A new mechanism of injury in ankylosing spondylitis

Non-traumatic hyperextension causing atlantoaxial subluxation

D. Samartzis, H. N. Modi, K. M. C. Cheung, K. D. K. Luk


Ankylosing spondylitis (AS) is a progressive multisystem chronic inflammatory disorder. The hallmark of this pathological process is a progressive fusion of the zygapophyseal joints and disc spaces of the axial skeleton, leading to a rigid kyphotic deformity and positive sagittal balance. The ankylosed spine is unable to accommodate normal mechanical forces, rendering it brittle and susceptible to injury. Traumatic hyperextension injury of the cervical spine leading to atlantoaxial subluxation (AAS) in AS patients can often be fatal. We report a non-traumatic mechanism of injury in AS progressing to AAS attributable to persistent hyperextension, which resulted in fatal migration of C2 through the foramen magnum.

Cite this article: Bone Joint J 2013;95-B:206–9.


  • No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

  • Received March 10, 2012.
  • Accepted October 5, 2012.
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