Notes: Annulus fibrosis in green, nucleus pulposis in red
Pedicle removed on lateral illustrations for clarity
| Classification | Description | Notes |
| Annular Tear | Disruption of the annulus fibrosis without change in the outer contour | Not considered a herniation |
| Focal Herniation | Involves less than 25% of the circumference of the disc | |
| Broad-based Herniation | Involves 25-50% of the circumference of the disc | |
| Symmetric Disc Bulge | Involves more than 50% of the circumference of the disc | Not considered a herniation |
| Classification | Description | Notes |
| Protrusion | Greatest dimension of extra-annular disc material is less than that of the plane of contact with the annulus | |
| Extrusion | One measure of extra-annular disc material exceeds the diameter at the plane of contact with the annulus | |
| Migration | Any displacement of a fragment away from its site of origin | A subset of extrusion |
| Sequestration | Displaced fragment that loses contact with its site of extrusion | A subset of extrusion |
Reference:
Fardon, D. F. and P. C. Milette (2001). “Nomenclature and classification of lumbar disc pathology. Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology.” Spine 26(5): E93-E113.