Total aplasia of posterior arch of the atlas

Congenital anomaly-total aplasia of the posterior arch of the atlas vertebra is very rare, a developmental failure of chondrogenesis rather than the disturbance of ossification. Reported prevalence is 0.95-4%. In the present study the incidence of total aplasia of posterior arch of the atlas is 0.91% i.e., 1 in109 dried human adult atlas vertebrae. This atlas comes under the type E category according to the classification of congenital posterior arch defect proposed by currarino et al. This knowledge is essential for clinicians as new surgical techniques and instruments continue to evolve for the treatment of unstable cervical spine and also to avoid misdiagnosis among trauma victims and to provide information on its proper management.