A lateral radiograph showing a small spicule (black arrowhead) on the posterior arch which might be a mildest form of ponticulus posticus. Note that the lateral portion of the posterior arch (white arrow) is thin and low while the height of the posterior portion of the posterior arch (white arrowhead) looks normal. If a screw insertion is started at the posterior portion of the posterior arch (white arrowhead), it could injure the vertebral artery.