From the case:
Dagger sign in ankylosing spondylitis
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Dagger sign (Ankylosing spondylitis)
The dagger sign is a single central radiodense line on frontal radiographs related to ossification of supraspinous and interspinous ligaments.Note the inflammatory involvement of the right hip as well.
Case Discussion
The dagger sign is a single central radiodense line on frontal radiographs related to ossification of supraspinous and interspinous ligaments.