- Fractured ring of C1 due to axial load: A true Jefferson fracture is less common in children than in adults. It is caused by axial loading injuries and requires either two fractures of the C1 ring or one fracture in association with a congenital defect or unfused epiphysis.
- Synchondrosis may be injured by similar mechanisms in young children.
- Plain x-rays show abnormal position of lateral masses: Initial suspicion may be raised by overhanging lateral masses of C1 over C2 on the open-mouth odontoid x-ray. The rule of Spence can be used to identify a Jefferson fracture requiring treatment. If the total overhang of both C1 lateral masses on C2 is ³7 mm, the transverse ligament is probably disrupted and the spine is unstable (46).
- Pseudofractures in children: A true Jefferson fracture can be mimicked by pseudospread of the atlas in children. 90% of children up to 1–2 years of age have some pseudospread of the lateral masses of C1 over C2. This overhang of the lateral masses can be as much as 6 mm in children up to the age of 7 years.
- CT scan: Definitive diagnosis of fracturing of the ring of C1 is best made by CT scan.
Axial CT scan and 3D reconstruction of C1 ring injury in an infant: The anterior atlantal synchondrosis is “sprung.” There was no additional damage of the C1 ring. The injury was stable and was managed conservatively.