Fractures of the dens complicating ankylosing spondylitis with atlantooccipital fusion.

Patients with ankylosing spondylitis are prone to fractures. Fractures tend to occur in the lower cervical spine disc space. We describe 2 patients with odontoid fractures. Both patients had atlantooccipital fusion which may have increased their susceptibility for dens fractures. One patient had Crohn's disease.