MRI arthography (MRA) is commonly used in the investigation of shoulder instability. However many surgeons are now using CT arthography (CTA) as their primary radiological investigative modality. They argue that CTA is cheaper, and give satisfactory soft tissue images in the “soft tissue window” mode. They believe that CTA give superior images when looking at bone loss and bony defects, and as such is more useful in deciding whether a patient requires an open procedure or not.

In this study we aimed to compare the results of MRA and CTA in the investigation of shoulder instability.

We reviewed the operative and arthographic findings in all patients who had surgery for shoulder instability in our unit over a 4 year period. We compared the results of the arthograms with the definitive findings found at the time of surgery. All arthograms were performed by standard techniques and were reported by musculoskeletal radiology consultants. All surgery was performed by experienced consultant shoulder surgeons.

In total 48 CTAs and 50 MRAs were performed. We found that there was no significant difference between the two wrt sensitivity (p=0.1) and specificity (p=0.4) when looking at labral pathology. However CTA was more sensitive at picking up bony lesions (p< 0.05).

This study supports the view that CT arthography is the superior radiological modality in identifying pathology when investigating patients with shoulder instability. It is cheaper and better tolerated by patients than MRA and gives useful information on whether a patient needs an open or arthroscopic stabilisation procedure.