ThromboPROphylaxisHIP Fracture Oral thromboPROphylaxis (Hip PRO Pilot)

Inclusion Criteria:

Patients aged 50 years or older with an acute hip fracture (presentation to hospital within 24 hours of injury) that requires surgical treatment will be approached for inclusion in the study:

1. Age ≥ 50 years with a hip fracture (AO-OTA classification 31-A1-A3 and 31-B1-B3) amenable to surgical treatment (presentation to hospital within 24 hours of injury). Patients with additional injuries will be included and any additional injuries will be documented.
2. Both open and closed fractures will be included, and open fractures will be documented.
3. Patients on single agent anti-platelet therapy (i.e., acetylsalicylic acid or clopidogrel) will be included.
4. Signed informed consent or surrogate consent to participate in study.

Exclusion Criteria:

1. Delayed presentation (over 24 hours between hip fracture and presentation to hospital).
2. Pathological fractures secondary to primary cancer or metastatic bone disease.
3. Peri-prosthetic femur fractures.
4. Received more than two doses of any thromboprophylaxis agent post-operatively, prior to randomization.
5. Pre-hospital therapeutic intensity antithrombotic therapy, including LMWH, Warfarin, DOACs, clopidogrel/ticagrelor, or chronic ASA use of any dose in the three months prior to hip fracture.
6. Known inherited bleeding or clotting disorder (factor V Leiden gene mutation, prothrombin gene mutation, protein C or protein S deficiency, antithrombin deficiency).
7. Intracranial hemorrhage requiring serial CT scans of the brain and/or surgical intervention.
8. Contraindication to ASA use (allergy, documented gastrointestinal ulcer within the past year, severe thrombocytopenia \[platelet count <50 x109/L at the time of hospital admission\]).
9. Contraindication to rivaroxaban use (allergy, acute renal failure \[CrCl <30 mL/min\]).
10. Participant or surrogate unable to or unwilling to provide consent or complete follow-up. Or surrogate consent not available.
11. Under age 50 years (more likely high energy, multiple injuries).
12. Multiply injured patients who require prolonged thromboprophylaxis or delayed thromboprophylaxis initiation.
13. Patient unable to attend follow-up visits.
14. Currently incarcerated, at a correctional facility.