 In non-bisphosphonate cases of ONJ, it is mainly the cancellous portion of the bone and its marrow content that are involved in the disease process.The first stage is an oedema of the bone marrow initiated by a bone infarct, which is itself modulated by numerous causes, leading to myelofibrosis as a result of hypoxia and gradual loss of bone density characteristic of ischaemic osteoporosis.Further deterioration can be triggered by additional bone infarcts leading to anoxia and localized areas of osteonecrosis within the osteoporotic cancellous bone.