Adolescent idiopathic scoliosis

Background: The lack of a reliable, universally acceptable system for class ification of adolescent idiopathic scoliosis has made comparisons between v arious types of operative treatment an impossible task. Furthermore, long-t erm outcomes cannot be determined because of the great variations in the de scription of study groups. Methods: We developed a new classification system with three components: cu rve type (1 through 6), a lumbar spine modifier (A, B, or C), and a sagitta l thoracic modifier (-, N, or +). The six curve types have specific charact eristics, on coronal and sagittal radiographs, that differentiate structura l and nonstructural curves in the proximal thoracic, main thoracic, and tho racolumbar/lumbar regions. The lumbar spine modifier is based on the relati onship of the center sacral vertical line to the apex of the lumbar curve, and the sagittal thoracic modifier is based on the sagittal curve measureme nt from the fifth to the twelfth thoracic level. A minus sign represents a curve of less than +10 degrees, N represents a curve of 10 degrees to 40 de grees, and a plus sign represents a curve of more than +40 degrees. Five su rgeons, members of the Scoliosis Research Society who had developed the new system and who had previously tested the reliability of the King classific ation on radiographs of twenty-seven patients, measured the same radiograph s (standing coronal and lateral as well as supine side-bending views) to te st the reliability of the new classification. A randomly chosen independent group of seven surgeons, also members of the Scoliosis Research Society, t ested the reliability and validity of the classification as well. Results: The interobserver and intraobserver kappa values for the curve typ e were, respectively, 0.92 and 0.83 for the five developers of the system a nd 0.740 and 0.893 for the independent group of seven scoliosis surgeons. I n the independent group, the mean interobserver and intraobserver kappa val ues were 0.800 and 0.840 for the lumbar modifier and 0.938 and 0.970 for th e sagittal thoracic modifier. These kappa values were all in the good-to-ex cellent range (>0.75), except for the interobserver reliability of the inde pendent group for the curve type (kappa = 0.74), which fell just below this level. Conclusions: This new two-dimensional classification of adolescent idiopath ic scoliosis, as tested by two groups of surgeons, was shown to be much mor e reliable than the King system. Additional studies are necessary to determ ine the versatility, reliability, and accuracy of the classification for de fining the vertebrae to be included in an arthrodesis.