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Scoliosis

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of scoliosis.

Introduction

Scoliosis is the abnormal curvature of the spine. While the normal spine has gentle natural curves that round the shoulders and make the lower back curve inward, scoliosis typically involves a three-dimensional deformity of the spinal column and rib cage. To varying degrees, the spine curves from side-to-side, and some of the spinal bones may rotate slightly, making the hips or shoulders appear uneven. It may develop in the following way:

• As a single primary side-to-side curve (resembling the letter C), or
• As two curves (a primary curve along with a compensating secondary curve that forms an S shape).

Scoliosis most commonly develops in the area between the upper back (the thoracic area) and lower back ( lumbar area). It may also occur only in the upper or lower back. The doctor attempts to define scoliosis by the following characteristics:

• The shape of the curve
• Its location
• Its direction
• Its magnitude
• Its causes, if possible

The severity of scoliosis is determined by the extent of the spinal curvature and the angle of the trunk rotation (ATR) and is usually measured in degrees. Curves of less than 20 degrees are considered mild and account for 80% of scoliosis cases. Curves that progress beyond 20% require medical attention. Such attention, however, usually involves periodic monitoring to make sure the condition is not becoming worse.

Scoliosis affects approximately 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 to 15 years. About 10% of the adolescent population has some degree of scoliosis, but less than 1% develops scoliosis that requires treatment. The condition also tends to run in families. Among persons with relatives that have scoliosis, about 20% develop the condition.

Among adults, previous reports have indicated a prevalence of scoliosis of up to 32%. But a recent study of 75 healthy adults aged 60 years and older with no known history of scoliosis or prior spine surgery suggested a rate of 68%. However, scoliosis was not linked to physical or social impairment in this population.

Defining Scoliosis by the Shape of the Curve

Scoliosis is often categorized by the shape of the curve, usually as either structural or nonstructural .

• Structural scoliosis. In addition to the spine curving from side to side, the vertebrae rotate, twisting the spine. As it twists, one side of the rib cage is pushed outward so that the spaces between the ribs widen and the shoulder blade protrudes (producing the rib-cage deformity , or hump). The other half of the rib cage is twisted inward, compressing the ribs.
• Nonstructural scoliosis. The curve does not twist but is a simple side-to-side curve.

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).

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: C ervical (C) vertebrae are the seven 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 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 ( 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 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, 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 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.

• Review Date: 4/19/2006
• Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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