New bone formation in the intervertebral joint space in spondyloarthritis: An MRI study

Objectives: To study the presence of high signal intensity of the intervertebral disc, syndesmophytes, vertebral corner bridging and transdiscal ankylosis on spinal T1-weighted MR images in spondyloarthritis (SpA). Methods: A retrospective case-control study of whole spine MRI examinations, obtained in 100 patients with axial SpA and in 100 control patients, was performed. All disco-vertebral units (DVUs) were analyzed on T1-weighted MR images for normal or high signal intensity of the intervertebral disc, presence of syndesmophytes, vertebral corner bridging or transdiscal ankylosis and correlated with final diagnosis. Sensitivity, specificity, and positive and negative likelihood ratios were calculated. Results: In this study group, intradiscal high signal intensity, vertebral corner bridging and transdiscal ankylosis on T1-weighted MR images of the spine were all highly specific (specificity: 100%) for diagnosis of axial SpA. However, these signs all had low sensitivity (vertebral corner bridging: 15.0%; intradiscal high signal intensity on T1-weighted MR images: 12.0%; transdiscal ankylosis: 8.0%). Syndesmophytes on spinal MRI were observed in 25 patients but had a more limited diagnostic value (sensitivity: 16.0%, specificity: 91.0%). Conclusions: When present in a patient with inflammatory back pain, intradiscal high signal intensity on T1-weighted MR images could be a specific and reliable sign of the presence of axial SpA. Vertebral corner bridging and transdiscal ankylosis also show potential as specific and reliable signs of axial SpA. In contrast, syndesmophytes on MRI do not show potential as a specific or reliable sign of axial SpA.