Shiny corner sign (ankylosing spondylitis)
The shiny corner sign is a spinal finding in ankylosing spondylitis, representing reactive sclerosis secondary to inflammatory erosions at the superior and inferior endplates (corners on lateral radiograph) of the vertebral bodies which are known as Romanus lesions. Eventually, the vertebral bodies become squared (see vertebral body squaring for other causative entities).
There is ongoing international debate about specificity. Although axial spondyloarthritis is characterized by typical MR imaging features , these findings may not be totally specific and may be seen in degenerative or other spinal disorders as well , as all forms of spondyloarthritis may ultimately develop into ankylosing spondylitis in patients with longstanding disease .
Triangular regions of sclerosis are classically seen at the superior and inferior vertebral endplates anteriorly (corners). This occurs as a response to inflammatory Romanus erosions, which may be seen concomitantly with the sclerotic "shiny corners".
MR imaging allows for the detection of Romanus lesions and shiny corners in both early and late spondyloarthritis, respectively .
In active disease, these lesions are depicted as reduced signal intensity of the rim of the endplate on T1 images and as increased signal intensity on STIR images, representing bone marrow edema or osteitis. At this stage, plain films appear normal or may show Romanus erosions. Later in the disease course, the epiphyseal ring can appear hyperintense on T1WI. Such hyperintense lesions represent circumscribed areas of postinflammatory fatty bone marrow degeneration. Only at this stage are shiny corners depicted by conventional radiography - that is, long after inflammation has run its course.