Scoliosis affects about 2 - 3% of the population (about 6 million people in the United States). It can occur in adults, but is more commonly diagnosed for the first time in children aged 10 - 15 years. About 10% of adolescents have some degree of scoliosis, but less than 1% of them develop scoliosis that requires treatment. The condition also tends to run in families. Among persons with relatives who have scoliosis, about 20% develop the condition.
Scoliosis that is not linked to any physical impairment, as well as scoliosis linked to a number of spine problems, may be seen in the adult population as well.
Vertebrae. The spine is a column of small bones, or vertebrae, that support the entire upper body. The column is grouped into three sections of vertebrae:
- Cervical (C) vertebrae are the 7 spinal bones that support the neck.
- Thoracic (T) vertebrae are the 12 spinal bones that connect to the rib cage.
- Lumbar (L) vertebrae are the 5 lowest and largest bones of the spinal column. Most of the body's weight and stress falls on the lumbar vertebrae.
Each vertebra can be designated by using a letter and number; the letter reflects the region (C=cervical, T=thoracic, and L=lumbar), and the number signifies its location within that region. For example, C4 is the fourth vertebra down in the cervical region, and T8 is the eighth thoracic vertebra.
Below the lumbar region is the sacrum, a shield-shaped bony structure that connects with the pelvis at the sacroiliac joints. At the end of the sacrum are 2 - 4 tiny, partially fused vertebrae known as the coccyx or "tail bone."
The Spinal Column and its Curves. Altogether, the vertebrae form the spinal column. In the upper trunk the column normally has a gentle outward curve (kyphosis) while the lower back has a reverse inward curve (lordosis).
The Disks. Vertebrae in the spinal column are separated from each other by small cushions of cartilage known as intervertebral disks. Inside each disk is a jelly-like substance called the nucleus pulposus, which is surrounded by a tough, fibrous ring called the annulus fibrosis. The disk is 80% water. This structure makes the disk both elastic and strong. The disks have no blood supply of their own, relying instead on nearby blood vessels to keep them nourished.
Processes. Each vertebra in the spine has a number of bony projections, known as processes. The spinous and transverse processes attach to the muscles in the back and act like little levers, allowing the spine to twist or bend. The particular processes form the joints between the vertebrae themselves, meeting together and interlocking at the zygapophysial joints (more commonly known as facet or z joints).
Review Date: 04/06/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.