Intervertebral Disc
Classification of Disc Disorders
Disc Herniation: Disc herniation is defined as a localized displacement of disc material beyond the outer limits of the intervertebral disc. The material may consist of a portion of the gel-like nucleus, bone fragments, annular tissue or cartilage. A herniation may be further categorized as focal (< 25%of disc circumference) or broad based (between 25 and 50% of disc circumference). A herniated disc may present as a protrusion (contained herniation) or as an extrusion. An extrusion is associated with migration of disc material completely through the outer annular fibers of the disc. If a piece of the extrusion breaks lose it is referred to as a sequestered fragment. If a disc herniation occurs into an adjacent vertebral body this is called an intravertebral herniation. Disc herniations are further classified as contained, uncontained, as well as by location, size, volume and content.
Disc Degeneration: Characteristic features of disc degeneration include disc dehydration (dessication), fibrosis, narrowing of the disc space, diffuse bulging of the disc and the development of annular tears. It also includes the development of bone spurs (osteophytes along the boney margin of the disc and thickening (sclerosis) of the vertebral endplates. Degeneration weakens the intervertebral disc and renders it more vulnerable to compromise with normal stress and strain and to injury. The term spondylosis defromans may be used to describe age-related disc changes. The termintervertebral osteochondrosis may be used to describe disc degeneration secondary to a pathologic (disease) process.
Disc Inflammation and Infection: This category of disc disorders includes infection,
infection-like inflammatory changes and inflammation due to a variety of conditions. The presence of inflammatory changes in the disc is often referred to as discitis. Infectious and inflammatory changes often extend into neighboring bone (vertebrae).
Disc Neoplasia: Primary cancer or metastatic cancer of disc tissues is referred to as disc neoplasia. It is further categorized by the type of neoplasia.
Discs with Structural (Morphological) Variants of Unknown Significance: This category includes discs that have structural abnormalities that cannot otherwise be classified into one or more of the other accepted categories of disc disorders.
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