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Herniated Discs

Disc Herniation

The spine is made up of a continuous series of segments known as vertebrae. Each vertebrae is separated by what is known as the intervertebral disc, which is made up of a firmly enclosed fluid filled “shock absorber” within which is a small gelatinous substance called the Nucleus pulpous. This is approximately 15% of the size of the whole disc.

As the complete spine has four natural curves through evolution, biomechanics explain different degrees of stress along different areas of the spine. As the vertebrae are designed in different ways as they progress down the spine, and also become larger, the nucleus pulpous also becomes closer to the back of the intervertebral disc. The low back known as the lumbar region thus have larger vertebrae than those in the neck and also have the nucleus more backward.

Also along the entire length of the spine at the front and back are strongly attached ligaments: the anterior (front) and posterior (back) longitudinal ligaments. The posterior ligaments are attached more strongly to the discs than to the vertebrae and also get wider as they descend down the spine. The anterior ligaments present in an opposite way, they are narrower as they descend and are more strongly attached to the vertebras.

Disc herniation occurs when the nucleus pulpous is pushed to the wall of the disc forcing the disc out of its space, due to pressures from body weight being transferred through the spine leading to shearing forces and strain from these movements to the spine. This is in a similar way to squeezing one end of a sponge to see it push out at the opposite end. As the vertebrae are larger in the lower back with a weighted nucleus resting more backwards, herniations are more common in this low back region. However due to the strong attachments of the posterior longitudinal ligaments the disc is unable to protrude directly backwards and therefore bulge backwards but towards the sides (poster lateral).
This area is sensitive and tightly packed as the peripheral nerves (nerves that supply skeletal muscles and joints) pass through this region also, leaving the spinal cord (protected within the vertebra) to their corresponding area of muscle and/or joint.

Disc herniations are a painful episode especially when they may apply pressure to the nerves, which may then present symptoms to the lower limbs as well as the low back.

Age

Disc changes are inevitable with aging. With increasing maturity the disc begin to reduce their elastic properties and also the ability to determine the exact boundaries between the nucleuses within the disc. As the absorbing qualities of the disc are reduced due to reduction in elasticity the outer borders of the discs become firmer and the liquid (water) content of the disc is reduced to about 70%. Hence the markedly low incidence rate of herniations in elderly people may be explained by these changes. The age of onset ranges usually from 20 to 50 years.

Smoking

Nicotine in tobacco, acts directly on the heart, blood vessels, digestive tract, kidneys and the nervous system.
Numerous studies have addressed the relationship between disc degeneration and smoking. Causative factors that have been suggested include reduction in blood supply to the heart and other organs as well as the spine, or that smokers may live more sedentary lives, or cough more. After quitting smoking, the increased risk of disc herniation still remains for some time.

Obesity

Obesity in a patient plays a causal role in back pain and disc degeneration. Obese people may lead less active lives without regular exercise to strengthen the heart and its blood supply to the body, and spine. With an ‘inactive’ spine weakened by increasing pressures of the weight of the body it has to support, degeneration is inevitable and herniations more susceptible.

Occupation

Some occupations and sporting activities involve heavy workloads with extremes of bending and twisting or prolonged standing or sitting, which are important factors for disc damage. A spine is vulnerable during these activities and pressures of heavy workloads put undue stresses through the intervertebral disc, which then cannot cope leading to disc degeneration (wear and tear), herniations (protrusions beyond their boundaries), and tears of the outer wall of the discs.
Problems may be exacerbated if lifting methods are incorrect, or if bending and lifting are undertaken in awkward positions. Therefore correct lifting techniques are important (back straight and knees bent, squatting to initiate a low level lift). Correct lifting techniques avoid leaving the spine in a prone position for injury and damage. Improper lifting techniques are perhaps the most frequent cause of back injury.

Sedentary Living

The spine requires movement and exercise at all stages of life to maintain function, therefore a sedentary occupation may be an increased hazard for disc degeneration. Prolonged sitting may cause increased pressure on the disc and therefore enhanced degeneration. Nutrition of the normal disc is supported and provided by spinal joint motion and the action of their surrounding muscles. Disc nutrition could become disturbed due to a lack of exercise resulting in a loss of these normal forces, leading to degenerative changes.

Health Dimensions ©2004