[Fractures of the ankylosed spine: MRI features].

The diagnosis of transverse spinal fractures in patients with ankylosing spondylitis and Forestier's disease (DISH) may be difficult. The MRI features of 9 such fractures at the disk, vertebral body, spinal canal and posterior elements are presented. Fractures of the posterior elements (posterior arch fractures and/or rupture of interspinous or supraspinous ligaments and contiguous soft tissue structures) were present in all cases, underscoring the importance of MR signal abnormalities of posterior structures for diagnosis of these fractures. MR is advantageous due to its ability to demonstrate signal abnormalities of the posterior elements, which combined with disk and vertebral body abnormalities, play a major role for accurate diagnosis of this type of fracture.