Rivaroxaban does not impair fracture healing in a rat femur fracture model: an experimental study

Background: The prescription of the oral anticoagulant rivaroxaban to prevent thromboembolic episodes associated with orthopaedic surgery has dramatically increased since it was introduced. Rivaroxaban is beeing prescribed although recent in-vitro studies revealed that it impaired osteoblast metabolism. In this study we analysed the effect of rivaroxaban on fracture healing in a rat femur fracture model. Methods: Femur fractures were created by a 3-point-bending device in 48 Wistar rats and subsequently stabilized by intramedullary nailing. After the surgical procedure animals were randomised into four groups. Two groups were fed with 3 mg rivaroxaban per kg body weight per day and two control groups were fed with chow only. Animals were euthanized 28 or 49 days after surgical procedure. Femurs underwent undecalcified histologic staining micro CT scanning and biomechanical testing. The statistical significance was evaluated using one-way Anova with Bonferroni correction. Results: Micro CT-scans revealed significantly increased volume of bone tissue in the fracture zone between day 28 and 49. During the same time callus volume decreased significantly. Comparing the fracture zone of the rivaroxaban group to the control group the treated group revealed a larger callus and a marginal increase of the tissue mineral density. The torsional rigidity was not influenced by the treatment of rivaroxaban. Conclusion: In the present study we were able to demonstrate that rivaroxaban does not impair fracture healing in a rat femur fracture model. Considering the fact that low molecular weight heparins delay fracture healing significantly, rivaroxaban might be an improved alternative.