Imaging description

Ankylotic spine disorders, including seronegative spondyloarthropathy (especially ankylosing spondylitis) and diffuse idiopathic skeletal hyperostosis (DISH), result in osseous fusion of the vertebral elements which restrict physiologic motion of the vertebral column and predispose the spine to atypical fractures even with minimal trauma.

Radiographs may not delineate the subtle fractures often seen in ankylotic disorders (Figure 28.1). It can also be difficult on radiographs to determine the full extent of the fracture (Figure 28.2), differentiate incomplete ankylosis from fracture, or evaluate the soft tissues. For these reasons, when ankylosis is encountered, the radiologist must have a high level of suspicion for an occult fracture, and CT or MR should be utilized liberally.

Injuries in the setting of ankylosis often involve all three spinal columns [1]. MR is superior for the evaluation of the disk space, soft tissues, and spinal cord. Soft tissue trauma including ligament tears and transdiskal injuries may be diagnosed on CT by subtle widening of the intervertebral space compared to adjacent levels [2]. CT angiography or MR angiography may also be necessary to evaluate for vascular injury if the fracture extends to the foramen transversarium.