Fluid sign (vertebral collapse)

Last revised by Sonam Vadera on 11 Nov 2022

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.

Radiographic features


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 edema-like signal in the vertebral body because of acute collapse.

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