HIP Fracture Oral ThromboPROphylaxis (Hip PRO Pilot)

• Background:

With over 30,000 hip fractures in Canada annually, these injuries are an epidemic. Venous thromboembolism (VTE) events are common following hip fracture surgery (HFS) and include life-threatening pulmonary embolism (PE; a leading cause of preventable mortality) and debilitating deep vein thromboses (DVTs; second most common complication). Thromboprophylaxis reduces VTE, but the optimal medication remains unknown.

Low molecular weight heparin (LMWH) has been the mainstay, but adherence is poor: only 1 in 5 patients adhere after HFS, limiting its effectiveness. Meta-analyses support that direct oral anticoagulants (DOACs) are as effective as LMWH in prevention of VTE, but the data are limited by borderline effect sizes, small sample sizes, and inconsistent outcomes. Our survey found that surgeons report safety concerns and are reluctant to use DOACs due to post-operative bleeding risk.

Our research demonstrates platelet-dominant hypercoagulability using serial thrombelastography (TEG), reduced platelet activity with aspirin (ASA) use, and maybe increasing comfort with prescribing ASA post-HFS. Randomized controlled trials (RCTs) comparing LMWH and ASA post-injury are limited by non-standardized therapy duration, asymptomatic DVT inclusion, and patient heterogeneity. ASA has been favourably compared to DOACs and LMWH in arthroplasty RCTs examining oral thromboprophylaxis following total hip and total knee arthroplasty. Continued morbidity and mortality, patient and surgeon preference, and our network meta-analysis support the need for comparison between DOAC and ASA for VTE prevention after HFS. Based on our research, our resent network meta-analysis supporting oral thromboprophylaxis, along with patient preference for oral medications, there is a need for comparison between DOAC and ASA for prevention of VTE to reduce the continued morbidity and mortality that ensues following HFS.

• Objectives:

Specific Aims:

• Feasibility: This pilot trial will evaluate the feasibility of a full-scale RCT comparing the safety and efficacy of rivaroxaban versus ASA for thromboprophylaxis after HFS, based on achieving recruitment targets, study drug adherence, and participant retention.
• Safety and Efficacy: Key clinical data will be collected to estimate VTE and bleeding complications to inform the full-scale RCT.

(3) Methods:

This is a multi-centre double-blind pilot trial consisting of consecutive eligible patients 50 years or older requiring HFS who will be randomized (1:1) via web-based randomization to rivaroxaban 10 mg daily for 35 days or ASA 81 mg daily for 35 days, with 90-day follow-up. The primary feasibility outcome measure is an estimate of the mean monthly recruitment rate over 12 months across participating sites, including 95% confidence intervals, with a priori feasibility criteria determining progression to the full trial. Secondary feasibility outcomes are consent and retention rates, and drug adherence.

Secondary clinical outcomes will include symptomatic VTE, major bleeding, clinically relevant non-major bleeding, and 90-day mortality (independently and blindly adjudicated). Intention-to-treat analysis will be used, and subgroup analysis will compare age, sex, gender, and surgical type. Additional patient-reported (the Cumulated Ambulation Score and Clinical Frailty Scale), value-based (direct and indirect costs) and translational (coagulation) outcomes will be included.

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:

• 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.
• Both open and closed fractures will be included, and open fractures will be documented.
• Patients on single agent anti-platelet therapy (i.e., acetylsalicylic acid or clopidogrel) will be included.
• Signed informed consent or surrogate consent to participate in study.

Exclusion criteria

• Delayed presentation (over 24 hours between hip fracture and presentation to hospital).
• Pathological fractures secondary to primary cancer or metastatic bone disease.
• Peri-prosthetic femur fractures.
• Received more than two doses of any thromboprophylaxis agent post-operatively, prior to randomization.
• 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.
• Known inherited bleeding or clotting disorder (factor V Leiden gene mutation, prothrombin gene mutation, protein C or protein S deficiency, antithrombin deficiency).
• Intracranial hemorrhage requiring serial CT scans of the brain and/or surgical intervention.
• 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]).
• Contraindication to rivaroxaban use (allergy, acute renal failure [CrCl <30 mL/min]).
• Participant or surrogate unable to or unwilling to provide consent or complete follow-up. Or surrogate consent not available.
• Under age 50 years (more likely high energy, multiple injuries).
• Multiply injured patients who require prolonged thromboprophylaxis or delayed thromboprophylaxis initiation.
• Patient unable to attend follow-up visits.
• Currently incarcerated, at a correctional facility.