Disc problems may be classified by location/ zone as central, subarticular (lateral recess), foraminal, or extraforaminal. The most accepted nomenclature for disc lesions is the use of the term “protrusion” to describe bulging of an intact annulus, “extrusion” to describe contiguous nuclear material that has herniated through the annulus, and “sequestration” to describe a detached nuclear fragment. The ratio of the bulge “waist” to mass may also help define protrusion v.s. extrusion- i.e. protrusions have a wider annular base and extrusions have a narrower “stalk”. The degree to which the periphery of the disc is involved may further classify lesions as “focal,” meaning less than 25% of the disc circumference is displaced, “broad-based”, involving 25-50% of the perimeter, and “circumferential” involving 50-100%. (1)
Interestingly, large “extrusions” trigger a significant inflammatory response and generally regress more quickly when compared to contained “protrusions” that do not benefit from reabsorption. (2)
1. David F. Fardon, MD Nomenclature and Classification of Lumbar Disc Pathology SPINE Volume 26, Number 5, pp E93–E113
2. Morgan W. Management of Lumbar Disc Derangements. Presentation at the 2015 American College of Chiropractic Orthopedists Convention. Las Vegas NV April 25, 2015.
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