Degenerative disc disease (DDD) is a condition in which the discs, or fluid filled sacs, that sit between each vertebrae of the spinal column deteriorate over time. The purpose of these discs is two-fold--the jelly-like center provides shock absorbency as the vertebrae move atop one another, and the cartilaginous outer ring provides vertical lift so that the nerves that come off of the spinal cord can travel freely to the rest of the body. A deteriorating disc causes pain--most commonly of the neck and low back--as well as narrowing of the spinal column and osteoarthritis.
Aging
Aging as a cause of DDD is the culmination of years upon years of use, also known as wear and tear. According to Cedars-Sinai Hospital, normal wear and tear over a 20 to 30 year period causes small tears of the disc cartilage in nearly everyone, but does not translate into pain for every aging person. The discs do not receive a direct blood supply like other tissues in the body and, the wear and tear can accumulate to the point that degeneration will set in. This causes altered function, instability and pain in some people.
Injury/Trauma
A blunt or acute injury to the back can lead to a tremendous tear in one or more disc in an instant. Ceders-Sinai Hospital notes that the effects of a direct trauma can cause swelling, soreness and instability, promoting further deterioration and interfering with any potential healing in the area. Injuries of this magnitude can occur secondary to sports injuries or as a result of slip-and-fall accidents. Repetitive injury, similarly to aging, occurs over a longer period of time and can expedite the damage caused by the aging process. In particularly susceptible individuals, repetitive bending, twisting, lifting and even the constant vibration from driving as an occupation, can induce DDD.
Genetics
Although the aging process and repetitive injury of occupation consistently results in degenerative disc changes, it does not cause pain and altered function in all people. Scientists are currently looking into whether genetics may play a part in who suffers from DDD. The vast difference in the subjective responses to the changes of DDD has been linked to a number of genetic variables and expressions. A 2002 Annuals of Medicine journal article lists genetic imbalances between enzymes that break down disc cartilage versus those that inhibit this action, variations in other markers of cartilage function and differences the body’s use of vitamin D as genetic factors that may dictate an individual's experience with DDD.
Dehydration
The center portion of the disc is filled with fluid. Adequate hydration of this sac determines its ability to be plump and absorb the shock of movement and small trauma. Without proper nutrition, the discs can become flat and dry. Chiropractor Kenneth Erickson notes that decreased hydration of the discs is the most common finding on an MRI when diagnosing degenerative disc disease. Dr. Erickson notes that dehydration occurs when less fluid is pulled into the disc than is squeezed out with the compressions of movement.
Smoking
Nicotine, the main ingredient in cigarettes, is implicated as a promoter of DDD, especially when combined with other risk factors and causes. The effects of nicotine on the nucleus pulposus, or the fluid -filled sac at the center of the disc, were published in a 2004 "Spine" article. Researchers concluded that nicotine starved the discs of adequate nutrients and oxygenation, instigated the dehydration of the disc and inhibited normal cell growth and reproduction.
Immune System
The immune system is a new area of study in the etiology of degenerative disc disease. Besides the contribution that genetics plays into the unequal distribution of DDD among aging or similarly injured people, the inflammatory state of the body appears to also selectively promote deterioration. Rheumatologist Dr. Mark Borigini writes that a particular inflammatory chemical, IL-17, has been specifically isolated in approximately 70% of tissue samples from DDD sufferers but is rarely found in normal tissue.
References
- Cedars-Sinai Hospital: Degenerative Disc Disease
- "Annals of Medicine"; Genetic Risk Factors for Lumbar Disc Disease
- Degenerative Disc Disease
- "Spine"; Effect of nicotine on spinal disc cells: a cellular mechanism for disc degeneration
- "Psychology Today"; Maybe Not Just Degenerative Disc Disease: The Immune System and Low Back Pain”
