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Average 4.2 of 41 Ratings
A 37-year-old male feels a "pop" in his low back while lifting a heavy object. Four weeks later he continues to have significant low back pain, with no complaints of symptoms in his leg. A T2-weighted MRI is shown in Figure A with a red arrow identifying abnormal signal intensity in an anatomic structure. What type of collagen is primarily responsible for the biological properties of this anatomic structure?
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The clinical presentation is consistent with an annular tear. The annulus fibrosis is composed of primarily type I collagen.
The intervertebral disk is made up of two major components. The outer structure is referred to as the annulus fibrosis. It is made up of water, proteoglycans and predominantly type I collagen. There is a high collagen/low proteoglycan ratio. The nucleus pulposus is the central portion of the disk. It is composed of water, proteoglycans, and predominantly type II collagen. It has a high compressive strength secondary to its low collagen/high proteoglycan ratio.
Biyani et al. review the pathophysiology of low back pain. They note that Type I and Type II collagens are found within the annulus fibrosis and nucleus pulposus respectively. Other collagen types, such as Type VI/IX are found in both components, whereas Type XII is found within the annulus only.
Boos et al. investigated age-related histologic changes in the human lumbar intervertebral disc. They report compromise of the intervertebral blood supply leads to the degeneration of the disk. This process starts in the second decade of life, specifically with tissue breakdown occurring in the nucleus pulposus.
Figure A is a T2-weighted MRI of the lumbar spine. The red arrow demonstrates an area of signal intensity consistent with an annular tear. Illustration A is a drawing of an intervertebral disk, demonstrating an outer annulus fibrosis and an inner nucleus pulposus.
Answers 2, 3, 4, 5: The annulus fibrosis and nucleus pulposus are composed of Type I and Type II collagen respectively. There are small amounts of Type V in the annulus fibrosis and small amounts of Type XI in the nucleus pulposus
Biyani A, Andersson GB
J Am Acad Orthop Surg. 2004 Mar-Apr;12(2):106-15. PMID: 15089084 (Link to Abstract)
Biyani, JAAOS 2004
Boos N, Weissbach S, Rohrbach H, Weiler C, Spratt KF, Nerlich AG
Spine. 2002 Dec;27(23):2631-44. PMID: 12461389 (Link to Abstract)
Boos, SPINE 2002
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Average 3.0 of 13 Ratings
Which of the following statements is true with regard to the aging process of the intervertebral disc along the endplate?
Water content increases with age
Proteoglycans increase with age
Degradative enzyme activity decreases with age
pH increase with age
There is a conversion to fibrocartilage
Disc aging leads to an overall loss of water content and conversion to fibrocartilage.
The intervertebral disc allows spinal motion and provides stability. In addition, it is responsible for 25% of spinal column height. It consists of an outer annulus, with a high concentration of Type I collagen, and an inner nucleus pulposus, with a high concentration in Type II collagen. With aging there is degeneration of the disc that may alter the function as well.
Boos et al. investigated age-related temporospatial histologic changes in human lumbar intervertebral disc, and developed a practicable and reliable classification system for age-related histologic disc alteration. They noted clear histologic evidence for the detrimental effect of a diminished blood supply on the endplate, resulting in tissue breakdown beginning in the nucleus pulposus and starting in the second life decade. They were able to create a classification system that showed significant correlation with age and macroscopic grade of degeneration.
Roberts et al. wrote a comprehensive review of vertebral disc histology and pathology. They explain that with increasing age, water is lost from the matrix of the disc, and the proteoglycan content also changes and diminishes. The disc, particularly the nucleus, becomes less gelatinous and more fibrous. They conclude that a change in the morphology of the tissue is likely to alter the physiologic and mechanical functioning of the disc.
Illustration A shows an intervertebral disc and its primary components. The nucleus pulposis (primarily type II collagen) is found centrally in the disc surrounded by the annulus fibrosus (primarily type I collagen). Illustration B shows a T2-weighted lumbar MRI pointing out the normal disks with higher water content (bright on T2) and degenerated disks with less water content (dark on T2).
Answer 1: Intervertebral water content decreases with age.
Answer 2: Intervertebral proteoglycans decreases with age.
Answer 3: Degradative enzyme activity increases with age.
Answer 4: pH decreases with age
Roberts S, Evans H, Trivedi J, Menage J
J Bone Joint Surg Am. 2006 Apr;88 Suppl 2:10-4. PMID: 16595436 (Link to Abstract)
Roberts, JBJS 2006
Average 3.0 of 18 Ratings
Which of the following are progressive changes seen with aging of the intervertebral disc?
Increase in water content
Increase in large aggregated proteoglycans
An increased keratan sulfate to chondroitin sulfate ratio
A decrease in degradative enzyme activity
An increase in nutritional transport
With aging of the intervertebral disc there is an increase in the keratan sulfate to chondroitin sulfate ratio.
The objective of this question is to focus on the basic science of an aging intervertebral disc. Histologic assessments clearly support this notion by the coincidental disappearance of blood vessels from the endplate and the increase in matrix breakdown, as evidenced by the occurrence of cartilage cracks, microfractures in the end-plate, and tear and cleft formation in the nucleus pulposus (NP).
Kang et al. showed that while normal intervertebral disc cells are biologically active, cells of the herniated disc are more active. Additionally, interleukin-1 beta will increase their production of of matrix metalloproteinases, nitric oxide, interleukin-6, and prostaglandin E2.
Boos et al. in an article describing histology of age-related changes in the intervertebral disc found that degeneration involves: 1) declining disc nutrition, 2) loss of proteoglycan organization and concentration, 3) decrease in water content, 4) a decline in cell numerical density and synthetic activity, 5) increased degradative enzyme activity relative to matrix synthesis.
Illustration A is a diagram of the aging of intervertebral discs.
Answer 1: With aging there is a decrease in water content in the intervertebral disc.
Answer 2: With aging there is a decrease in large aggregated proteoglycans associated with the increase in degradative enzyme activity.
Answer 4: With aging there is a increase in degradative enzyme activity.
Answer 5: With aging there is a decrease in nutritional transport.
Kang JD, Stefanovic-Racic M, McIntyre LA, Georgescu HI, Evans CH
Spine. 1997 May;22(10):1065-73. PMID: 9160463 (Link to Abstract)
Kang, SPINE 1997
Average 4.0 of 12 Ratings
Recent studies have shown that cells of the intervertebral discs are biologically responsive and increase their production of matrix metalloproteinases, nitric oxide, interleukin-6, and prostaglandin E2 when stimulated by what molecule
transforming growth factor-beta
receptor activator of nuclear factor-kB ligand (RANKL)
parathyroid hormone (PTH)
Kang et al showed that "cells of the intervertebral discs are biologically responsive and increase their production of matrix metalloproteinases, nitric oxide, interleukin-6, and prostaglandin E2 when stimulated by interleukin-1 beta. The effect is more dramatic in normal, nondegenerated discs where spontaneous synthesis of these mediators is low. Nevertheless, cells of the herniated degenerated discs where spontaneous production was high were still capable of further increasing their synthesis of several of these biochemical agents in response to interleukin-1 beta. Endogenously produced nitric oxide appears to have a strong inhibitory effect on the production of interleukin-6, which suggests that autocrine mechanisms play an important role in the regulation of disc cell metabolism." OPG acts as a decoy receptor in the RANK-RANKL signaling system inhibiting osteoclast formation. RANKL and PTH act in the signalling pathway to activate osteoclasts.
Average 1.0 of 62 Ratings
Which of the following processes is involved in age-related intervertebral disc degeneration?
increased cell number in the nucleus pulposus
increased matrix synthesis
increased disc height
increased degradative enzyme activity
increased chondrotin sulfate
As aging occurs, increased degradative enzyme activity is seen in the intervertebral disk.
The aging process leads to a loss of water and fibrocartilage development within the intervertebral disk. There is an increase in enzymatic degradation activity, lactate levels and the keratin sulfate to chondroitin sulfate ratio. There is a decrease in water content, pH, absolute number of viable cells, and nutritional transportation.
Boos et al. histologically evaluated the intervertebral disc to ascertain age related changes. They noted declining disc nutrition, loss of proteoglycan organization, diminished cellular density and increased degradative enzyme activity. This cascade likely results from vascular insult to the disk in the second decade of life.
Illustration A shows a sagittal T2-weighted MRI sequence with degenerative changes in the spine. Limited signal within the disk is indicative of dehydration. Illustration B is a schematic demonstrating how disk herniations may result as the disk ages.
Answers 1, 2: As aging occurs, there are a decreased number of cells in the nucleus pulposus and decreased matrix synthesis.
Answer 3: There is decreased disc height with aging.
Answer 5: As the disk ages, there is a decrease in the amount of chondroitin sulfate and an increase in the amount of keratin sulfate.
Average 3.0 of 16 Ratings