STUDY DESIGN. The study consisted of a retrospective and a prospective study part. OBJECTIVE. We aimed to investigate the nature of the intravertebral vacuum clefts (IVC) in computed tomography (CT) in acute osteoporotic vertebral fractures in correlation with magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA. IVC and intravertebral fluid accumulations have been shown to be indicative of benign vertebral fractures in CT and MRI, respectively. METHODS. Twenty-eight patients (30 osteoporotic fractures) associated with intravertebral vacuum in CT in whom MRI of the spine was performed were retrospectively analyzed. Moreover, we prospectively performed MRI examinations in 12 consecutive patients with 13 osteoporotic fractures with an intravertebral vacuum in CT. T1-w SE, STIR, and 5 repetitive T2-w TSE studies were performed (1.5 Tesla system, Siemens). Two experienced readers assessed the examinations in consensus with regard to the occurrence and location of the intravertebral and intradiscal vacuum on CT and the corresponding signal alterations in MRI. RESULTS. Twenty-seven (90%) of the retrospectively analyzed fractures with intravertebral vacuum in CT showed a fluid like signal in the location of the vacuum in MRI. In the prospective group, a small fluid-like signal was initially present on T2-weighted sequences in 11 of 13 fractures (84.6%). During the repeated T2-weighted measurements, the fluid occurred or increased markedly in all cases. An intradiscal fluid was present either initially and/or during the course of the examination in 46% of the prospective cases and in 50% of the retrospectively evaluated fractures. CONCLUSION. The occurrence of the fluid in MRI within intravertebral clefts is a dynamic process, which is dependent on the position of the patient and is presumably secondary to the extension momentum in the supine position. This may be due to the negative pressure in the horizontal position in which the fracture site is distracted. intravertebral.