| Classification | Description | Notes |
| Type 1 | Fracture through posterior arch | Stable. Hyperextension injury |
| Type 2 | Fracture through anterior arch | Stable. Hyper flexion injury |
| Type 3 | Bilateral posterior with uni- or bilateral anterior arch | Stability depends on integrity of the transverse ligament. Axial load injury. “Jefferson Burst”. |
| Type 4 | Fracture through the lateral mass | Unstable. Axial load and rotation injury |
| Type 5 | Transverse fracture through anterior arch | Unstable. Avulsion of longus coli or atlantoaxial ligament |
References:
Dreizin, D., et al. (2014). “Multidetector CT of blunt cervical spine trauma in adults.” Radiographics 34(7): 1842-1865.
Bransford, R., et al. (2009). “Unilateral C-1 lateral mass sagittal split fracture: an unstable Jefferson fracture variant.” J Neurosurg Spine 10(5): 466-473.
Gehweiler JA Jr, et al. (1976). “Fractures of the atlas vertebra.” Skeletal Radiol 1(2):97–102.