Morphometric analysis of the lateral mass of atlas and its clinical significance in craniovertebral junction surgeries.

Background: The surgery at the craniovertebral junction (CVJ) area needs meticulous knowledge of the atlas vertebra which forms the CVJ. The screws need to be placed in the lateral mass of the atlas to stabilize the C1 and C2 joints in case of CVJ anomalies. Our study aimed to determine the dimensions of the lateral mass in dry bones for the accurate placement of screws.

Methods: We have analyzed 82 dried atlas vertebrae and measurements of inferior articular facet (IAF) in terms of length, breadth, height, and angles were done.

Results: The length of IAF was 17.93 ± 0.76 mm and 18.01 ± 0.75 mm on the right and left side, respectively (P = 0.0038). The mean width was 14.88 ± 0.85 mm on the right and 14.86 ± 0.79 mm on the left side. The mean distance measured between the posterior arch of the atlas to the anterior margin of IAF was 22.87 ± 0.60 mm on the right side and 22.79 ± 0.61 mm on the left side (P = 0.0247). The horizontal thickness of lateral mass on the right and left sides were 15.91 ± 1.73 mm and 15.83 ± 1.56 mm, respectively, with a P-value of 0.3771. The angle measured for the screw trajectory in lateral mass of the atlas was 16.61 ± 1.49 on the right side of vertebrae and 16.53 ± 1.43 on the left side.

Conclusion: The study provided comprehensive data on the approximate screw length needed for the lateral mass of atlas in an adult patient. The detailed morphometric measurements provided in this study offer valuable insights that can help surgeons optimize surgical planning, potentially reducing complications and enhancing patient outcomes in craniovertebral junction procedures.