Does atlantoaxial dislocation influence the subaxial cervical spine?

Abstract

Previous studies have reported that the alignments of the occipital-cervical and subaxial spine were closely interrelated in asymptomatic individuals; however, none have focused on a population with atlantoaxial dislocation. From 2007 to 2011, 298 patients with atlantoaxial dislocation and atlas occipitalization were studied. Angles formed between Occiput-C2 and C2-C7 were measured. The relationship between the alignment of the occipital-cervical junction and the subaxial cervical spine was evaluated. The range of values for the angles measured was as followed: the Occiput-C2 angles were -35.2° to 44.8°, and the C2-C7 angles were -17.4° to 77.8°. Statistically significant negative correlations were observed between the Occiput-C2 and C2-C7 angles. Anterior dislocations of the atlas are associated with diminished lordosis or even kyphosis of the occipital-cervical junction, and result in compensatory hyperlordosis of the subaxial cervical spine, collectively presenting as a "swan neck" deformity. Atlantoaxial dislocation may influence the global cervical alignment.