PROLONGED PLATELET-MEDIATED HYPERCOAGULABILITY EXISTS FOLLOWING PRIMARY TOTAL HIP AND KNEE ARTHROPLASTY

Total hip and knee arthroplasty (THA, TKA) are effective treatments for osteoarthritis. However, these surgeries increase risk for venous thromboembolism (VTE). Clinical practice guidelines recommend thromboprophylaxis for 10-35 post-operative days, however, the duration of increased VTE risk is unknown. Platelets play a crucial role in clot formation through various pathways. Acetylsalicylic acid (ASA) is an anti-platelet agent that targets the arachidonic acid (AA) pathway and continues to be studied for optimal use in preventing VTE following THA and TKA. Thrombelastography (TEG) is a point-of-care tool that assesses individual coagulation profiles, where the maximal amplitude parameter (MA, a measure of clot strength) has been used to define hypercoagulability and identify patients at risk for VTE (Gary et al. 2016). The TEG-based Platelet Mapping (PLM) analysis can assess platelet function with anti-platelet use, and the AA-MA parameter is a measure of the platelet contribution to clot strength. This study aimed to quantify the duration and platelet contribution to hypercoagulability, and the efficacy of platelet inhibition in ASA-treated patients, following THA and TKA. This prospective cohort study enrolled patients aged 50 or older who underwent a primary THA or TKA, excluding those with a history of VTE, therapeutic anticoagulant use, bleeding disorders, active malignancies, or rheumatoid arthritis. Serial whole blood samples were collected pre-operatively and post-operatively until 12-weeks, and analyzed using a TEG6s hemostasis analyzer (Haemonetics Corporation, Braintree MA). Hypercoagulability was defined as a MA ≥ 65mm, and platelet hyperactivity was defined as an AA-MA ≥ 55mm. Thromboprophylaxis was standardized to ASA 81mg daily for 28 days following THA and for 14 days following TKA. One-sample t-tests were used to compare mean MA and AA-MA values at each timepoint to the respective threshold. Seventy patients (36 THA, 34 TKA; 40 (57%) female), with a mean age of 68 (SD=8.8) years were included. At the thromboprophylaxis completion timepoint, 73% of THA patients (MA=66.1 [SD=3.3], p = 0.12) and 100% of TKA patients (MA=69.7 [SD=4.3], p This study demonstrated persistent platelet-mediated hypercoagulability and platelet hyperactivity in most patients following THA and TKA, beyond the duration of thromboprophylaxis. Additionally, those who suffered VTE complications displayed significantly elevated MA values, indicating the potential for TEG to identify at-risk patients, emphasizing the need for further research. Lastly, PLM analysis was able to serially quantify platelet inhibition with the use of anti-platelet thromboprophylaxis.