Vertical mobile and reducible atlantoaxial dislocation. Clinical article.

OBJECT: The authors' experience with treatment of 8 patients with "vertical mobile and reducible" atlantoaxial dislocation is reviewed. The probable pathogenesis, radiological and clinical features, and management issues in such cases are discussed.

METHODS

Between January 2006 and March 2008, 8 patients who presented with vertical mobile and reducible atlantoaxial dislocations were treated at the Department of Neurosurgery at King Edward Memorial Hospital in Mumbai, India. The vertical atlantoaxial dislocation/basilar invagination reduced completely on extension of the neck, with no need of any cervical traction. According to the extent of superior migration of the odontoid process, and measurements based on the vertical atlantoaxial instability index, the dislocation was graded as mild, moderate, or severe. All patients were treated using the C-1 lateral mass and C-2 pars plate and screw method of fixation.

RESULTS

The study group was composed of 5 male and 3 female patients (mean age 24 years, age range 8-54 years). All patients presented with the physical features of short neck, torticollis, pain in the nape of the neck, and varying degrees of quadriparesis. In 6 patients there was a history of trauma prior to the onset of major neurological symptoms. The dislocation was mild in 3 cases, moderate in 1, and severe in 4. All patients had clinical neurological improvement following surgery. The follow-up duration ranged from 4 to 30 months (mean 18 months).

CONCLUSIONS

Vertical mobile and reducible atlantoaxial dislocation is a discrete clinical entity. Abnormal inclination and incompetence of the facet joint appears to be the primary causative factor that resulted in vertical dislocation or basilar invagination. Posterior fixation in the reduced dislocation position forms the basis of treatment.