A quantitative analysis of atlas vertebrae and its abnormalities

Introduction: The anatomy of the atlas vertebra reveals complex, three-dimensional structures, showing extensive variability in morphology. Features of the atlas vertebra must be familiar before any spinal surgeries such as transpedicular screw fixation, transarticular screw fixation, interspinous wiring, and interlaminar clamp. So, this study was undertaken to assess the various dimensions of the first cervical vertebra and evaluate their relationship with the vertebral artery foramen, and also to decide the safe locations for different surgical methods. Materials and Methods: In this study, thirty five dried specimens of atlas vertebrae were examined. Various dimensions of the vertebrae were measured, using vernier calliper and any abnormalities present in it were noted down and photographed. Statistical analyses of the measurements were done. Results: Abnormal foramina and retroarticular canal were seen in 5.7% of specimens. Incomplete foramen transversarium were seen in 8.57% of specimens. Mean of all parameters of atlas were tabulated. Commonest shape of superior articular facet was oval in 42.8% of specimens. Conclusion: The knowledge of these measurements and the variations present may be of importance to orthopaedic surgeons, neurosurgeons. This information may also be helpful in avoiding and reducing complications such as vertebral artery injury, spinal cord injury during spine surgeries.