Spinal fractures and pseudoarthrosis complicating ankylosing spondylitis: MRI manifestation and clinical significance

Purpose: To analyze magnetic resonance (MR) patterns of fractures and pseudoarthrosis of the ankylosing spondylitic spine, and related changes in the dura and adjacent soft tissue. Materials and Methods: Sixteen patients with radiographically evident fractures or pseudoarthrosis of the spine were included. Each underwent MR studies. Ten patients among them underwent surgical operations. Results: Both transdiscal (n = 12) and transvertebral (n = 4) fractures were identified. The levels were located from T9 to L3. Five of 16 patients had pseudoarthrosis. The fractures or pseudoarthrosis had two patterns: low signal on T1- and high signal on T2-weighted images, and low signal on both T1- and T2-weighted images. Disruption of anterior longitudinal ligament (ALL) was identified in 14 patients. Seven patients had vertebral translation, all had disruption of the ALL. Dural adhesions were noted in five patients and manifested as linear epidural enhancements with triangular blunt edges. Conclusion: MR patterns of ankylosing spondylitis are important in evaluating complications of fractures or pseudoarthrosis, as well as changes in dura, soft tissue, and ligaments.