Scoliosis - Introduction

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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 a 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).

Click the icon to see an image of kyphosis.

Defining Scoliosis by Its Location

The location of a structural curve is defined by the location of the apical vertebra. This is the 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.

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.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).