What causes adult degenerative scoliosis?
Adult degenerative scoliosis can be a result of scoliosis from childhood. The curvature may increase during adulthood and become painful. Scoliosis that happens in childhood is usually idiopathic, meaning there is no known reason for it.
Any part of the spine can be affected by scoliosis including the cervical, thoracic, or lumbar vertebrae. Most often the lumbar spine is affected. The vertebrae curve to one side and may rotate, which makes the waist, hips, or shoulders appear uneven.
The most common cause of adult degenerative scoliosis is from degeneration, known as wear and tear. It usually occurs after the age of 40. In older women, it is often related to osteoporosis. Osteoporosis is the loss of calcium in the supporting bone. This makes the vertebrae weak.
In adult degenerative scoliosis, the spine loses its structural stability and becomes unbalanced. This imbalance of the spine causes changes in the way the forces of the spine are directed. The larger the scoliotic curve becomes, the faster these changes cause degeneration of the spine. This creates a vicious cycle where increasing deformity causes more imbalance, that in turn causes more deformity. While this process occurs very slowly, it usually continues to slowly progress until something is done to restore the balance in the spine.
When there is an S curve when viewing the spine from the front, the condition is called scoliosis. The scoliotic deformity may also affect the normal S curve that the spine has when viewed from the side. These curves are normal and required to maintain the proper balance of the spine. Many patients with scoliosis actually lose the normal curves of the spine.
Our body has a natural tendency to try to maintain a balance where the head is straight above the middle of the pelvis. If one leg is longer that the other, and the pelvis tilts, the spine will curve in the opposite direction to place the head above the center of the pelvis. If there is a curve in a portion of the spine, then the remainder of the spine will bend in the opposite direction to try and keep the head above the middle of the pelvis.
The scoliotic curve has a convex and concave side. The convex side is simply the outside of the curve where concave is the inside of the curve. The spine above and below the curve will tend to bend in the opposite direction in an attempt to balance the spine. Remember, the body will always try to place the head immediately above the middle of the pelvis. The concave side will tend to have more compression of the facet joints and possibly the nerve roots. This can lead to more pain from arthritis on the concave side of the curve and may lead to pain, weakness and numbness into the legs from the compressed nerve roots. These nerve changes are called radiculopathy.
In adult degenerative scoliosis, there is gradual narrowing of the discs that cushion between the vertebrae. The cartilage and joint surfaces of the facet joints in the spine can wear out, causing arthritis. This can cause back pain.
Stenosis is a term meaning narrowing. There are times when the canal for the spinal cord is narrowed. The openings for the nerve roots may also be narrowed. This will usually cause compression of the nerve structures. When the spinal cord or spinal nerves are compressed, pain, changes in feeling and/or motor function of the muscles can happen.
Sometimes spondylolisthesis occurs. This is slippage of one vertebra on the other. This can happen in adult degenerative scoliosis when the vertebrae do not stack on top of one another like they are supposed to. One vertebra may be shifted sideways or forward, not lining up as it should. The slippage is graded from I to IV, one being mild, IV often causing neurological symptoms.
In rare and severe cases, the chest may become deformed because of scoliosis. This may affect the lungs and heart. This can lead to breathing problems, fatigue, and even heart failure.
Degenerative scoliosis is more common the older we get. As our population ages, adult scoliosis will be even more common. It will be an increasing source of deformity, pain, and disability.