title: Validation and reliability analysis of the new SRS-Schwab classification for adult spinal deformity.
abstract: METHODS
  An inter- and intra-observer reliability study.
  
  
  OBJECTIVE
  To determine the inter- and intra-observer reliabilities of the new SRS-Schwab system for classifying adult spinal deformity (ASD) using nonpremarked cases.
  
  
  BACKGROUND
  Schwab et al reported excellent inter- and intra-observer reliability and interobserver agreement for classification based on curve type and 3 modifiers.
  
  
  METHODS
  A total of 102 patients with ASD were included in this study, which was conducted from February 2009 to January 2012. Long-cassette standing posterior-anterior and lateral radiographs of the spine and the pelvis were obtained from patients with ASD in the fist-on-clavicle position. All 102 cases were classified according to the new SRS-Schwab classification by 4 observers. After a 2-week interval, the same classification was independently repeated by each observer with the cases in a different randomly assigned order. The Fless κ coefficient was calculated to test the inter- and intra-observer reliabilities of the new SRS-Schwab classification.
  
  
  RESULTS
  With the new SRS-Schwab classification system, 12 patients were classified as having a type T curve, 30 cases as having a type L, 45 cases as having a type D, and 15 cases as having a type S. For overall classification, the mean κ value was 0.73 for interobserver reliability and 0.83 for intraobserver reliability. Disagreements occurred most often when differentiating type T curves from type L curves and when determining the pelvic incidence minus lumbar lordosis modifier.
  
  
  CONCLUSIONS
  With the nonpremarked cases, this new SRS-Schwab system for patients with ASD could achieve good to excellent intra- and inter-observer reliability, but the definition of thoracic or lumbar curves was still predisposed to confusion. Overall, the SRS-Schwab system is a simple and clear classification system with incorporated spinopelvic parameters, which significantly increase its value for practical usage.
authors.affiliation: School of Medicine, Southeast University, Nanjing, Jiangsu Province, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: Zhen
authors.initials: Z
authors.lastname: Liu
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
authors.forename: Bang-ping
authors.initials: BP
authors.lastname: Qian
authors.forename: Zezhang
authors.initials: Z
authors.lastname: Zhu
authors.forename: Leilei
authors.initials: L
authors.lastname: Xu
authors.forename: Yitao
authors.initials: Y
authors.lastname: Ding
authors.forename: Yong
authors.initials: Y
authors.lastname: Qiu
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D010388:Pelvis / Q000000981:diagnostic imaging; D011859:Radiography / Q000379:methods*; D015203:Reproducibility of Results; D012600:Scoliosis / Q000145:classification* / Q000175:diagnosis / Q000000981:diagnostic imaging*; D013131:Spine / Q000000981:diagnostic imaging*