This is a report of two patients who sustained cervical myelopathy that seemed to be associated with hypertrophic atlantodental osteoarthritis accompanying dens hypertrophy.
Pathogenesis of hypertrophic osteoarthritis in the atlantodental articulation was elucidated, and these two patients were treated by C1 decompressive laminectomy with or without posterior fusion.
One case of myelopathy resulting from the hypertrophic nonunion of the dens has been reported, but to the authors' knowledge, there have been no reports describing a case similar to those presented in this report.
History, physical findings, and image examination findings common to the two cases were analyzed to elucidate pathogenesis of hypertrophic osteoarthritis in the atlantodental articulation. C1 decompressive laminectomy alone was performed in one patient and additional atlantoaxial transarticular fixation in the other patient.
Myelopathy in two patients was caused by the cervical cord compressed between the hypertrophic and sclerotic dens and the anteriorly displaced posterior arch of the atlas in the developmentally small atlas ring. Postoperative neurologic recovery was satisfactory with the atlantoaxial solid fusion.
The atlantodental hypertrophic osteoarthritis accompanying the dens hypertrophy seemed to have developed because of post-traumatic atlantoaxial instability. Their developmentally small atlas ring may be a predisposing factor toward the development of myelopathy.