A spinal disc is a structure that sits between 2 spinal vertebrae and allows for a certain amount of movement of the vertebrae relative to one another, but limits excessive movement. The discs also serve as a shock absorbing cushion to protect the vertebrae, brain and nerves.
The discs are made of many layers of strong, cross hatched fibres surrounding a softer inner gel.
When a disc “slips” it gives the idea that it just moved out of place a bit and all that is needed is a careful manipulation and put it “back in.”
Discs support the weight of the body above and this places a certain amount of pressure on the disc structure. The disc is designed to handle this pressure and does so very well under normal circumstances. However, the outer fibres of the disc may become torn, fissured or cracked. If disc wall is sufficiently weakened, the pressure on the disc squashes the inner gel and pushes it out through the damaged area.
Unfortunately , the “slipped disc” terminology leads to a misunderstanding of what really happens and likely a misconception of what it takes to heal this type of an injury.
The disc wall may only be weakened a bit and distends out mildly – called a disc bulge.
The disc wall may be more severely damaged and the inner gel can push right out, called a protrusion or herniation.
When a lumbar disc protrudes the spinal nerves may become irritated causing the feeling of pain going down the leg (sciatica) and sometimes even into the foot. There may also be numbness down the leg or a sensation of pins and needles. Sometimes the leg or foot may seem to lose strength or even give way.
Discs in the neck can also protrude causing similar problems in the arms and hands instead of the legs and feet.
Why do disc fibres become torn and allow the bulge/protrusion to occur?
Severe impacts may cause a rupture of the disc fibres but often there is no recent severe injury to account for the disc damage.
Instead it appears that there is a steady decline or degeneration of the disc that eventually leads to the weakness in the disc wall. Approx 20% of teenagers already have early signs of disc degeneration.
When there is abnormal weight bearing causing extra strain on the discs, restricted motion of the spinal joint and reduced blood flow to the area, small tears to the disc fibres occur and while these tears tend to heal up, often the repaired tissue is not as good as the original – fibrosis. Many small tears (repetitive strains) lead to a considerably weakened disc which may then give way and protrude.
So what causes the abnormal weight bearing, restricted joint motion and restricted local circulation?
To answer this question, a basic idea of how muscles work is appropriate. Movement occurs in our body when a signal from the brain (central part of the nervous system) tells a muscle to shorten or contract. Muscles are connected to 2 or more bones across one or more joints.
For example, in the diagram to the right, the biceps connects to the upper arm bone and to the forearm bone passing across the elbow joint. When the biceps muscle contracts, it pulls the forearm up. When the biceps is relaxed, the forearm hangs down. This is a simple movement.
With the spine it is much more complex. There are several layers of muscles that affect the spine and many joints from the skull to the pelvis. So movements of the neck, back and pelvic area are complex combinations of muscle contractions. Fortunately, we don’t have to consciously control these contractions. We just decide to move and appropriate signals from the nervous system cause the muscles to contract in the right way at the right time to make the movement happen.
This is all good and well. However, as we go through life, injuries, stressful experiences and toxic chemicals affect the nervous system causing tension to build up. This causes many muscles to become excessively tense and often in an unbalanced way. This muscle tension pulls abnormally and unevenly on the spinal joints causing stiffness, abnormal alignment, distorted posture and abnormal weight bearing. The excess muscle tension also limits normal joint movement and may even make some segments of the spine appear to be out of line with other spinal segments. In these tense and distorted tissues, the localised flow of blood may be reduced.
The nervous system control of the muscle contractions may also be affected so the muscle contractions may not occur in the right way at the right time. Serious problems may result from this effect alone.
In summary , a slipped disc is actually a disc with a degenerated and torn or damaged wall that allows the inner gel to push out and aggravate other structures.
Nervous system tension affects the muscles which affects the spine including the joints and the discs and over time may lead to disc degeneration as described above.
Therefore, optimising the body’s ability to heal and recover from disc problems is likely to require a reduction of nervous system tension so muscles relax and balance, spinal stiffness and distortion reduce and local blood flow is normalised.
This is what we do at the Better Life Chiropractic Center in Dandenong utilising Network Chiropractic. Please see other pages for more info on Network.
If you have back or neck pain, or sciatica or known disc problems and would like help that is drug and surgery free, please phone 9793 3755.