Dagger sign (spine)

Last revised by Wasif Yasin on 27 Nov 2023

The dagger sign is a radiographic feature seen in ankylosing spondylitis as a single central radiodense line on frontal radiographs related to ossification of the supraspinous and interspinous ligaments secondary to enthesitis 1. It is possible for the radiodense line to extend into the sacrum 2

Radiographic features

On plain frontal radiographs it is noted as a linear increased density running along the spinous processes 3.


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