CRISTAL

Effect of Aspirin vs Enoxaparin on Symptomatic Venous Thromboembolism in Patients Undergoing Hip or Knee Arthroplasty: The CRISTAL Randomized Trial.

Sidhu VS, Kelly TL, Pratt N, et al. JAMA 2022 · PMID 35997730 · doi:10.1001/jama.2022.13416

Question

Is aspirin non-inferior to enoxaparin for preventing symptomatic VTE after hip or knee replacement?

Design

Registry-nested, cluster-randomised crossover non-inferiority trial in 31 Australian hospitals.

Patients

Adults undergoing hip or knee arthroplasty at high-volume Australian hospitals, excluding those already anticoagulated or with contraindications to either drug.

Intervention

Aspirin 100 mg daily (35 days after THA, 14 days after TKA)

Comparison

Enoxaparin 40 mg daily for the same durations

Primary outcome

Symptomatic VTE within 90 days

Key result

Aspirin failed to show non-inferiority and was associated with a significantly higher rate of symptomatic VTE than enoxaparin, mainly driven by below-knee DVT. There was no significant difference in death or major bleeding.

Limitations

Cluster design with open-label treatment, and the excess was mostly distal DVT of uncertain clinical importance; the trial was stopped early.

Impact on practice

Challenges the use of aspirin alone after arthroplasty and supports LMWH-based regimens in line with NICE NG89.