By: Gema Sanchez, PT
As many as 85% of people are affected by low back pain at some point during their lives. Of the many causes of low back pain, intervertebral disc degeneration and disc herniation are among the most common. So, if you want to have a healthy spine and minimize low back pain, you need to have healthy discs.
What is an intervertebral disc?
The discs are partially movable joints that connect the bones of the spine (the vertebrae). The function of the disc is mechanical: it transfers loads, dissipates energy and helps joint mobility. It is composed of two parts: the nucleus pulposis in the center and the annulus fibrosis which encircles the nucleus. The nucleus is gelatinous, it has a high water content in a matrix which resists forces of compression. The annulus is composed of rings of fibrous cartilage surrounding the nucleus which resist the forces of rotation.. Most of the disc has a very poor blood supply so it relies on the squeezing and releasing of the spine through everyday motion to provide it with nutrition, much like squeezing soap though a sponge. To maintain health, the disc maintains a delicate balance of breaking down and rebuilding. This balance is easily disrupted by factors such as aging, mechanical loading, and environmental and genetic factors.
How is the disc damaged?
Disc degeneration is part of the natural process of aging but can also be caused by excessive and/or repetitive loading. Disc herniation, also known as a disc bulge, occurs when the annulus tears and the disc begins to change shape, sometimes leaving it’s normal confines and pressing on the spinal cord or nerves. Disc herniation can occur as a result of degeneration or from a sudden injury such as very heavy lifting or a car accident.
What can I do to keep my discs healthy?
- Don’t smoke. Smoking has been demonstrated to have a profound impact on disc degeneration and herniation. Smoking causes changes to the chemistry of the disc resulting in decreased cell production, disruption in cell architecture and disintegration of cells and matrix.
- Keep a healthy weight. Increased body mass increases the load on the disc, accelerating disc degeneration. There is also evidence to suggest that there may be a link between disc degeneration and the secretion of the peptide hormone leptin from adipose tissues. This hormone is a biomarker of obesity and is believed to promote the production of abnormal nucleus cells.
- Stay active, but don’t overdo it. Mechanical loading effects on the disc depend on how much of a load there is and how long it lasts. The normal pattern of unloading at night and loading during the day maintains the balance of breakdown and rebuilding in a healthy disc. If the disc does not get enough of a load, it begins to swell and lose structure. But continuous or excessive loading causes cell death and disc degeneration. So moderate loading is best: laboratory and clinical evidence suggests that moderate mechanical loading promotes effects which protect and repair the spine and may delay the development or progression of disc disease.
Can the disc heal?
Well, that depends on location. The nucleus and inner annulus does not have a blood supply, so it does not heal well. In fact, it is still uncertain if regeneration and repair of the nucleus or the inner annulus is even possible. But there is some research that suggests that releasing compression on a degenerated disc results in rehydration and chemical changes which indicate tissue recovery. In terms of the outer annulus, the news is better; it appears to demonstrate good healing potential. In animal models, the outer annulus has been shown to be able to resist pressure within the nucleus in as little as six weeks of healing. The outer annulus is different from the nucleus and inner annulus in several ways; it is anchored directly to bone, has some blood supply and shares similar cells and composition to tendons and ligaments. It has been shown that application of appropriate levels of tension along the lines of fiber orientation assists healing in tendons and may assist in reducing excessive scar formation following an injury. Since the outer annulus shares several important characteristics with tendon, we can apply these healing principles to the outer annulus to promote healing.
So exercise can help heal the disc?
We think so, but the exercise has to target each part of the disc separately and be progressed individually, depending on where you are in your healing process. We use rotation exercises to encourage healing of the annulus and modified compression-decompression exercises for the nucleus, starting with the right amount of force for where you are in your healing process and progressing as you improve.