A healthy disc is tough, resilient and resembles "gristle". As a disc degenerates it looses its toughness and assumes the consistency of soft "crab meat". This is the process of degeneration. As degeneration progresses the structural integrity of not just the disc but also that of the vertebral segment is compromised. This situation leads to segmental "dysfunction" much like "shimmy" in a car body. This "shimmy" directs stress to the zygoapophyseal joints (facet joints) causing them to also degenerate. Disc degeneration is easily recognized in post mortem tissue but the magnetic resonance imaging (MRI) technique is a particularly sensitive means of showing this. The reason for this is that "normal" discs are about 85% water. As discs degenerate they loose their water content. An MRI scan is actually a scan of hydrogen ions in the body. Since almost all hydrogen ions are found in body water (H2O) a MRI is basically a very sensitive "water content" scan of all body tissues.

This lateral MRI scan shows a degenerated L4-5 level lumbar disc which has herniated (yellow dot). The radiologist has drawn the yellow lines to indicate the area of disc herniation. In this view the discs above and below have greater water content (less degeneration) and are shown to be lighter in color. A degenerated disc is more likely to herniate than one possessing a normal structure. Intervertebral discs are one of only two body structures in adult life which do not have their own blood supply. The other one is the cornea of the eye. The cornea obtains its nutrition from tears while the disc obtains its nutrition from the diffusion of nutrient solutes across the porous endplates of the adjacent vertebrae. This flow can be enhanced by "pumping" activities (types of exercise) and by decreasing intradiscal tension (by segmental traction or distraction). In the case of individuals born with abnormal endplates (i.e. juvenile discogenic disease) the challenge to maintain healthy discs is greater and the liabilities of poisoning discal cells (i.e. smoking) is greater.

The spine model to the left is for reference. In the middle image normal discs are present. In the image to the right the upper disc shows degenerative change and a bulge in the annulus.

Disc Degeneration versus Degenerated Tires

Photo of an upside-down Ford Explorer following failure of the tire casing. In many ways the simile between degenerated discs and degenerated tires is valid. In order for a human being to be successful for long-term (about 80 years) ambulation on a high gravity planet the individual has to have been careful in parenteral selection so that their spinal column genetic makeup will be adequate to deal with the insults and injuries along the way. If initial fabrication of the spine is flawed incapacitation and disability will result.

Tires, if sound, can be recapped. Spines only continue to be worn down by the daily insults of life and occupation, occasional traumas, and the process of aging. Genome testing to determine spine liabilities early in life will be the future equivalent of tire testing before use. Its a shame we don't have this now because because valid self-administered spine health maintenance programs presently exist.

Tires are stressed when underinflated and run at high speeds in high temperature environments. In the same way human spines are stressed by labor intensive jobs as well as occupations such as trucking where compressional loading and vibratory factors conspire to injure discs. The simile with tires ends with the observation that humans can actually, on a daily basis, perform health maintenance programs capable of enhancing and improving spine nutrition and function whereas tires can only become more run down over the passage of time.

How Does Disc Herniation Start?

Unless due to acute trauma a typical disc herniation begins with an unhappy disc. The circumstances that promote this state of affairs is, as can be seen, are usually multiple leading to a loss of disc integrity. Once degeneration exists it usually doesn't take much for a disc herniation to start. Very often the first step in this process is a twist "injury" producing a tear in the disc annulus.

In this lateral MRI image the red dot is to the right of a degenerated disc showing the beginning of a herniating disc. At this stage the discal bulge is usually described as a "annular tear". In this case there is a small are of high intensity shown at the bottom of the tear. This is called a "high intensity zone" and refers to inflammatory fluid in a discal tear. This "HIZ" type of tear has been correlated with a high incidence of associated back pain and represents one of the very few MRI findings which can be directly related to back pain.

In this axial MRI scan from the same patient the red dot is exactly placed over the "high intensity zone" annular tear which, if seen from the side, appears as a white dot.

As the disc degenerates segmental dysfunction occurs. One result of this is continuing stress and reactive degeneration of the zygoapophyseal (facet joints). This axial view MRI scan shows just such a circumstance where the segmental dysfunction has produced advanced degenerative change in the facet joints. The white material in the joints is reactive effusion. In essence these facet joints have become functionally incompetent and the entire vertebral segment is now dysfunctional. This particular patient is developing a degenerative spondylolisthesis (L-spondylo= vertebrae; L-listhesis= slip).

Disclaimer On Disc Degeneration

Before the web traveler goes any further in this discussion about disc degeneration and herniation a disclaimer is necessary and is here-to-fore presented:

Mother Nature is the very best healer and, even though scientific data does not exist on this subject, it is clear that in the vast majority of cases degenerated discs are absorbed, the interspace narrows, osteophytes are formed, and a "restabilization" occurs spontaneously. Often the individual is aware only of a gradual reduction in body height, taking place over a period of years. A truism is: "if you are good to Mother Nature, she will be good to you".

Courtesy of Wolfgang Rauchning

Courtesy of William Kirkaldy-Willis

The images to the left are actual anatomic examples of chronic degenerative changes where the process of healing and re-stabilization is occurring. The ability of the spinal nerves to gradually acclimate to this process and maintain apparently "normal" function is truly amazing.

Why Is There Back Pain?

In the September 2000 Issue of the Oprah Magazine there is an article entitled "The Real Source of Your Back Pain" written by Emma F. Segal quoting Art Brownstein M.D. In answer to the question "What causes most back problems?", is the reply "Muscle strains and sprains". Another quote is the response "It is a common misconception that back pain starts with a disc problem". These statements are poor responses and misleading to the public.

The most significant pain related to the back is when the spinal cord or spinal nerves are involved. When associated with progressive neurologic problems surgery is often required, sometimes on an urgent basis. This represents a very uncommon situation. The common situation is frustrating persistent low back pain affecting the individual's quality of life and ability to function.

The surface of the brain given over to representing the back, in comparison to areas such as fingers, tongue, etc.) is remarkably small. That is part of the reason that back pain is so non-specific and so poorly localized. There is no question but that one can "strain or sprain" the ligamentous or muscular components of the spine but most back pain, spasm, and incapacitation are secondary to degenerative changes in the intervertebral disc reflecting congenital abnormalities and acquired insults and injuries. Because "screening" MRIs are not routinely performed on asymptomatic individuals a valid data base on this subject simply does not exist. Quite frankly it's hard enough, with managed care, to obtain MRIs on patients disabled by severe back pain. As quality MRI data on individuals with back pain is carefully analyzed the presence of early degenerative changes is better appreciated. As data on the children of adults identified with conditions such as "juvenile discogenic disease" becomes available through "screening MRIs" we can now, for the first time, better appreciate the presence of "time bombs" in the spine and initiate rational therapeutic and preventive programs in young individuals belonging to "high risk" families..

A complete MRI is an expensive proposition typically costing $1,000-1,2000 in the United States. A "screening MRI" costs a great deal less (usually $350-500). All adults in the population have some degree of disc degeneration and it is therefore essential that these studies be reported by clinicians who know what to look for. Most radiologic MRI reports, in the Burton Experience, only demonstrate how little is known regarding radiologic diagnosis. Given that so little is really known regarding the differential diagnosis of disc degeneration and its role in initiating segmental disease it is not surprising that early identification and initiation of self-administered preventive programs, which may very well represent the very best investment which can be made in the future health and productivity of the population is presently a rare phenomenon.