Scoliosis - Introduction

Other abnormalities of the spine that may occur alone or in combination with scoliosis include hyperkyphosis (an abnormal exaggeration in the backward rounding of the upper spine) and hyperlordosis (an exaggerated forward curving of the lower spine, also called swayback).

Click the icon to see an image of kyphosis.

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Defining Scoliosis by Its Location

The location of a structural curve is defined by the location of the apical vertebra. This is bone at the highest point (the apex) in the spinal hump. This particular vertebra also undergoes the most severe rotation during the disease process.

Defining Scoliosis by Its Direction

The direction of the curve in structural scoliosis is determined by whether the convex (rounded) side of the curve bends to the right or left. For example, a doctor will diagnose a patient as having right thoracic scoliosis if the apical vertebra is in the thoracic (upper back) region of the spine and the curve bends to the right.

Defining Scoliosis by Its Magnitude

The magnitude of the curve is determined by taking measurements of the length and angle of the curve on an x-ray view.

The Spine

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:

The cervical (C) vertebrae are the seven spinal bones that support the neck.
The thoracic (T) vertebrae are the twelve spinal bones that connect to the rib cage.
The lumbar (L) vertebrae are the five 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 bone 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 two to four 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 (its kyphosis) while the lower back has a reverse inward curve (its lordosis).

The Disks. Vertebrae in the spinal column are separated from each other by small cushions of cartilage known as intervertebral discs. Inside each disk is a jelly-like substance called the nucleus pulposus, which is surrounded by a tough, fibrous ring called the annulus. The disk is 80% water. This structure makes the disk both elastic and strong. The disks have no blood supply of their own, however, but rely on nearby blood vessels to keep them nourished.

Processes. Each vertebra in the spine has a number of bony projections, known as processes. The spinal 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).

Spinal Canal. Each vertebra and its processes surround and protect an arch-shaped central opening. These arches, aligned to run down the spine, form the spinal canal, which encloses the spinal cord, the central trunk of nerves that connects the brain with the rest of the body.