Methodological Consideration of Various Intraosseous and Heterotopic Bone Grafts Implantation in Animal Models

Bone fracture healing is a complex process including inflammation, repair and remodeling. Bone grafts or substitute are widely accepted to treat impaired healing. Newly developed bone substitutes must undergo in vitro and in vivo testing before clinical application. All kinds of intraosseous and heterotopic implant models in small and/ or large animals are used for different bone substitutes. Orthotopic implant at models is used for evaluation of graft materials. Based on the statistic of literatures, we find small animals should be used first before large animal as osseous defect models. Rabbit and rat are the commonly chosen animals, while femur and calvaria are the most implanted anatomic sites. Critical size defect models are useful as bone defect model, but vary considerably between animals. Typical heterotopic ossification after implantation of bone substitute is found almost in all species of animals. No bone formation is found after subcutaneous implantation of bone granule grafts in small animal, but in large animal. In contrast, bone block grafts show a distinguished result of bone formation in small animals as well as in large animals. This article reviews currently animal bone defect models and anatomic implant site for bone graft, gives a recommendation for the future research.