Posterior atlantoaxial 'facetal' instability associated with cervical spondylotic disease

Abstract

Aim: The association of single or multiple level cervical spondylotic disease with atlantoaxial instability is assessed. The implications of identifying and treating atlantoaxial instability in such an association are highlighted.

Materials and methods: The analysis is based on an experience with 11 patients treated during the period June 2013-June 2014. All patients had single or multilevel cervical spondylotic disease. The spinal canal compromise and evidence of cord compression was evident on imaging in the cervical subaxial spine and was related to disc bulges and osteophytic bars. There was no or relatively insignificant compression of the cervicomedullary cord by the odontoid process. There was no evidence of odontoid process-related instability on dynamic imaging. Apart from presence of features of cervical spondylosis, investigations and surgical exploration and direct manual handling of the facets revealed evidence of Type B (posterior) atlantoaxial 'facetal' instability in all patients. Our 5-point clinical grading system and Japanese Orthopaedic Association (JOA) scores were used to monitor the patients both before and after surgery and at follow-up. Surgery involved both at lantoaxial and subaxial cervical fixation. During the average period of follow-up of 9 months (5-17 months), all patients showed remarkable and gratifying neurological recovery.

Conclusion: We conclude that atlantoaxial facetal instability can be 'frequently' associated with cervical spondylosis and needs surgical stabilization. Our surgical outcome analysis suggests that missing or ignoring the presence of atlantoaxial facetal instability can be an important cause of suboptimal result or failure of surgery for cervical spondylotic myelopathy.

Keywords: Atlantoaxial dislocation; cervical spondylosis; facetal instability; segmental arthrodesis.

Figure 1

Images of a 65-year-old male patient. (a) T2-weighted MRI shows multilevel spondylotic changes. (b) MR image with slice through the facets. It shows posterior atlantoaxial facetal dislocation. (c) CT showing the cervical spine and the degenerative changes. (d) CT with slice through the facets showing posterior atlantoaxial facetal dislocation. (e) Postoperative scan showing atlantoaxial facetal alignment. Atlantoaxial and subaxial instrumentation can be seen. (f) Postoperative CT. Bone graft pieces can be seen in the midline. (g) Postoperative MRI. MRI = Magnetic resonance imaging, CT = Computed tomography

Figure 2

Images of a 52-year-old male patient. (a) T2-weighted MRI shows multilevel cervical spondylosis. (b) MRI slice through the facets showing posterior atlantoaxial dislocation. (c) CT reconstruction image showing the implants in atlantoaxial and subaxial regions