Posterior bridging of the atlas vertebra in south Indians.

ABSTRACT

The vertebral artery is vulnerable to compression in its course between foramen transversarium and the foramen magnum during extreme rotation of the head and neck. This situation may be aggravated by the presence of posterior or lateral bridge of the atlas and result in compromised blood flow. The incidence of the bony ring formed by posterior bridging has been demonstrated in atlases of various races across the world it varies between 1.875% to 29.2%. In an examination of sixty south Indian atlases it was found in 11.7% of the cases. The presence of this bony bridging should be taken in to account during a surgical manipulation of the cervical spine.