Low-Dose Aspirin Once Daily Is Noninferior for Venous Thromboembolic Prophylaxis After Primary Total Joint Arthroplasty: An Analysis of 8,073 Cases Over 10 Years

BACKGROUND: Venous thromboembolism (VTE) is a well-known complication after primary total joint arthroplasty (TJA). Aspirin is increasingly used for VTE prophylaxis after total hip arthroplasty and total knee arthroplasty given its efficacy and favorable side effect profile, although optimal dosing and frequency remain uncertain. Given the long-term effect of aspirin on platelet function, the conventional twice-daily frequency (or higher dosing) of aspirin may be unnecessary. The purpose of this study was to investigate the VTE incidence in patients receiving 81 mg aspirin once daily for prophylaxis after primary TJA, which has been our institution's protocol for the past decade. METHODS: This was a retrospective study of 8,073 patients who underwent primary THA and TKA from a single institution between 2014 and 2023. Patients who experienced a VTE event within 90 days of surgery were identified using our statewide registry. The VTE rates were compared between patients receiving aspirin 81 mg once daily, a higher dose/frequency of aspirin, or more potent anticoagulation. Univariate and logistic regression analyses were performed. RESULTS: The overall VTE rate was 1.1% (90 of 8,073), with a lower incidence after total hip arthroplasty compared to total knee arthroplasty (0.9 versus 1.4%, respectively, P = 0.02). In our logistic regression analyses, there was no difference in VTE rate between all anticoagulation methods (P = 0.61). The only variable that was predictive of VTE was a higher Elixhauser Comorbidity Index (odds ratio 1.09, 95% confidence interval 1.04 to 1.15, P < 0.01). CONCLUSIONS: Our institutional protocol of using 81 mg aspirin once daily has an acceptable incidence rate of VTE after TJA. It is noninferior to the conventional twice-daily 81 mg aspirin or higher dosing, as well as potent anticoagulants.