An experimental model for non-union in rats.

Few studies of the biological changes which occur in impaired fracture repair and non-union have been carried out, and creating an appropriate model for advanced biochemical studies of non-union has proved to be a demanding task. This paper presents a standardized experimental model for producing non-union in rat femurs, for use in biochemical studies of non-union. A mid-diaphyseal fracture with a rotationally unstable fixation was performed in rats with a mean weight of over 330 g and mean age of over 10 weeks. Radiologically and histologically (Alcian blue and Safranin O stainings) the signs of undisturbed fracture healing were observed until 3 weeks after the fracture. Thereafter there was evidence that chondrocytic activity ceased, with no signs of formation of calcifying bridging callus. From the seventh week onwards, all elements necessary for a calcifying callus were lost; and the histological picture tended to be of scar tissue bond between the fracture ends.