title: The comprehensive anatomical spinal osteotomy classification.
abstract: BACKGROUND
  Global sagittal malalignment is significantly correlated with health-related quality-of-life scores in the setting of spinal deformity. In order to address rigid deformity patterns, the use of spinal osteotomies has seen a substantial increase. Unfortunately, variations of established techniques and hybrid combinations of osteotomies have made comparisons of outcomes difficult.
  
  
  OBJECTIVE
  To propose a classification system of anatomically-based spinal osteotomies and provide a common language among spine specialists.
  
  
  METHODS
  The proposed classification system is based on 6 anatomic grades of resection (1 through 6) corresponding to the extent of bone resection and increasing degree of destabilizing potential. In addition, a surgical approach modifier is added (posterior approach or combined anterior and posterior approaches). Reliability of the classification system was evaluated by an analysis of 16 clinical cases, rated 2 times by 8 different readers, and calculation of Fleiss kappa coefficients.
  
  
  RESULTS
  Intraobserver reliability was classified as 'almost perfect'; Fleiss kappa coefficient averaged 0.96 (range, 0.92-1.0) for resection type and 0.90 (0.71-1.0) for the approach modifier. Results from the interobserver reliability for the classification were 0.96 for resection type and 0.88 for the approach modifier.
  
  
  CONCLUSIONS
  This proposed anatomically based classification system provides a consistent description of the various osteotomies performed in spinal deformity correction surgery. The reliability study confirmed that the classification is simple and consistent. Further development of its use will provide a common frame for osteotomy assessment and permit comparative analysis of different treatments.
authors.affiliation: *NYU Hospital for Joint Diseases, New York, New York; ‡Orthopedic Department Aix-Marseille University, Marseille, France; §Washington University School of Medi cine, St. Louis, Missouri; ‖Neurosurgery, University of California San Francisco, San Francisco, California; ¶Neurological Surgery, University of Virginia, Charlottesville, Virginia; #Spine Institute for Special Surgery, University of Louisville, Kentucky; **Maimonides Medical Center, New York, New York.
authors.forename: Frank
authors.initials: F
authors.lastname: Schwab
authors.forename: Benjamin
authors.initials: B
authors.lastname: Blondel
authors.forename: Edward
authors.initials: E
authors.lastname: Chay
authors.forename: Jason
authors.initials: J
authors.lastname: Demakakos
authors.forename: Lawrence
authors.initials: L
authors.lastname: Lenke
authors.forename: Patrick
authors.initials: P
authors.lastname: Tropiano
authors.forename: Christopher
authors.initials: C
authors.lastname: Ames
authors.forename: Justin S
authors.initials: JS
authors.lastname: Smith
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.forename: Steven
authors.initials: S
authors.lastname: Glassman
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Farcy
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
mesh_terms: D006801:Humans; D015588:Observer Variation; D010027:Osteotomy / Q000145:classification* / Q000379:methods; D011859:Radiography; D015203:Reproducibility of Results; D013131:Spine / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D009626:Terminology as Topic; D021801:Zygapophyseal Joint / Q000601:surgery