Pseudo-Jefferson fracture

A pseudo-Jefferson fracture, or pseudospread of the atlas on the axis, refers to the normal overhanging of the lateral edges of the lateral masses of C1 over the lateral edges of the body of C2 seen in children. Most often, children will display this physiologically until about 7 years of age which is thought to be due to differential speed of growth of the atlas and axis. An accepted maximal value of normal overhanging is 6 mm when adding the offset of both the left and right sides .

It should not be mistaken for a Jefferson fracture.