Figure 12

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Nomenclature and Classification of Lumbar Disc Pathology

(Figure 12)

When a relatively large amount of disc material is displaced, distinction between protrusion (A) and extrusion (B or C) will generally only be possible on sagittal MR sections or sagittal CT reconstructions. In Figure C, although the shape of the displaced material is similar to that of a protrusion, the greatest cranio-caudal diameter of the fragment is greater than the cranio-caudal diameter of its base at the level of the parent disc, and the lesion therefore qualifies as an extrusion. In any situation, the distance between the edges of the base, which serves as reference for the definition of protrusion and extrusion, may differ from the distance between the edges of the aperture in the anulus, which cannot be assessed on CT images and is seldom appreciated on MR images. In the cranio-caudal direction, the length of the base cannot exceed, by definition, the height of the intervertebral space (Adapted from Milette PC. Classification, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:1267-1292)

Introduction

Preface	Introduction	Recommendations	Discussion (part 1)
Discussion (part 2)	Glossary	References	Appendix