Imaging features of spinal fractures in ankylosing spondylitis and the diagnostic value of different imaging methods

Our study aimed to characterize the imaging appearance of spinal fractures in ankylosing spondylitis (AS) and identify situations in which the use of magnetic resonance imaging (MRI) is necessary.

A total of 70 cases of spinal fractures associated with AS were retrospectively enrolled. Two radiologists independently reviewed the preoperative images. The location, type, ligament injury, neurological injury, and epidural hematoma following spinal fractures were assessed.

Only one patient had a vertebral compression fracture, and 69 patients had 77 transverse fractures involving three columns. The most frequent injuries in AS patients were type B3 (N=32, 43.8%) spine fractures, followed by type C (N= 20, 27.4%) spine fractures. There were significant differences in fracture types of the different spine regions (H=14.1, P<0.0001). Most type C spine fractures were located in the lower cervical spine, while most of the type B2 spine fractures were located in the thoracic spine. Transverse fractures were classified as shear or stress type fractures. In total, there were 62 shear fractures and 15 stress fractures. All of the transverse fractures were detected by computed tomography (CT). The accuracy of CT in the diagnosis of the exact anatomic involvement of transverse fractures was significantly higher than that of MRI (χ²=8.36, P=0.014). The anterior longitudinal ligament (ALL) was the most frequently torn ligament. Tears of ossified ligaments were best visualized by sagittal reformatted CT. Lower cervical fractures were more likely to be associated with neurological injury compared with fractures to other regions of the spine (χ²=7.24, P=0.025). There were six epidural hematoma cases, which were only detected by MRI, were found to have fractures of the lower cervical spine.

We recommend a whole-spine CT examination with three-dimensional reconstruction for detecting a suspected fracture in AS patients. In cases with neurological injury, MRI examinations are always mandatory. AS patients with lower cervical spine fractures require further investigation by MRI. Patients with non-lower cervical spine fractures without any neurological deficits do not need to undergo an immediate MRI.