Comparable Efficacy of 100 mg Aspirin Twice Daily and Rivaroxaban for Venous Thromboembolism Prophylaxis Following Primary Total Hip Arthroplasty: A Randomized Controlled Trial
Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), is a well-established complication associated with total hip arthroplasty (THA). Post-operative VTE results in significant patient morbidity and mortality, as well as a substantial financial burden due to costly medical management and prolonged hospital stays. As the number of THA procedures continues to increase globally, the need for safe and effective VTE prophylaxis becomes paramount. While prophylactic antithrombotic therapy has been shown to reduce post-operative VTE risk, the ideal drug regimen that balances antithrombotic efficacy with bleeding risk remains controversial.
Currently, the mainstay of VTE chemoprophylaxis includes low-molecular-weight heparin (LMWH) and new oral anticoagulants (NOACs), such as rivaroxaban. Rivaroxaban has demonstrated superior safety, thromboprophylaxis efficacy, and convenience compared to LMWH, making it a commonly prescribed option following joint arthroplasty. However, rivaroxaban is associated with a higher risk of bleeding and incisional complications. Aspirin, an antiplatelet agent, has been proposed as an alternative for VTE prophylaxis. It is inexpensive, orally administered, and requires minimal blood monitoring. Despite its widespread use, the optimal dose of aspirin for VTE prophylaxis following THA remains unclear, with varying regimens reported in the literature.
This study aimed to evaluate and compare the safety and efficacy of 100 mg aspirin administered twice daily with rivaroxaban (10 mg once daily) for VTE prophylaxis following elective primary unilateral THA. The hypothesis was that 100 mg aspirin twice daily would be comparable to rivaroxaban in preventing VTE, with similar peri-operative blood loss and bleeding risk.
Methods
This randomized controlled trial (RCT) was conducted in compliance with the Declaration of Helsinki and approved by the local Institutional Review Board. Patients undergoing elective unilateral primary THA between January 2019 and January 2020 were prospectively enrolled and randomly allocated to receive either oral enteric-coated aspirin (100 mg twice daily) or rivaroxaban (10 mg once daily) for 5 weeks of VTE prophylaxis. The study included patients aged 20 to 80 years who had ceased aspirin use for at least one week before surgery. Patients with a high risk of VTE, such as those with a history of VTE, active malignancy, or prothrombotic conditions, were excluded.
All surgeries were performed using the posterior-lateral approach under general anesthesia by two experienced orthopedic surgeons. Tranexamic acid was administered intravenously before incision and topically before wound closure. Post-operatively, patients received pneumatic compression during their hospital stay and began crutch-assisted partial weight-bearing ambulation on post-operative day 1 (POD 1). Follow-up assessments were conducted at PODs 30 and 90.
Primary outcomes included the incidence of symptomatic VTE, DVT diagnosed via Doppler ultrasonography, total blood loss (TBL), and bleeding events. Secondary outcomes included Harris Hip Score (HHS), post-operative recovery, and the incidence of other complications such as gastrointestinal (GI) adverse events and wound complications.
Results
A total of 70 patients were included in the study, with 34 in the aspirin group and 36 in the rivaroxaban group. No cases of symptomatic VTE occurred in either group. The DVT rate on Doppler ultrasonography was similar between the aspirin and rivaroxaban groups (8.8% vs. 8.3%, respectively), confirming the non-inferiority of aspirin for DVT prophylaxis. The calculated TBL in the aspirin group (944.9 mL) was comparable to that in the rivaroxaban group (978.3 mL). There were no significant differences in HHS at POD 30 or POD 90, the incidence of bleeding events (2.9% vs. 8.3%), or GI complications (2.9% vs. 5.6%) between the two groups.
Univariable analysis identified non-idiopathic etiological factors and elevated D-dimer levels on POD 1 as significant risk factors for DVT. Multivariable logistic regression confirmed that the choice of aspirin or rivaroxaban was not significantly associated with DVT occurrence after adjusting for these factors.
Discussion
The findings of this study support the use of 100 mg aspirin twice daily as a safe and effective option for VTE prophylaxis following primary THA. The DVT rate in the aspirin group was comparable to that in the rivaroxaban group, and there were no significant differences in bleeding events or GI complications. These results align with previous studies that have demonstrated the efficacy of aspirin in preventing VTE, particularly at lower doses.
Aspirin’s mechanism of action involves inhibiting platelet aggregation, which is crucial for preventing venous thrombosis. While higher doses of aspirin have been associated with increased GI side effects, the 100 mg twice daily regimen used in this study appeared to balance efficacy with safety. The absence of major bleeding events in both groups further supports the use of aspirin as a viable alternative to rivaroxaban.
The study also highlighted the importance of early mobilization and the use of pneumatic compression devices in reducing VTE risk. These measures, combined with chemoprophylaxis, contribute to the overall low incidence of VTE observed in this study.
Limitations
This study has several limitations. First, it was a single-center study with a relatively small sample size, which may limit the generalizability of the findings. Second, the study was not powered to detect superiority between the two treatment groups but rather to establish non-inferiority. Third, Doppler ultrasonography was performed between PODs 14 and 30, potentially missing thrombotic events that occurred later. Finally, the study excluded patients with cardiovascular risk, limiting the ability to assess the co-effect of aspirin in preventing arterial thrombotic events.
Conclusion
In conclusion, this study demonstrated that 100 mg aspirin twice daily is non-inferior to rivaroxaban for VTE prophylaxis following primary THA. Aspirin use resulted in similar rates of DVT, bleeding events, and GI complications compared to rivaroxaban. These findings support the use of aspirin as a cost-effective and widely available option for VTE prophylaxis in THA patients. Future multicenter studies with larger sample sizes are warranted to further validate these results and explore the use of aspirin in different patient populations.
doi.org/10.1097/CM9.0000000000001305
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