A Morphometric study of Atlas and Axis articular surfaces with its implications during screw fixation for Atlantoaxial stability

Background: The Atlantoaxial joint is an important synovial joint that provides support and flexibility to the craniovertebral axis. Instability of the atlantoaxial joint occurs due to trauma, degenerative and inflammatory and congenital diseases. Morphometric measurements of the atlas and axis play an important role in spinal surgery to prevent neurovascular injury. This cross-sectional study will help in understanding the importance of dimensions of articular facets of atlas and axis vertebrae. Materials and methods: 138 intact dry specimens of each of the atlas and axis vertebrae of adults were studied. Various measurements were taken on atlas and axis with the help of Vernier caliper. Later the results were analysed statistically. Results: The mean anteroposterior diameter of the inferior articular facet of atlas was 17.73 and 17.64mm on the right and left sides. The mean transverse diameter of the inferior articular facet of atlas was 14.43 and 14.19mm on the right and left sides. The mean height and width of the dens facet were 9.86mm and 9.38mm. The mean anteroposterior diameter of the superior articular facet of the axis was 17.12 and 17.41mm on the right and left sides. The mean transverse diameter of superior articular facet of axis was 14.82 and 15.20mm on right and left side. The length, anteroposterior, and the maximum transverse diameter of dens were 16.14, 10.16, and 9.32mm. The mean IAF of atlas angle with sagittal plane on Right and left side were 14.29° and 14.32°. Conclusion: The results of this study will be helpful for better surgical intervention to prevent neurovascular injury and surrounding tissue injury during instrumentation and implant placement.