Synostosis of atlas with occipital bone-occurrence and clinical application.

Synostosis also known as occipitalization of the atlas is a rare congenital malformation at craniovertebral junction. Atlas, the first cervical vertebra forms the ellipsoidal synovial joints with the condyles of the occipital bone. Rarely it gets occipitalized where the condyles fuse with the lateral masses of the atlas. During the morphometric study of hundred skulls in Department of Anatomy, Sri Guru Ram Das Institute of Medical Sciences and Research, Vallah, two skulls showed the incomplete occipitalization of the atlas vertebrae. The partial or complete assimilation of atlas may have resulted due to the disruption in the separation of caudal part of the first sclerotome from the cranial part of the first sclerotome.