Variable Morphology of the Axis Vertebrae in 100 Specimens: Implications for Clinical Palpation and Diagnostic Imaging

ObjectiveThe purpose of this study was to investigate and measure the variable morphologies of axis vertebrae and explore the clinical significance of variations as it may pertain to clinical palpation and diagnostic imaging.MethodsThe common variable morphologies in 100 specimens of intact dry adult axis vertebrae (Chinese) were investigated and measured. The frequencies in deviation of odontoid processes, deviation of spinous processes, and presence of bifid spinous processes were observed. The distances between the apices of transverse processes and inferior articular facets were also measured.ResultsVariable morphologies of C2 that we observed were deviation of odontoid processes (14 cases, 14.0%), deviation of spinous processes (3 cases, 3.0%), and bifid spinous processes (95 cases, 95.0%). Of the bifid spinous processes, 56 had a process on the left side equal to the right side, 21 were longer on the left, and 18 were longer on the right. The distances between apices of transverse processes and inferior articular facets in the left side of C2 were 17.67 ± 2.47 mm, and that of the right side were 17.81 ± 2.55 mm.ConclusionsBecause variable morphology of the axis is common, congenital deviation of the odontoid process, deviation of the spinous process, and asymmetrical bifid spinous processes should be taken into account during clinical palpation and diagnostic imaging.