A Narrative Review of Aspirin Resistance in VTE Prophylaxis for Orthopaedic Surgery.

Total hip arthroplasties (THA) and total knee arthroplasties (TKA) confer one of the highest risks for developing venous thromboembolism (VTE) and pharmacological prophylaxis is imperative to help mitigate the risks. Aspirin is the most cost-effective medication for VTE prophylaxis, and its use post-THA/TKA has grown in popularity. Aspirin resistance is categorised as clinical or laboratory resistance with obesity, advancing age, diabetes mellitus, dyslipidaemia and inflammatory diseases identified as risk factors for aspirin resistance. Treatment failure due to aspirin resistance has been reported in cardiovascular and cerebrovascular disease leading to increased rates of mortality and re-embolisation. However, aspirin resistance in patients undergoing a THA/TKA has not been described, nor has there been investigation into the incidence rates or clinical outcomes. The aim of this narrative review is to appraise the concept of aspirin resistance in the context of aspirin use for VTE prophylaxis after THA/TKA surgeries. This is important to investigate as the risk factors for aspirin resistance, including obesity, advancing age, diabetes mellitus, dyslipidaemia and inflammatory diseases, are also risk factors for THA/TKA and risk factors for VTE. The presence of aspirin resistance in patients undergoing orthopaedic surgery may place patients at greater risk of thrombotic events if aspirin is prescribed for VTE prophylaxis. This could further increase the risk of complications associated with VTE and potential long-term consequences such as post-thrombotic syndrome. Future research is required to explore and quantify the rates of aspirin resistance and the clinical outcomes in orthopaedic patients; especially in those patients with these overlapping risk factors for THA/TKA, VTE and aspirin resistance.