Classification of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis is the most common type of scoliosis. Several classification systems have been developed in order to identify the different subtypes; to support communication; to provide treatment guidelines; and to prognosticate the outcome. In 1905, Schulthess described the first classification system for scoliotic curves, based on curve location. In 1983, King et al. described the first classification system for scoliosis based on treatment guidelines. They identified five thoracic curve patterns and recommended different fusion levels for different curve patterns when Harrington instrumentation was used. However, when more modern instrumentation systems are used, King classification fails to give accurate guidelines in determining the proper levels for fusion, being also not comprehensive enough to categorize all scoliosis patterns. In 2001, Lenke proposed a new classification system for scoliotic curve based on curve location, magnitude, and flexibility, as well as on a lumbar and a sagittal modifier. Lenke classification represents a useful tool for determining the extent of spinal fusion and shows a higher intra- and interobserver reliability. However, it does not take into account the rotational dimension of the deformity. Recently, three dimensional classification systems for AIS have been proposed, but their real clinical application is far from being defined.