The relationship between periosteum and fracture healing.

Fracture healing is a complex process that involves presence of osteoprogenitor cells and growth factors. Therefore, the integrity of the fracture site surrounding tissues including periosteum is necessary in order to provide the resources for bone regeneration. The purpose of this review is to organize and synthesize the relevant information regarding periosteum and fracture repair. Periosteum cells are involved in endochondral or intramembranous ossification according to the presence of a new formed cartilage. The periosteal osteoprogenitor mesenchymal cells differentiation is guided by a multitude of signaling molecules, especially bone morphogenetic protein 2 (BMP2), but also as a response to mechanical stimuli. If the periosteum is traumatized or removed, there are other osteoprogenitor cell sources as the ones located in the medullar cavity of the bones, the pericytes from the blood vessel walls as well as the undifferentiated cells from the adjacent soft tissue, muscles and fascia. However, total absence of the periosteum and lesions of the intramedullary vascular network is associated with fracture non-union. In these cases, muscular tissue surrounding the site could take over some of the cambium functions. In conclusion, there are other factors that can influence significantly fracture healing, besides periosteum.