Background The vertebral osteonecrosis (VON) is much less known and less frequently diagnosed than peripheral osteonecrosis. VON is considered as result of delayed consolidation of a compression fracture due to ischemia, which creates a cavity within the vertebral body that could get filled with gas and appearing in X-rays as a radiolucent linear or semilunar shadow known as the vacuum cleft sign. This sign could be more easily recognized in CT, and could get secondarily filled with fluid as detected by MRI. Several risk factors have been associated including trauma and osteoporosis, but it is important make a correct differentiation between VON and simple compression facture, because former is more associated with severe pain and neurological complications. Objectives To analyze the clinical and radiological characteristics in a series of 18 patients with VON. Methods Methods: We carried out a descriptive, observational, transversal study from the clinical records of 18 consecutive patients diagnosed with VON, referred to a monographic consultation of osteoporosis in a university hospital between April 2009 and November 2011. Analyzed data were demography, risk factors, clinical manifestations, radiological findings (X-rays, CT and MRI), treatment and outcome. Results Mean age of patients was 78.9 years, with 15 women (83.3%). Most frequent clinical complaint was acute back pain in 14 patients (77.7%), irradiated in 6 (33.3%). 61.1% referred moderated to severe pain, requiring third step analgesia in 38.8%. The mean time elapsed since pain onset until diagnosis was 7.3 months. Trauma history was detected in 55.5%, osteoporosis and previous compression fractures in 44.4%, vitamin D3 deficiency in 38.8%, chronic liver disease in 11.1%, previous use of systemic corticosteroids, intestinal malabsorption or neoplasm in 16.6, and radiotherapy or chemotherapy in 5.5%, respectively. Most frequent location of VON were T12 (44.4%) and L1 (16.6%), with multiple affected vertebrae in 4 cases (22.2%). The vacuum cleft sign was evident by X-rays in 15 cases and by CT in 3/5. MRI was done in 15 patients and most frequent findings were intravertebral liquid sign in 9 cases, empty and interface signs in 3 cases for each one. It was also found posterior wall displacement in 11 cases, with associated myelopathy in 2 (11.1%). There was clinical neurological involvement in 3 cases, one of them with paraparesis. The management was surgical in 1 case, vertebral cementation in 2 and orthopaedic in 15 (back brace). A HIV-infected patient presented concomitant osteonecrosis in peripheral locations too. Conclusions VON is an important differential diagnose of compression fracture because occurs in older people who have an increased prevalence of osteoporosis too. VON has an important delay in diagnosis because most of the specialists do not take it in account and the vacuum cleft sign is not always easy to identify in X-rays, appearing in some cases only with hyperextension. There are some clinical characteristics that could guide to ...