Time to Venous Thromboembolism Events Following Total Hip Arthroplasty: A Comparison Between Aspirin and Warfarin.

Background: The attitude and approach of orthopedic community for minimizing venous thromboembolism (VTE) has evolved over the last decade with the trend toward use of aspirin (and mechanical modalities) in lieu of aggressive anticoagulation. The optimal length of VTE prophylaxis following total hip arthroplasty (THA) still remains unknown. This study aimed to determine the timing of VTE in patients who received aspirin compared to warfarin, and determine if 30 days of prophylaxis remain adequate.

Methods: This is a retrospective study of 18,003 patients undergoing primary and revision THA at a single institution between January 2008 and August 2020. During this time, our institution underwent a transition from the use of warfarin to aspirin as the main method for VTE prophylaxis. Symptomatic deep vein thrombosis and pulmonary embolism occurring within 90 days of surgery were identified from medical records and phone call logs. Aspirin and warfarin cohorts were matched to account for demographic and comorbidity differences. Timing of pulmonary embolism was determined based on either the date of diagnostic imaging or patient-provider phone calls confirming diagnosis.

Results: The cohorts included 46 patients in the warfarin group and 46 in the aspirin group. Time to VTE was significantly shorter in the warfarin group compared to aspirin (P = .021) with a median time to VTE of 3 days (interquartile range 2-14) and 10 days (interquartile range 4-19) respectively. Over 90% of the events occurred within 32 or 30 days of surgery in the warfarin and aspirin groups respectively.

Conclusion: Based on the findings, a 30-day aspirin prophylaxis remains appropriate for patients undergoing THA.