title: Reliability of the Spinal Deformity Study Group classification of lumbosacral spondylolisthesis.
abstract: METHODS
  Reliability study of the computer-assisted SDSG (Spinal Deformity Study Group) classification of lumbosacral spondylolisthesis.
  
  
  OBJECTIVE
  To assess the intra- and interobserver reliability of the computer-assisted SDSG classification of lumbosacral spondylolisthesis.
  
  
  BACKGROUND
  The SDSG has proposed a new classification of lumbosacral spondylolisthesis based on slip grade, pelvic incidence (PI), and sacro-pelvic and spinal balance. Three types of low-grade spondylolisthesis are described: low PI (type 1), normal PI (type 2), and high PI (type 3). High-grade spondylolisthesis are defined as type 4 (balanced sacro-pelvis), type 5 (retroverted sacro-pelvis with balanced spine), and type 6 (retroverted sacro-pelvis with unbalanced spine).
  
  
  METHODS
  Full-length standing lateral radiographs of the spine of 40 subjects with lumbosacral spondylolisthesis were reviewed twice by 7 observers. Custom software was used by the observers to identify 7 anatomical landmarks on each radiograph to determine the SDSG type for all subjects. Percentage of agreement and κ coefficients were used to determine the intra- and interobserver reliability.
  
  
  RESULTS
  All 6 types of spondylolisthesis described in the computer-assisted SDSG classification were identified. Overall intra- and interobserver agreements were 80% (κ: 0.74) and 71% (κ: 0.65), respectively. The intra- and interobserver agreements associated with computerized determination of slip grade were 92% (κ: 0.83) and 88% (κ: 0.78), respectively. As for computerized determination of sacro-pelvic and spinal balance, intra- and interobserver agreements were 86% (κ: 0.76) and 75% (κ: 0.63) for low-grade slips, whereas they were 88% (κ: 0.80) and 83% (κ: 0.75) for high-grade slips.
  
  
  CONCLUSIONS
  Substantial intra- and interobserver reliability was found for the computer-assisted SDSG classification, and all 6 types of lumbosacral spondylolisthesis were identified. Refinement of the computer-assisted classification technique is, however, needed to further increase the reliability of the SDSG classification and facilitate its clinical use.
authors.affiliation: Department of Surgery, University of Montreal, Montreal, Canada. macthiong@gmail.com
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Mac-Thiong
authors.forename: Luc
authors.initials: L
authors.lastname: Duong
authors.forename: Stefan
authors.initials: S
authors.lastname: Parent
authors.forename: Michael Timothy
authors.initials: MT
authors.lastname: Hresko
authors.forename: John R
authors.initials: JR
authors.lastname: Dimar
authors.forename: Mark
authors.initials: M
authors.lastname: Weidenbaum
authors.forename: Hubert
authors.initials: H
authors.lastname: Labelle
mesh_terms: D000293:Adolescent; D000886:Anthropometry / Q000379:methods*; D002648:Child; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D011859:Radiography / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging* / Q000473:pathology; D013168:Spondylolisthesis / Q000145:classification* / Q000000981:diagnostic imaging* / Q000473:pathology; D055815:Young Adult