One of the common causes of low back pain is due to minor damage to the disc known as Internal Disc Disruption (IDD). It is believed that around 40% of low back pain is caused by IDD.
Damage to the disc can be caused by a number of factors from overload and injury to long term poor postural habits and the degenerative nature of the disc itself.
Any factor that creates undue load on the spine can lead to injury and back pain. Too much mechanical stress or dysfunction may occur due to repetitive strain of the spine leading to fatigue, one very large strain, or unexpected strain. Poor technique in physical activities or poor body mechanics may lead to disc
injury. Unexpected loading can result from falls, collisions or poor technique.
You will remember from the last blog that the discs are mainly avascular and the nucleus and inner 2/3 of the annulus have no nerves. The outer third of the disc does, however, contain tiny pain-carrying nerve fibres (nocioceptive C-fibres) that, when irritated, have the capacity to cause pain and disability.
When a tear of the annulus spreads to the outer third of the disc, these nerve endings (known as sino-vertebral nerve endings) are exposed to material leaking out from the nucleus of the disc which will lead to pain from the chemical irritation of these pain-carrying fibres.
Mechanical pain can occur when the functional abilities of the annulus are compromised. When the nuclear material invades the annulus, it will destroy annular collagen fibres. The mechanical forces spread across the remaining fibers and overwhelm the disc’s normal ability to support the weight of the body and the strong compression and rotation forces placed on the spine. The excessive strain transmitted to the highly nerve sensitive outer third of the disc results in mechanical pain signals on normal movements.
Tears can occur from the inner part of the disc outwards but also from the outer part in. there is also a relationship between a disc that has lost some of its water content and become increasingly brittle (part of the degenerative disc process) and disc tears
In a degenerative disc you can also get radial tears running circumferentially around the brittle annulus itself. These are known as concentric annular tears, or radial tears, and will weaken the disc and create an irritation of the nerve fibers within the annulus of the disc.
The symptoms of back pain due to disc disruption are of chronic duration and typically worse with any loading of the disc or activities that increase the intradiscal pressure. Such activities often include bending, lifting, sitting and, sometimes changes in posture.
This pain is not a result of disc compression upon the nerve root, which is the case in a disc herniation, but rather, it is due to the damage of the internal structure of the disc itself. The resulting changes to the nuclear material and internal radial fissures lead to a pain that does not usually radiate into either leg past the knee and there are not usually classic neurological findings. In other words, there is generally no weakness or sensory loss, no loss of deep tendon reflexes or root tension signs.
Most people who suffer back pain from IDD will obtain relief with time and conservative treatment. IDD can take up to 18 to 24 months to heal and patience is, obviously, an important factor here. The other important factor is to reclaim mobility as early in the healing process as possible, without exacerbating the pain. Conservative osteopathic approaches include gentle traction and mobilisation treatments and spinal stabilization training exercises.
Anti-inflammatory and analgesic medications will also aid in the early part of the healing process.
To get a visual sense of this process go across to http://www.bayareapainmedical.com/disruption.html and click on their animation