Scoliosis is defined as an abnormal, lateral curvature of the spine. This spinal deviation includes a rotational component, meaning the vertebrae also twist, making the condition complex. The standard for naming these curves is precise, and it directly addresses whether the name is based on the convex or concave side of the spinal bend.
Defining the Curve and Naming Convention
Every spinal curve has two distinct sides: the convex side and the concave side. The convex side is the outer, rounded part of the curve. Conversely, the concave side is the inner, hollowed-out portion of the curve. The technical naming convention for scoliosis curves is based definitively on the side of the convexity.
The curve is named for the direction it bows out, or deviates, toward. This side of outward bowing is the convex side, which is the side experiencing the most tension and stretching of the surrounding tissues. This established rule ensures a clear and unambiguous way to classify the overall direction of the spinal deviation. While the concave side is also important, the convex side determines the curve’s technical name.
How Scoliosis Curves Are Documented
The classification and documentation of scoliosis curves rely on identifying anatomical points, which are most easily seen on an X-ray taken from the back (posterior-anterior view). A diagnosis of scoliosis requires a lateral spinal curve that measures at least 10 degrees. This measurement of magnitude is known as the Cobb angle, which quantifies the severity of the curve.
The Cobb angle is determined by drawing lines along the top of the most-tilted vertebra above the curve and the bottom of the most-tilted vertebra below the curve. The intersection of perpendicular lines drawn from these two endplates yields the angle measurement. The full classification also includes the curve’s apex, which is the single most rotated and laterally deviated vertebra, always found on the convex side. The location of this apex, such as the thoracic or lumbar spine, is used alongside the direction of convexity to fully describe the curve.
Applying Directional Terminology
The rule of naming the curve by its convexity translates directly into the specific clinical terminology used by healthcare providers. There are two primary directional terms used in scoliosis nomenclature, both derived from Latin roots. A curve that bows out to the right is known as Dextroscoliosis (“dextro” meaning right). In contrast, a curve that bows out to the left is called Levoscoliosis (“levo” meaning left).
This directional name is often combined with the location of the apex to create a complete diagnosis, such as “Thoracic Dextroscoliosis” or “Lumbar Levoscoliosis”. Although the concave side is subject to compression and shortening of the muscles and ligaments, the convex side provides the outward directional marker that is globally recognized for classification.