| Classification | Description | Notes |
| Type I | <3mm anterolisthesis, no angulation | Axial load, hyperextension |
| Type II | >3mm anterolisthesis, angulation; disruption of posterior longitudinal ligament | Hyperextension-axial loading force associated with severe flexion |
| Type IIa | Horizontal fracture line; angulation without anterolithesis | Flexion, distraction; mild or no displacement but very severe angulation |
| Type III | Type I with bilateral facet joint dislocation | Flexion, compression |
References:
Dreizin, D., et al. (2014). “Multidetector CT of blunt cervical spine trauma in adults.” Radiographics 34(7): 1842-1865.
Effendi B, Roy D, Cornish B, Dussault RG, Laurin CA. Fractures of the ring of the axis: a classification based on the analysis of 131 cases. J Bone Joint Surg Br 1981;63-B(3):319–327.
Levine AM, Edwards CC. The management of traumatic spondylolisthesis of the axis. J Bone Joint Surg Am 1985;67(2):217–226