Morphometric Study of the Atlas Vertebra using Manual Method.

ABSTRACT: The atlas (first cervical vertebra) has undergone many structural modifications. It is critically located and close to the 'life centres'. For this study, one hundred dried intact human atlas vertebrae from the Indian population were measured using a digital Vernier calliper that provides accurate resolution up to 0.01 mm. The distance between the tips of the transverse process, the outer and the inner distance between the foramen transversaria and various diameters of vertebral foramen were measured. The mean width of the measured atlases was 69.37 mm. The mean distance between the lateral margins of foramen transversaria was 55.66 mm and the inner distance was 45.93 mm. The mean thickness of vertebral artery grooves was 3.72 ± 1.06 mm. The observations made in the present study may help in improving understanding of various bony dimensions while operating close to important structures like nerve roots and the vertebral artery. KEY WORDS: Atlas, Atypical cervical vertebra, C1, morphology.