Inter- and Intra-rater Agreement in Assessment of Adult Spinal Deformity Using the Scoliosis Research Society–Schwab Classification

Study DesignCross-sectional assessment of inter- and intra-rater agreement.ObjectivesTo assess inter- and intra-rater agreement between spine surgeons with different levels of experience in a large consecutive series of adult patients referred to a tertiary institution for evaluation of a spinal deformity using the Scoliosis Research Society (SRS)–Schwab classification.BackgroundThe development of the SRS-Schwab classification of adult spinal deformity is based on current knowledge about relevant radiographic variables related to health-related quality of life. Clinical implementation of the classification requires satisfactory reliability. Two recent reports on agreement were based on a small selected case sample using pre-marked radiographs and a large cohort of only surgical patients, including congenital deformity.MethodsScoliosis Research Society–Schwab classification of 67 consecutive adult patients referred for surgical evaluation of a spinal deformity was done in a blinded fashion without pre-marking by 2 senior spine surgeons, 1 attending, and 1 spine fellow. After 2 weeks, the classification was repeated on recoded radiographs. Inter- and intra-rater agreement was analyzed using Fleiss kappa statistics. Rater bias was assessed using Bhapkar test for marginal homogeneity.ResultsAccording to Landis and Koch, the observed agreements were considered substantial to almost perfect for curve type and sagittal modifiers and moderate for entire grade, with no consistent differences between surgeons with different levels of experience.ConclusionsThe results for each individual radiographic parameter correspond to previous findings and support use of the SRS-Schwab classification in adult spinal deformity. The results for entire grade were considered only moderate. The authors recommend that it is not used as an individual parameter.