underwent total hip or knee arthroplasty. Clinicians randomly assigned patients to receive either 81 mg of aspirin or 10 mg of oral rivaroxaban for five days. Subsequently, all patients received 81 mg of aspirin daily for additional days based on their surgery. Specifically, knee arthroplasty patients took aspirin for 9 more days, while hip arthroplasty patients took it for 30 more days.
Efficacy and Safety Outcomes from the Trial
Ultimately, the trial demonstrated that aspirin alone is noninferior to the hybrid rivaroxaban-aspirin course. For instance, symptomatic venous thromboembolism developed in 13 of 2,718 patients (0.48%) taking aspirin alone. Similarly, 12 of 2,647 patients (0.45%) in the rivaroxaban-aspirin group developed venous thromboembolism. This represents an extremely small risk difference of 0.02 percentage points. Furthermore, the two groups showed similar rates of major or clinically relevant bleeding complications. Therefore, the researchers successfully established the safety of immediate postoperative aspirin therapy.
Frequently Asked Questions
Q1: Is aspirin alone effective for preventing blood clots after joint replacement surgery?
Yes. The EPCAT III trial proved that immediate aspirin therapy matches the safety of a hybrid regimen. Additionally, both strategies showed extremely low rates of venous thromboembolism.
Q2: Does using aspirin alone increase the risk of bleeding compared to rivaroxaban?
No. Actually, the trial demonstrated that both regimens have similar safety profiles. Moreover, patients in both groups experienced comparable rates of major and clinically relevant bleeding complications.
References
- Shivakumar S et al. Rivaroxaban Then Aspirin vs. Aspirin Alone after Total Hip or Knee Arthroplasty. N Engl J Med. 2026 Jul 12. doi: 10.1056/NEJMoa2603649. PMID: 42437501.
- Marc Carrier: EPCAT III Trial at ISTH 2026 Supports Aspirin Alone for VTE Prevention After Arthroplasty. Hemostasis Today. 2026 Jul 12.