The pattern of new bone formation in isografts of bone

The pattern of new bone formation has been studied in isografts of fresh iliac bone and also in isografts of dead or irradiated iliac bone. Two phases of osteogenesis have been found in some fresh grafts. An early phase occurs during the first 3 weeks after transplantation, whilst the second phase is found after 8 weeks. The first phase is absent from non-viable grafts and it is therefore concluded that cells of the grafts are largely responsible for this early osteogenesis. The second phase, it is suggested, has a major host component, and may be due to induction of osteogenic potential in host mesenchymal cells. There may be some dependence of the second phase on the first but the extent is not clear. Removal of the bone marrow from the graft has little effect upon the first phase of new bone formation and it is suggested that surviving endosteal cells are the main participants in early osteogenesis.