PROLONGED PLATELET-MEDIATED HYPERCOAGULABILITY OCCURS FOLLOWING SURGICALLY TREATED HIP FRACTURES AND ASA REDUCES PLATELET HYPERACTIVITY

Hip fractures are an epidemic and despite thromboprophylaxis, venous thromboembolism (VTE) rates remain high (2.5–5%). Serial thrombelastography (TEG) analysis can quantify hypercoagulable state and increased VTE risk. Injury, surgery, and immobility result in a prolonged hypercoagulable state beyond current thromboprophylaxis guidelines with 46% of VTE occurring 6 weeks after surgery or later. TEG-based platelet mapping (PLM) can activate platelets at the adenosine diphosphate (ADP) receptor or the thromboxane A2 (AA) receptor, to evaluate clot strength when platelets are activated through those specific receptors. This study aimed to evaluate platelet contribution to hypercoagulability and to evaluate the effect of acetylsalicylic acid (ASA) following hip fracture surgery. Consecutive adult patients undergoing acute hip fracture surgery were enrolled in this prospective cohort study. Exclusion criteria were prior VTE, active malignancy, or pre-injury therapeutic anticoagulation. Following informed or surrogate consent, serial TEG and PLM analysis was performed at admission, post-operative day (POD) 1, 3, 5, 7 and at 2-, 4-, 6-, and 12-weeks post-operatively, using the TEG6s hemostasis analyzer (Haemonetics Corporation). All patients received thromboprophylaxis for 28 days post-operatively. Hypercoagulability was defined as maximal amplitude (MA; a measure of clot strength) over 65 mm. Platelet hyperactivity was defined as MA via the ADP or AA pathway over 55 mm. T-tests were used to compare MA values with the hyperactivity threshold and between those receiving ASA or not. One-sample t-test used for MA compared with the threshold values at each timepoint. Two sample t-tests at each timepoint and chi-square analyses for demographics were used to compare between those on ASA and those not. A total of 101 patients were enrolled with a mean age of 77.3 (± 11.5) years and 65% being female. Eighteen patients (17.9%) received ASA post-operatively, while the rest received low molecular weight heparin (LMWH). There was no statistically significant difference in age (p = 0.9), sex (p = 0.2), or surgical treatment type (p = 1.0) between those receiving ASA and those who were not. TEG analysis demonstrated prolonged hypercoagulability (MA > 65mm) for over 50% of patients at four weeks post-operatively, when thromboprophylaxis is discontinued. PLM analysis identified prolonged platelet-mediated hypercoagulability based on elevated ADP-MA and AA-MA, with more pronounced platelet contribution via the AA pathway. Patients who received ASA post-operatively demonstrated reduced platelet hyperactivity, with statistically significant reduction on POD 5 and POD 7 (p This study confirmed prolonged hypercoagulability and increased VTE risk beyond four weeks for over 50% of patients undergoing hip fracture surgery based on serial TEG analysis. Additionally, TEG-based PLM analysis identified prolonged platelet-mediated hypercoagulability, with more pronounced platelet contribution via the AA pathway. PLM analysis also demonstrated that ASA thromboprophylaxis can significantly reduce platelet hyperactivity. This study supports further investigation into the safety and efficacy of prolonged thromboprophylaxis for some patients and the investigation of antiplatelet thromboprophylaxis, such as ASA, following hip fracture surgery.