PB1482 - Thrombelastography Identifies Persistent Platelet-mediated Hypercoagulability in Patients with Metastatic Bone Disease Requiring Orthopaedic Surgery

Background: Despite thromboprophylaxis, patients with metastatic bone disease (MBD) are at 7-fold higher risk for venous thromboembolism (VTE) compared to patients without cancer undergoing similar orthopaedic procedures. Limited understanding of the duration of and mechanisms driving post-operative hypercoagulability contribute to this high VTE risk.

Thrombelastography (TEG) is a point-of-care tool that can evaluate hypercoagulability by measuring clot strength (maximal amplitude, MA) in whole blood. Additionally, TEG-based platelet mapping (PLM) analysis can identify platelet hyperactivity via the adenosine diphosphate (ADP) and thromboxane A2 (AA) platelet receptor pathways.

Aims: To assess post-operative hypercoagulability and evaluate the platelet contribution to this hypercoagulable state using serial TEG and PLM analyses.

Methods: Consecutive adults with MBD undergoing orthopaedic surgery for pathologic fracture treatment were enrolled into this single-centre, prospective cohort study (HREBA.CC-20-0147). After obtaining informed consent, serial blood samples for TEG and PLM analyses were collected over a 3-month post-operative period at seven timepoints determined a priori. Patients underwent Doppler ultrasonography on post-operative day (POD) three to screen for proximal DVT. Patients most commonly received low-molecular-weight heparin thromboprophylaxis for four weeks. One-sample t-tests were performed to compare MA values with previously established TEG and PLM thresholds defining hypercoagulability (≥65 mm) and platelet hyperactivity (≥55 mm), respectively.

Results: Forty patients (67±11 years, 57.5% female) were enrolled, five of whom developed VTE (12.5%). Participants demonstrated persistent, platelet-mediated hypercoagulability which remained significantly elevated six weeks post-operatively (ADP-MA: 62.9±5.7 mm, p=0.001; AA-MA: 60.3±13.4 mm, p=0.04) (Figure 1). Those with deep vein thromboses (DVT) demonstrated significantly elevated platelet-mediated hypercoagulability at the time of diagnosis (Table 1).

Conclusion(s): Patients with MBD exhibited platelet-mediated hypercoagulability following orthopaedic surgery, which persisted after thromboprophylaxis was discontinued. Further investigation into safety and efficacy of extended thromboprophylaxis, and use of antiplatelet agents that target the ADP (e.g., clopidogrel) and AA (e.g., aspirin) receptor pathways is warranted.