Morphological and Morphometric Analysis of Superior Articular Facet of Atlas Vertebra.

INTRODUCTION

The first cervical vertebra, also referred to as the atlas, forms a vital part of the craniovertebral junction (CVJ). The anatomy of the atlas is essential to understand the basis for CVJ anomalies and their surgical correction. The present study was undertaken to provide accurate morphometry and describe the morphological variations of the superior articular facet (SAF) of the atlas.  Methods: In this observational, cross-sectional study, the length and width of the SAF of 150 atlas were measured using a digital caliper. The variations in the morphology of the SAF in the same bones were also recorded. Z-test was applied to find the statistically significant difference between the measurements of the SAF of the atlas on the right and left sides. p-value ≤ 0.05 was considered statistically significant.

RESULTS

The width of the SAF of the atlas was found to be significantly (p < 0.001) greater on the left side (8.76 mm to 14.84 mm) compared to the right (7.67 mm to 14.83 mm). The mean length of the SAF was 21.1 mm and 21.9 mm on the left and right sides, respectively. Morphologically, four variations of superior articular facets were noted: oval, bilobed, kidney, and dumbbell shaped. The most common variation was an oval-shaped facet with a prevalence of 66.7% on the left side and 57.3% on the right. The least common variation was the bilobed facet, with a prevalence of 4% on the left side and 8.7% on the right.

CONCLUSION

The width of the SAF of the atlas was statistically significant on the left side. Morphologically, four types of variations were observed in the shape of the SAF. Knowledge of the morphological and morphometric variations of the SAF can be of help during surgical approaches at the CVJ.