Scoliosis nomenclature

Scoliosis is lateral curvature of the spine in the coronal (frontal) plane.

The apex (or apical vertebra) is the vertebra whose center is most laterally displaced from the central line.

Curves are named for the convex side (the side towards which the curve bows out to):

dextroscoliosis = convex to right, levoscoliosis = convex to left.

The degree of scoliosis may be measured using a number of methods. A commonly used measurement is the Cobb angle

Lippman-Cobb method: on an AP X-ray, the “end vertebrae” are identified at the top and bottom of the scoliotic curve and are defined as the vertebrae with the greatest angle relative to the horizontal plane. The levels are generally chosen based on the estimation of the person doing the measurement, and may vary between evaluators. Because of this and other measurement variations and errors, a Cobb angle change between X-rays of ≤ 5° is not consid- ered to be significant. One line is drawn tangent to the superior endplate of the superior “end vertebra,” and a second is drawn tangent to the inferior endplate of the inferior “end vertebra.” The Cobb angle is the angle between these 2 lines. This is easily measured using imaging software on computer monitors. On actual X-ray film a goniometer is used; if the lines meet too far away from the X- ray, measurement is facilitated by drawing right angles to both of these lines and measuring the angle between these secondary lines (which produces the same angle).

A non-structural curve can correct on side bending. A structural curve is not flexible. The major curve is the largest structural curve. A fractional curve is the curve below the major curve.

Scoliosis is measured using Cobb angles.

Curves are named for the convex side dextroscoliosis convex to right. Levoscoliosis convex to left.