What Are Spinal Deformities?

Scoliosis is defined as abnormal lateral (to the side) curvature of the spine measuring greater than 10 degrees. When the body is viewed from behind, a normal spine appears straight (figure 1a). However, when a spine with a scoliosis is viewed from behind, a lateral, or side-to-side, curvature may be apparent (figure 1b). This gives the appearance of leaning to one side and should not be confused with poor posture.

A scoliotic curve may be functional or structural in nature. Functional curves may be positional. For example, if a person stands asymmetrically, with one knee bent, and the pelvis tilted downward, a curve will be present, but this will go away as soon as the knee is straightened and the pelvis is held parallel to the floor. Structural curves are those that have stiffness within them, such that they do not go away with changes of position. These therefore have much more significance than functional curves.

When the trunk is viewed from the side, the normal spine will demonstrate normal curves. The upper chest area has a normal roundback, or kyphosis, while in the lower spine there is a swayback, or lordosis (figure 2a). Increased roundback in the chest area is called hyperkyphosis, while increased swayback is termed hyperlordosis (figure 2b). Changes from normal on a side view frequently accompany scoliotic changes. The normal thoracic kyphosis is decreased with the most common form of scoliosis in adolescents.

Figure 1a

Figure 1b

Figure 2a

Figure 2b