The SRS classification for adult spinal deformity: building on the King/Moe and Lenke classification systems.

STUDY DESIGN Descriptive study of the Scoliosis Research Society (SRS) Classification for Adult Spinal Deformity using interobserver reliability measures for validation of the system. OBJECTIVES To propose and validate a classification system for adult spinal deformity that will have utility in reporting on treatment options and outcomes for affected adults. SUMMARY OF BACKGROUND DATA Classification systems exist for adolescent idiopathic scoliosis and have utility in categorizing spinal deformity and guiding choices for management. Adult spinal deformity is distinct from adolescent deformity. Important distinctions include present impairment and pain, regional and global decompensation, and degenerative changes within the deformity. A useful classification system for adult spinal deformity does not exist. The absence of a classification system for adult deformity compromises the ability to report on similar cases and to develop an evidence-based approach to care. METHODS Descriptive study design with development of an SRS Classification System using the Delphi Method. Validation of the system using interobserver reliability measures based on responses of SRS-member surgeons to radiographic case presentations. RESULTS Nineteen surgeons evaluated 25 cases of adult spinal deformity. Interobserver reliability for curve types (kappa = 0.64), regional sagittal modifiers (kappa = 0.73), and degenerative lumbar modifiers (kappa = 0.65) were substantial. Interobserver reliability was moderate (kappa = 0.56) for choosing a cephalad level for operative treatment and substantial for choosing a caudad level (kappa = 0.77). CONCLUSIONS A uniform system for classification of adult spinal deformity has significant utility in improving the ability of surgeons and authors to compare and combine similar cases, and in improving the accuracy of reports on the outcomes of care for adults with spinal deformity. The SRS Classification System for Adult Spinal Deformity has good interobserver reliability and is predictive of surgical strategies. Further validation of the SRS Classification System will include measures of intraobserver reliability, and inclusion of clinical characteristics of patient presentation and comorbidities.