Aspirin for prevention of venous thromboembolism in recipients of major lower-limb orthopaedic surgery: a systematic review of level I evidence.

INTRODUCTION: Major lower-limb orthopaedic surgery recipients are at increased risk of venous thromboembolism (VTE). The optimal strategy for preventing VTE is a topic of ongoing debate. The use of aspirin has been implicated in reducing VTE events and is potentially advantageous compared to other agents in respect to cost, access, route of administration and reduced adverse effects such as bleeding. EVIDENCE ACQUISITION: A systematic search for Level I evidence (systematic reviews and meta-analyses of randomised- controlled trials) was performed in April 2019 to evaluate the use of aspirin for primary and secondary VTE prophylaxis compared to alternative chemical and mechanical strategies. This search encompassed three electronic databases (Pubmed, Embase and the Cochrane Database of Systematic Reviews). All references of included studies were screened for additional studies. Data was compiled and compared to the recommendations and guidelines published by major institutions. Included studies were appraised with the aid of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. EVIDENCE SYNTHESIS: In total, 22 studies were included. Interventions and outcomes identified were heterogeneous across studies. Most statistical tests applied found no difference between aspirin and other interventions in regards to deep vein thrombosis, pulmonary embolism, bleeding and mortality outcomes. CONCLUSIONS: Aspirin may be a viable alternative to established thromboprophylactic regimes for primary prevention of VTE, however in the setting of secondary prevention it is generally less efficacious.Future studies should have clearly identified and comparable outcome measures, with direct comparisons and assessment of intervention combination, dosing and treatment duration.