CERVICAL MYELOPATHY CAUSED BY PSEUDARTHROSIS BETWEEN THE ATLAS AND AXIS ASSOCIATED WITH DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS

Study Design. This is a report of a patient with severe cervical myelopathy due to pseudoarthrosis between the posterior tubercle of the atlas and the spinous process of the axis, associated with diffuse idiopathic skeletal hyperostosis. Radiographs of 170 patients with neck pain were reviewed to identify lesions involving abnormal contact between the atlas and axis. Objective. Based on an analysis of 170 radiographs, prevalence of condition was estimated. Summary and Background Data. A number of histologic studies on pseudoarthrosis involving the lumbar spine have been reported. In contrast, lesions between the posterior tubercle of the atlas and the spinous process of the axis have not been reported in association with cervical myelopathy. Methods. Clinical and pathologic features of a patient with pseudoarthrosis between the posterior tubercle of the atlas and the spinous process of the axis were investigated. Radiographs of 170 Japanese patients over 40 years old were examined, and abnormal contact between the atlas and axis was classified into three patterns. Patients also were classified into two groups based on the degree of spinal hyperostosis. Results. Of 170 patients, 53 showed abnormal contact between the atlas and axis. The prevalence of abnormalities in the pronounced hyperostosis group (Forestier's stages II and III) was much higher than in the group with normal or slight hyperostosis. Two men had radiographic patterns showing osteophytes projecting into the spinal canal and associated with marked cervical myelopathy. Conclusion. ln the group with pronounced hyperostosis, pseudoarthrosis or a variant can cause serious problems in the upper cervical spine that should not be overlooked.