Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Randomized Controlled Trial
. 2022 Aug 23;328(8):719-727.
doi: 10.1001/jama.2022.13416.

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

Affiliations
Randomized Controlled Trial

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

CRISTAL Study Group et al. JAMA. .

Abstract

Importance: There remains a lack of randomized trials investigating aspirin monotherapy for symptomatic venous thromboembolism (VTE) prophylaxis following total hip arthroplasty (THA) or total knee arthroplasty (TKA).

Objective: To determine whether aspirin was noninferior to enoxaparin in preventing symptomatic VTE after THA or TKA.

Design, setting, and participants: Cluster-randomized, crossover, registry-nested trial across 31 hospitals in Australia. Clusters were hospitals performing greater than 250 THA or TKA procedures annually. Patients (aged ≥18 years) undergoing hip or knee arthroplasty procedures were enrolled at each hospital. Patients receiving preoperative anticoagulation or who had a medical contraindication to either study drug were excluded. A total of 9711 eligible patients were enrolled (5675 in the aspirin group and 4036 in the enoxaparin group) between April 20, 2019, and December 18, 2020. Final follow-up occurred on August 14, 2021.

Interventions: Hospitals were randomized to administer aspirin (100 mg/d) or enoxaparin (40 mg/d) for 35 days after THA and for 14 days after TKA. Crossover occurred after the patient enrollment target had been met for the first group. All 31 hospitals were initially randomized and 16 crossed over prior to trial cessation.

Main outcomes and measures: The primary outcome was symptomatic VTE within 90 days, including pulmonary embolism and deep venous thrombosis (DVT) (above or below the knee). The noninferiority margin was 1%. Six secondary outcomes are reported, including death and major bleeding within 90 days. Analyses were performed by randomization group.

Results: Enrollment was stopped after an interim analysis determined the stopping rule was met, with 9711 patients (median age, 68 years; 56.8% female) of the prespecified 15 562 enrolled (62%). Of these, 9203 (95%) completed the trial. Within 90 days of surgery, symptomatic VTE occurred in 256 patients, including pulmonary embolism (79 cases), above-knee DVT (18 cases), and below-knee DVT (174 cases). The symptomatic VTE rate in the aspirin group was 3.45% and in the enoxaparin group was 1.82% (estimated difference, 1.97%; 95% CI, 0.54%-3.41%). This failed to meet the criterion for noninferiority for aspirin and was significantly superior for enoxaparin (P = .007). Of 6 secondary outcomes, none were significantly better in the enoxaparin group compared with the aspirin group.

Conclusions and relevance: Among patients undergoing hip or knee arthroplasty for osteoarthritis, aspirin compared with enoxaparin resulted in a significantly higher rate of symptomatic VTE within 90 days, defined as below- or above-knee DVT or pulmonary embolism. These findings may be informed by a cost-effectiveness analysis.

Trial registration: ANZCTR Identifier: ACTRN12618001879257.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest Disclosures: Drs de Steiger and Lewis reported being deputy directors of the AOANJRR, under whose registry nested clinical trials platform this study was performed. Dr McDougall reported consulting for Johnson & Johnson in the field of orthopedic instruments and giving paid teaching presentations for Stryker on total knee replacement. Dr Page reported receipt of institutional education and research support from DePuy Synthes. Dr Walter reported receipt of research support grants and personal consulting fees from DePuy Synthes, receipt of royalties from and holding shares in MatOrtho, holding shares in Navbit, receipt of personal consulting fees from Smith + Nephew, receipt of personal consulting fees from MicroPort, and receipt of research support from Think Surgical; in addition, Dr Walter had a patent issued with Navbit not related to anticoagulation. Dr Wilson reported receipt of personal fees from DePuy Australia. No other disclosures were reported.

Figures

Figure 1.
Figure 1.. Participant Flow in a Trial of Anticoagulation After Hip or Knee Arthroplasty
aA total of 1333 patients declined to have their data collected after enrollment; therefore, group allocation was not recorded. These patients were not included in any analysis and are not included in the tallies represented here. bPatients taking dabigatran, rivaroxaban, apixaban, edoxaban, betrixaban, warfarin, or dual antiplatelet therapy preoperatively were excluded from the primary analysis. cPatients who opted out chose to withdraw after initially consenting and prior to 90-day follow-up. dOne additional patient who died recorded a venous thromboembolic event prior to death and therefore was not considered to be missing an outcome.
Figure 2.
Figure 2.. Subgroup Analyses of the Primary Outcome of Symptomatic Venous Thromboembolism (Deep Venous Thrombosis or Pulmonary Embolism) Within 90 Days
Figure 3.
Figure 3.. Kaplan-Meier Analysis of Time to Venous Thromboembolism (Deep Venous Thrombosis or Pulmonary Embolism) Occurrence by Randomized Group
Shaded areas indicate 95% confidence intervals. Median time to venous thromboembolism in the aspirin group was 7.5 days (IQR, 5-9 days); median time to venous thromboembolism in the enoxaparin group was 12 days (IQR, 7-25 days). aThree patients in the aspirin group who experienced a venous thromboembolism did not have a date of event recorded and are excluded from this analysis.

Comment in

Similar articles

Cited by

References

    1. Sloan M, Premkumar A, Sheth NP. Projected volume of primary total joint arthroplasty in the US, 2014 to 2030. J Bone Joint Surg Am. 2018;100(17):1455-1460. doi:10.2106/JBJS.17.01617 - DOI - PubMed
    1. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780-785. doi:10.2106/00004623-200704000-00012 - DOI - PubMed
    1. An VV, Phan K, Levy YD, Bruce WJ. Aspirin as thromboprophylaxis in hip and knee arthroplasty: a systematic review and meta-analysis. J Arthroplasty. 2016;31(11):2608-2616. doi:10.1016/j.arth.2016.04.004 - DOI - PubMed
    1. 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 - DOI - PubMed
    1. Abdel MP, Meneghini RM, Berry DJ. Current practice trends in primary hip and knee arthroplasties among members of the American Association of Hip and Knee Surgeons: an update during the COVID-19 pandemic. J Arthroplasty. 2021;36(7S):S40-S44. doi:10.1016/j.arth.2021.01.080 - DOI - PubMed

Publication types

MeSH terms