Is Aspirin Safe and Effective After Joint Arthroplasty?

Venous thromboembolism remains a dreaded complication following major lower extremity joint replacement surgery. Consequently, orthopedic surgeons frequently prescribe aspirin for VTE prophylaxis due to its low cost, oral convenience, and minimal bleeding risk. However, conflicting trial data have fueled an enduring clinical debate regarding whether aspirin matches potent anticoagulants in efficacy. The landmark PEPPER pragmatic clinical trial directly addresses this controversy by comparing aspirin against warfarin and rivaroxaban.

Trial Design and Regimens

The multicenter, noninferiority PEPPER trial evaluated patients undergoing elective primary or revision total hip or knee arthroplasty. Specifically, investigators randomly assigned 18,883 adult participants to one of three oral regimens for 30 days. Patients received enteric-coated aspirin at 81 mg twice daily, adjusted-dose warfarin, or rivaroxaban at 10 mg daily. In addition, all participants used mechanical pneumatic compression during inpatient stays. Blinded evaluators subsequently tracked clinical events through six months across 15,317 patients in the per-protocol cohort. Furthermore, the researchers defined a strict noninferiority margin of 0.69 percentage points for risk differences.

Efficacy Outcomes of Aspirin for VTE Prophylaxis

The primary effectiveness outcome assessed a composite of all-cause death or symptomatic venous thromboembolism. At six months, primary events occurred in 1.26% of aspirin patients, 1.23% of warfarin patients, and 0.94% of rivaroxaban recipients. Pairwise analyses demonstrated an absolute risk difference of 0.30 percentage points between aspirin and rivaroxaban. However, the upper boundary of the confidence interval reached 0.81 percentage points. Because this boundary exceeded the predefined 0.69 threshold, aspirin failed to establish statistical noninferiority. Similarly, aspirin was not noninferior to warfarin, which also yielded an upper confidence bound of 0.81. In contrast, warfarin successfully met the noninferiority standard when investigators compared it to rivaroxaban.

Safety Profiles and Bleeding Complications

Safety outcomes included major bleeding, reoperation for wound healing complications, or acute myocardial infarction. Notably, aspirin demonstrated superior safety over both anticoagulant therapies. Primary safety events occurred in 2.91% of aspirin recipients, compared to 3.36% for warfarin and 3.48% for rivaroxaban. The absolute risk difference was 0.68 percentage points between rivaroxaban and aspirin. Meanwhile, the safety difference between warfarin and aspirin reached 0.77 percentage points. Neither rivaroxaban nor warfarin proved noninferior to aspirin regarding safety. Therefore, the lower thrombotic risk with anticoagulants came at the direct expense of increased bleeding complications. Consequently, surgeons must carefully balance bleeding risks against clot prevention in individual patients.

Clinical Implications for Practice

These landmark findings offer crucial guidance for surgical teams managing arthroplasty patients. Although rivaroxaban provided the lowest overall rate of venous thromboembolism, it significantly increased bleeding risks. Conversely, aspirin minimized wound reoperations and bleeding events, but it allowed slightly more thromboembolic events. In Indian clinical practice, orthopedic surgeons must weigh patient-specific factors before selecting a chemoprophylactic agent. For instance, high-risk patients with previous thromboembolism or obesity may benefit more from potent anticoagulation with rivaroxaban. In contrast, standard-risk patients prone to hematoma or wound breakdown may achieve better net outcomes with aspirin. Thus, personalized risk stratification should replace universal one-size-fits-all prophylaxis protocols.

Frequently Asked Questions

Q1: Did the PEPPER trial demonstrate that aspirin was noninferior to rivaroxaban?

No. Aspirin failed to meet the statistical noninferiority margin of 0.69 percentage points when compared to rivaroxaban. However, the absolute difference in symptomatic thromboembolism between the two treatments remained small at 0.30 percentage points.

Q2: How did the bleeding safety profile of aspirin compare to direct oral anticoagulants?

Aspirin showed a significantly lower rate of primary safety complications than rivaroxaban or warfarin. Specifically, safety events occurred in 2.91% of aspirin patients compared to 3.48% of rivaroxaban patients. Consequently, anticoagulants failed to demonstrate noninferiority for safety.

Q3: What do these trial results mean for post-arthroplasty patient care?

The findings emphasize the importance of personalized thromboprophylaxis after total hip or knee arthroplasty. Therefore, clinicians should reserve anticoagulants for high-thrombosis-risk patients, while selecting aspirin for patients vulnerable to bleeding.

References

1. Pellegrini VD et al. Prevention of Venous Thromboembolism after Total Hip or Knee Replacement. N Engl J Med. 2026 Nov 12. doi: 10.1056/NEJMoa2602435. PMID: 43013818.
2. Anderson DR, Dunbar M, Murnaghan J, et al. Aspirin or Rivaroxaban for VTE Prophylaxis after Hip or Knee Arthroplasty. N Engl J Med. 2018;378(8):699-707. doi:10.1056/NEJMoa1712746.
3. Mont MA, Jacobs JJ. AAOS clinical practice guideline: preventing venous thromboembolic disease in patients undergoing elective hip and knee arthroplasty. J Am Acad Orthop Surg. 2011;19(12):777-778.