Axial CT image shows double fractures of the anterior arch and a single fracture of the posterior arch of atlas (C1) (arrows) with mild displacement.
- C1 fracture believed to be due to compression causing fracture of the arch of atlas
- Often in combination with avulsion of the transverse ligament of the C1
- Simultaneous injuries to other C spine are common
- Three types: fracture of only anterior arch (type 1), fracture of only posterior arch (type 2), and fractures of both anterior and posterior arches (type 3)
- Type 3 fracture is unstable
- Fractures rare in children, but one needs to know that anterior synchondroses fuse at age 7, posterior at age 4.
- MDCT is imaging modality of choice, able to demonstrate fracture lines and degree of displacement
- On radiograph, displacement of the lateral masses may be seen on the odontoid view.
- Mimicker = failure of fusion of the vertebral arch, this pseudo-fracture lines are less sharply defined and/or sclerotic.
1. Imhof H, et al. Spinal Imaging, 2008.
2. Atlas Frx / Jefferson Fracture in Wheeless' Textbook of Orthopedics