As we age, our the structures that provide protection and stability for our spine slowly degenerate, and our body is no longer able to restore and repair these structures at the same rate in which they break down. The structures that provide cushion and shock absorption for our spine as it bends, twists, and is compressed downwards include the facet joints and the intervertebral discs. The discs provide the spine with cushions between the vertebral bodies at the front of the spine, and the facet joints provide support and prevent friction among the facets at the back of the spine. Here, we will learn more about how these supportive structures break down, and how their pathology affect the other structures of the spine.
The intervertebral discs. The intervertebral discs have a shape similar to a hockey puck, and separate the vertebral bodies to separate the bones from wearing down by rubbing together. When these discs are healthy, their membranes remain healthy and intact, and maintain a space between the vertebral bones that is big enough for the nerve roots that exit the spine do so without being squeezed. The intervertebral discs have a fibrous, continuous outer shell known as the discus annulus, and a gelatinous shell known as the nucleus pulposus. This inner gel-like nucleus has a high water content, and it gives the disc the ability to change shape to absorb increases in loads the spine must take on as we stand and walk, and put extra weight on it. The disc overall has enough flexibility to bulge downwards and outwards, but also enough rigidity to maintain its basic shape so that it does not collapse completely or fail to protect the spine from injury.
After our body and spine reaches maturity, the water content of the intervertebral discs' nuclei begins to decrease. Also, the individual fibers, which compose the many layers of the annulus begin to wear out. The net effect of these two changes is a reduced height of the discs and the propensity of the outer wall of the discs to become threadbare (worn out). these discs have little ability to regenerate themselves, and annulus may sustain tears.
These discs often develop concentric tears, which start at the nucleus and work their way towards the shell's outer edge. Because the back sections of the discs are congenitally weaker than the front sections, this outer shell is more likely to tear at the back of the disc rather than the front. The person with the degenerative disc disease may also experience back pain due to the fibers at the front of the disc eventually becoming torn and herniated.
The facet joints, as well as other weight-bearing joints of the body, may degenerate as well, as they lose their volume of cartilage, and lose their ability to lubricate joints. This spine disease may also occur in the facet joints, and the result may include wear and tear of the joints.
Anatomical changes may also occur in the spinal ligaments that stabilize the spine. Due to the aging process, the ligaments may begin to loosen, become lax, and lose some of their tensile strength. Loosening of the ligaments may lead to wear and tear of the facet joints.