Pseudosubluxation of the axis in young adults.

Pseudosubluxation or anterior slippage of the axis on C-3 is a well recognized physiologic phenomenon in children. Because of a downward shifting of the apex of flexion of the cervical spine that occurs at about age 10, this physiologic offset of C-2 has been thought unlikely to occur in older individuals. However, a review of a series of flexion and extension cervical spine films showed six such cases in the 14- to 21-year age range.