Experimental models of fracture repair.

Many mammalian and avian species have been used as models to study fracture healing. The individual animals, based on their size and other characteristics, are used to show the effects of different interventions on healing bone. The models may have fractures created by closed or open means or osteotomies. Fracture healing can be evaluated through histologic, mechanical, chemical, or biological studies. Internal fixation, external skeletal fixation, or no fixation may be used in the experiments. Results of fracture healing studies among animal species may conflict even when the same model is used in each species. These differences may be explained by anatomic, biochemical, and gene expression differences. Evaluation of the animal model is an important consideration when applying the results of any particular study to humans. Consensus regarding fracture healing develops from agreement between results of animal models and human clinical studies.