There is a lucent lesion in the vertebra (right image), nicely targetted via a transpedicular approach with CT guidance.

The procedure took under half an hour, with a small amount of discomfort to the patient (aided by a generous dose of local anaesthetic), when in the past, this would have required open surgery. The patient was on his feet and shopping within 2 hours. Modern medicine!

What are the radiological signs for this condition?

The spine radiographs reveal fusion of the sacroiliac joints. The enthesophytes are not well demonstrated radiographically, unlike on CT. In fact, there's also ankylosis of the facet joints, and the interspinous ligaments- giving rise to the dagger sign. There is also increased density of the vertebral corners (shiny corners). (You'd also look out for endplate erosions secondary to inflammatory discitis- the Anderssen lesion).

 

All keywords for the diagnosis of ankylosing spondylitis.

 

But wait! Look at the CT image (2nd row, 1st image)- there's a chalk fracture. This is the dangerous thing about ank spond: the entire spine is fused as a brittle single column, and a fracture easily propogates through (like a Chance fracture). The cord is therefore at risk, and an MRI will be useful to evaluate for cord injury.