Effect of low molecular weight heparin on fracture healing in a stabilized rat femur fracture model

The purpose of this study was to evaluate the effect of low molecular weight heparin (LMWH) on fracture healing in a standard stabilized rat femur fracture model. A closed, mid-diaphyseal transverse fracture was created in the right femur of Long-Evans rats after insertion of a 0.8-mm K-wire into the medullary canal. Animals were randomized to receive either LMWH (70 units/kg dalteparin) or an injection of normal saline daily for 2 weeks. Animals were sacrificed at 2, 3, and 6 weeks. Fracture healing was assessed by radiographs, histology, and mechanical testing. There were no significant differences between the control and LMWH groups in the percentage of animals with radiographic bridging callus at each time point. Histologic appearance of fracture healing was similar between the control and LMWH groups. There were no significant differences in the normalized mechanical properties of the control and LMWH groups at 2 and 3 weeks. At 6 weeks, the percent torque of the LMWH group was significantly greater than the control group ( p = 0.0072), however, there was no significant difference in the stiffness and energy absorption. Dalteparin, at the dosage used in this study, did not impair fracture healing in this standard stabilized rat femur fracture model.