Ankylosing Spondylitis Manifested by Extensive Cervical Erosions with Spontaneous Anterior Atlantoaxial Subluxation

Atlantoaxial instability owing to bone erosions in a patient with ankylosing spondylitis (AS) is rare. We describe the radiographic characteristics, pathology, and treatment of a patient with this rare clinical manifestation and review the literature.

A 36-year-old man with an 8-year history of AS presented with progressive neck pain, low back pain, hand numbness, and limited mobility of the neck. Cervical radiography showed anterior atlantoaxial subluxation with bone erosions at the odontoid process and a mass lateral to the atlas and edge of vertebrae. AS was diagnosed according to the modified New York criteria, and the patient underwent a posterior C0-C6 occipitocervical arthrodesis surgery and C3-C6 laminectomy to reconstruct atlantoaxial stability and relieve cervical compression. The symptoms of neck pain and hand numbness improved at the 1-year follow-up, and the patient completely resumed normal activities. Imaging showed realignment of C1-2 with complete decompression of the spinal cord and fusion of the atlantooccipital joint. The internal fixation has remained stable, and progressive bone erosion changes were not found after surgery.

Extensive cervical erosions with spontaneous atlantoaxial subluxation in AS is extremely rare. The erosive change of atlantoaxial bone may be an early feature of AS. Cervical spine radiographs are essential for patients with AS who present with neck pain. Complete decompression and internal fixation are necessary to prevent serious neurologic morbidity from spinal cord injury in such patients.