Role of Atlantoaxial and Subaxial Spinal Instability in Pathogenesis of Spinal "Degeneration"-Related Cervical Kyphosis

BACKGROUNDS: The role of subaxial and atlantoaxial instability in the pathogenesis of "degeneration"-related cervical kyphosis is evaluated. MATERIAL AND METHODS: During the period 2013-2016, the authors treated 21 patients having cervical kyphosis that was related to degenerative spinal disease. The patients presented with symptoms related to cervical myelopathy. Kyphosis was diagnosed on the basis of described radiologic parameters. The patients were divided into 3 groups. Group A (10 patients) had manifest radiologic evidence of atlantoaxial dislocation, type 1 facetal instability, abnormal increase in atlantodental interval, and evidence of cord compression by the odontoid process. Group B (5 patients) had axial or central atlantoaxial facetal instability (type 2 or 3 atlantoaxial facetal instability) and subaxial spinal instability. Group C (6 patients) had subaxial spinal instability. The patients were treated by only stabilization. Group A patients underwent atlantoaxial fixation, group B patients underwent atlantoaxial and subaxial fixation, and group C patients underwent only subaxial spinal fixation. The operation was aimed at arthrodesis of the spinal segments. No bone or soft tissue decompression was done. RESULTS: During the minimum follow-up period of 6 months, all patients improved in their neurologic symptoms and demonstrated evidence of spinal arthrodesis. There were no major surgical complications. CONCLUSIONS: Spinal instability plays a major role in the generation of cervical spinal kyphosis. Atlantoaxial instability may form the primary and nodal site of development of the process of spinal degeneration in general and kyphosis in particular.