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



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.