A Study of Morphometric Anatomy of Axis Vertebrae and Its Clinical Importance

The axis (second cervical vertebra) is unique in possessing the dens or odontoid process and very specialized superior articular facets. The study was carried out to gather the metrical data of this atypical cervical vertebra. Forty dried intact human axis vertebrae were measured using digital vernier caliper accurate up to 0.01 mm. Various linear measurements of body, dens, pedicle, superior and inferior articular facets were studied .The mean width of the dense axis was 9.67mm and mean height was 11.84mm. The mean height of anterior corpus axis was 20.09mm.The mean maximum length and width of superior articular facet were15.37mm and 14.16mm respectively. All the measurement were observed to be more on the left side than on the right and all these differences were statistically insignificant. The data in this study should be useful to surgeons while working around the second cervical vertebra to avoid injury to the vital structures. The anatomy of the vertebrae exhibits complex, three-dimensional structures, showing extensive variability in morphology. Characteristics of the axis vertebrae must be noted before any spinal operation such as trans-pedicular screw fixation, trans-articular screw fixation, screw fixation of dens axis, inter-spinous wiring, and inter laminar clamp.