Curve Prevalence of a New Classification of Operative Adolescent Idiopathic Scoliosis

STUDY DESIGN: A retrospective multicenter consecutive case review of operative adolescent idiopathic scoliosis. OBJECTIVES: To define the curve prevalence of a large consecutive series of cases with operative adolescent idiopathic scoliosis as classified by a new system and to test the ability of this new classification system to correlate with regions of the scoliotic spine to be instrumented/fused. SUMMARY OF BACKGROUND DATA: A new comprehensive, two-dimensional classification system, intended to be treatment based, has been developed. However, it has not been tested whether all presenting operative cases of adolescent idiopathic scoliosis are classifiable in a large consecutive series, nor has the prevalence of specific curve types been determined. In addition, it is unknown whether this classification is truly treatment based, as to whether it can correlate with regions of the spine to be instrumented/fused. METHODS: A multicenter retrospective review of 606 consecutive operative cases of adolescent idiopathic scoliosis was performed. All cases were classified by a new triad classification system, which included the following: a curve type (1-6), a lumbar spine modifier (A, B, C), and a sagittal thoracic modifier (-, N, +). Prevalence of the individual three components of the system and the classification grouping of all three components together were performed. In addition, the authors assessed whether this system could correlate with regions of the spine that should be included in the instrumentation and fusion, based on exactly which regions were fused during the operative procedure. RESULTS: All 606 cases were classifiable by this system. Prevalence of the six curve types noted was as follows: Type 1, main thoracic (n = 305, 51%); Type 2, double thoracic (n = 118, 20%); Type 3, double major (n = 69, 11%); Type 4, triple major (n = 19, 3%); Type 5, thoracolumbar/lumbar (n = 74, 12%); and Type 6, thoracolumbar/lumbar-main thoracic (n = 17, 3%). The five most common curve classifications noted were as follows: 1AN, 1BN, 2AN, 5CN, and 1CN, which accounted for 58% of all curve classifications noted. An average of 90% of the operative cases had surgically structural regions of the spine included in the instrumentation and fusion as predicted by the curve type. CONCLUSIONS: A new comprehensive classification system for operative adolescent idiopathic scoliosis found all 606 consecutive cases of adolescent idiopathic scoliosis classifiable, with the Type 1, main thoracic curve pattern, the most common curve type found (51%). This new classification system appears to correlate with treatment of surgically structural regions of the spine fused in 90% of cases by the objective radiographic criteria used.