The fluid sign is one of the radiological features of osteoporotic fractures, and can be helpful in distinguishing them from metastatic vertebral fractures, as it is seen more often in osteoporotic fractures and is rarely seen in metastatic fractures 1. It is not as helpful as identifying a paravertebral/epidural soft tissue mass or infiltration of the pedicle or to other vertebrae, but those features are not always present in metastatic disease.
The finding correlates with vertebral osteonecrosis 1,2. The pathogenesis may be avascular necrosis (Kümmell disease) or due to acute insufficiency fracture in the setting of osteoporosis 1.
The "fluid sign" in vertebral collapse is deﬁned as a horizontal focal, linear, or triangular area of fluid intensity (hypointense on T1, hyperintense on T2/STIR) on a background of diffuse marrow edemalike signal in the vertebral body because of acute collapse.
- 1. Baur A, StäBler A, Arbogast S et-al. Acute osteoporotic and neoplastic vertebral compression fractures: fluid sign at MR imaging. Radiology. 2002;225 (3): 730-5. Radiology (full text) - doi:10.1148/radiol.2253011413 - Pubmed citation
- 2. Lin CL, Lin RM, Huang KY, Yan JJ, Yan YS. MRI fluid sign is reliable in correlation with osteonecrosis after vertebral fractures: a histopathologic study. (2013) European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. 22 (7): 1617-23. doi:10.1007/s00586-012-2618-z - Pubmed