An Early Coagulation Factor Dominant Hypercoagulability Is Followed by a Prolonged Platelet-Dominant Hypercoagulability in Patients Requiring Hip Fracture Surgery

Purpose: The risk for venous thromboembolism (VTE) after hip fracture surgery (HFS) remains high. A subanalysis of the FAITH and HEALTH trials demonstrated a 2.5% VTE rate, with 45.3% of VTE events occurring more than 6 weeks post-fracture, beyond currently recommended thromboprophylaxis. Thrombelastography (TEG) is a whole-blood assay that provides a comprehensive analysis of hemostasis from clot initiation to fibrinolysis. This study used serial TEG analysis to determine the different phases of coagulation responsible for hypercoagulability after HFS.

Methods: In this single-center prospective cohort study, consecutive patients requiring HFS underwent serial TEG analysis until 12-week follow-up. Hypercoagulability was defined by TEG parameter values beyond the reference range for clot initiation (Activated Clotting Time [ACT], Reaction-time [R-time]) and clot propagation (Kinetic-time [K-time] and Alpha-angle). A hypercoagulable threshold of >65 mm was used for Maximal Amplitude (MA), a measure of platelet contribution to maximal clot strength. Paired sample t-tests were used to compare admission values to time points when TEG parameters were beyond reference ranges. One-sample t-tests were used to compare MA values and the hypercoagulability threshold at each time point.

Results: In total, 251 patients were included with a median age of 79 years (interquartile range [IQR] 71-87) and with 66% being female. There were 6 symptomatic VTE events (2.4%), where significantly elevated MA occurred on postoperative day (POD)5 (mean MA = 70.7, standard deviation [SD] = 1.5; P<0.001) and at 2 weeks (mean MA = 76.1, SD = 4.2; P<0.001). In the overall cohort, ACT and R-time demonstrated shorter time to clot initiation until 2-week follow-up (ACT mean difference = 6.7 sec, 95% confidence interval [CI], 3.79-9.66; P<0.0001 and R-time mean difference = 0.07 min, 95% CI, 0.04-0.1; P<0.0001), signifying early increased coagulation factor-dominant hypercoagulability. MA values (clot strength) peaked at 2 weeks (mean MA difference = 8.87, 95% CI, 7.90-9.84; P<0.0001), as well as Alpha-angle (rate of clot formation; mean difference = 5.75, 95% CI, 5.15-6.35; P<0.0001). A total of 86% of patients had persistently elevated MA at 4 weeks (mean = 67.5, SD = 3.5; P<0.0001) and 72% remained hypercoagulable at 6 weeks (mean = 65.7, SD = 4.6; P = 0.021), supporting prolonged platelet-predominant hypercoagulability.

Conclusion: TEG analysis demonstrated early hypercoagulability after HFS related to increased procoagulant factor activity, supporting early thromboprophylaxis with anticoagulants that target procoagulant factors (oral anticoagulants or low molecular-weight heparin). Prolonged platelet-dominant hypercoagulability extended beyond currently recommended thromboprophylaxis, suggesting that extended antiplatelet thromboprophylaxis may be beneficial. Future studies targeting procoagulant factors and platelet hyperactivity may help prevent VTE after HFS.

Graphic