Odontoid fractures usually occur with forceful distension of the cervical spine. They are normally divided into three types:
Type I Odontoid Fracture
- Fracture above insertion of transverse ligament: This is a fracture of the odontoid process at its rostral end and is usually stable.
- Must be differentiated from persisting ossification center: This fracture can mimic a persisting ossiculum terminale, a congenital secondary ossification center at the rostral end of the odontoid.
Type II Odontoid Fracture
- Fracture across base of the odontoid process: The location of this fracture is below the transverse ligament, and it is usually unstable.
- Must be differentiated from persisting os odontoideum: This fracture can be mimicked by os odontoideum, a congenital failure of fusion of the odontoid process to the base. It is also unstable in most cases.
- Fracture through growth plate: In children, epiphysiolysis may also occur and is usually unstable.
Type III Odontoid Fracture
- Fracture through C2 body: The type 3 fracture is through the vertebral body of C2 below its juncture with the odontoid. It may be stable or unstable depending on amount of body involvement
- Frequently unstable: If fracture prevents the transverse ligament from applying force to the body of C2 then consider fracture unstable
- Epiphysiolysis Injury of the odontoid: This is a fracture of the odontoid that is peculiar to young children. It occurs at the dentocentral synchondrosis.