Risk-Stratified Thromboprophylaxis Effects of Aspirin Versus Low-Molecular-Weight Heparin in Orthopaedic Trauma Patients

Saturday, October 21, 2023

10:55 AM – 11:01 AM PST

Location: 4B

Presenting Author(s)

RO

Robert V. O'Toole, MD

Professor, Orthopaedic Surgery
University of Maryland School of Medicine, R Adams Cowley Shock Trauma Center
Baltimore, Maryland, United States

Disclosure(s): imagen: Consultant (Ongoing), Stock Shareholder (excluding mutual funds) (Ongoing); lincotek: Other Financial or Material Support (Ongoing); stryker: Consultant (Ongoing)

Corresponding Author(s)

Nathan N. O'Hara, PhD

Assistant Professor
University of Maryland School of Medicine, R Adams Cowley Shock Trauma Center
Baltimore, Maryland, United States

Disclosure(s): Arbutus Medical Inc.: Stock Shareholder (excluding mutual funds) (Ongoing)

Co-Author(s)

DS

Deborah Stein, MD, MPH

Professor
Department of Surgery, University of Maryland School of Medicine
KF

Katherine Frey, PhD (she/her/hers)

Associate Scientist
Johns Hopkins University Bloomberg School of Public Health
Johns Hopkins University
Baltimore, Maryland, United States
GS

Gerard P. Slobogean, MD

Associate Professsor
University of Maryland School of Medicine, R Adams Cowley Shock Trauma Center
Baltimore, Maryland, United States
RC

Renan C. Castillo, PhD

Professor
Johns Hopkins Bloomberg School of Public Health
Baltimore, Maryland, United States
AC

Anthony R. Carlini, MS

Senior Research Associate
Johns Hopkins Bloomberg School of Public Health
Johns Hopkins Bloomberg School of Public Health
Baltimore, Maryland, United States
AC

Ashley Christmas, MD
JC

Joseph Cuschieri, MD
Reza Firoozabadi, MD, MA

Associate Professor of Orthopedics and Sports Medicine
University of Washington, Harborview Medical Center
Seattle, Washington, United States
GG

Greg Gaski, MD
EH

Elliott Haut, MD, PhD
MK

Matthew Kutcher, MD
DM

Debra Marvel, MA
William T. Obremskey, MD, MPH, FIOTA (he/him/his)

Director Orthopedic Trauma Fellowship and Research
Vanderbilt University Medical Center
Vanderbilt Ortho Inst
Nashville, Tennessee, United States

Group Author(s)

GM

Group METRC

Purpose: The PREVENT CLOT trial concluded thromboprophylaxis with aspirin was noninferior to low-molecular-weight heparin (LMWH) in preventing death in orthopaedic trauma patients. This secondary analysis sought to determine if the effects of aspirin versus LMWH differed based on patients’ baseline risk of venous thromboembolism (VTE).

Methods: This PREVENT CLOT secondary analysis included 12,211 adult patients indicated for thromboprophylaxis due to an operatively treated extremity fracture or pelvis or acetabulum fracture. We used the Caprini Score to calculate patients’ baseline risk of VTE, stratifying patients into risk quartiles ranging from low ( <1%) to high risk (>10%). The primary outcome was a composite of thromboembolic outcomes within 90 days. We assessed treatment effects using the win ratio method. This approach paired all patients in each treatment group and compared the outcomes hierarchically, starting with death, followed by pulmonary embolism, deep vein thrombosis, then bleeding when the patients could not be differentiated on a more severe outcome. The win ratio is the number of wins in the aspirin arm divided by the number of wins in the LMWH arm.

Results: In the high-risk quartile (n = 3052), 46% of patients had a femur fracture, 42% had a pelvis or acetabulum fracture, 48% had a thoracic injury, 39% had a spinal injury, and 35% had a head injury. Low-risk quartile (n = 3053) patients most commonly had a tibia fracture (67%), and few had thoracic (5%), head (1%) or spinal (1%) injuries. In the high-risk quartile, there was no significant difference in the effect of aspirin compared to LMWH on the composite outcome (win ratio, 0.95; 95% CI, 0.83–1.09, P = 0.48). This result was consistent in the low-risk quartile (win ratio, 1.09; 95% CI, 0.85–1.40, P = 0.51), low-medium risk quartile (win ratio, 1.01; 95% CI, 0.82–1.26, P = 0.90), and medium-high risk quartile (win ratio, 0.98; 95% CI, 0.83–1.15, P = 0.78).

Conclusion: Thromboembolic outcomes were similar when either aspirin or LMWH is used for prophylaxis. This result held true even when considering patients at highest risk of VTE.