Abstract

Heterotopic ossification (HO), the ectopic formation of bone in soft tissues, is a relevant musculoskeletal disorder that, by reduction of range of motion, may lead to significant impairment of quality of live. HO can either be acquired or hereditary. Acquired HO is seen most often after hip prosthetic surgery and pelvic trauma. In contrast, hereditary HO is commonly observed in the axial skeleton, but can affect every joint. Substantial effort has been directed towards understanding the pathophysiology and towards finding both, effective prophylactic and therapeutic treatments. Every improvement of the understanding of the pathophysiologic changes underlying HO as well as the rationale of prophylactic and therapeutic­ treatment regimens in the end, is based on the study of appropriate animal models. Although intriguing models of ‘genetic‘ HO have been developed recently, their relevance to acquired HO remains questionable. As there is still neither proper treatment nor reliable prophylaxis, animal models will remain important in the study of HO. Currently, there are 6 different animal models regularly used for the study of acquired HO. Some of these models can reflect a merely particular part of the disease. Hence, selection of the appropriate animal model for the study of HO is exceedingly important. The present paper reviews the history and major features of the different animal models of acquired HO, and reveals some of the insights gained through the study of animal models?; important biochemical and pathophysiological key features are highlighted. Clinical studies have proved indo­metacine, celecoxib and radiation therapy to be effective in reducing the occurrence of HO, but not always be able to prevent it.