title: AO spine injury classification system: a revision proposal for the thoracic and lumbar spine.
abstract: OBJECTIVE
  The AO Spine Classification Group was established to propose a revised AO spine injury classification system. This paper provides details on the rationale, methodology, and results of the initial stage of the revision process for injuries of the thoracic and lumbar (TL) spine.
  
  
  METHODS
  In a structured, iterative process involving five experienced spine trauma surgeons from various parts of the world, consecutive cases with TL injuries were classified independently by members of the classification group, and analyzed for classification reliability using the Kappa coefficient (κ) and for accuracy using latent class analysis. The reasons for disagreements were examined systematically during review meetings. In four successive sessions, the system was revised until consensus and sufficient reproducibility were achieved.
  
  
  RESULTS
  The TL spine injury system is based on three main injury categories adapted from the original Magerl AO concept: A (compression), B (tension band), and C (displacement) type injuries. Type-A injuries include four subtypes (wedge-impaction/split-pincer/incomplete burst/complete burst); B-type injuries are divided between purely osseous and osseo-ligamentous disruptions; and C-type injuries are further categorized into three subtypes (hyperextension/translation/separation). There is no subgroup division. The reliability of injury types (A, B, C) was good (κ = 0.77). The surgeons' pairwise Kappa ranged from 0.69 to 0.90. Kappa coefficients κ for reliability of injury subtypes ranged from 0.26 to 0.78.
  
  
  CONCLUSIONS
  The proposed TL spine injury system is based on clinically relevant parameters. Final evaluation data showed reasonable reliability and accuracy. Further validation of the proposed revised AO Classification requires follow-up evaluation sessions and documentation by more surgeons from different countries and backgrounds and is subject to modification based on clinical parameters during subsequent phases.
authors.affiliation: Department of Orthopaedic Surgery, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Reinhold
authors.forename: Laurent
authors.initials: L
authors.lastname: Audigé
authors.forename: Klaus John
authors.initials: KJ
authors.lastname: Schnake
authors.forename: Carlo
authors.initials: C
authors.lastname: Bellabarba
authors.forename: Li-Yang
authors.initials: LY
authors.lastname: Dai
authors.forename: F Cumhur
authors.initials: FC
authors.lastname: Oner
mesh_terms: D032921:Consensus; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000145:classification* / Q000175:diagnosis; D008159:Lumbar Vertebrae / Q000293:injuries*; D017410:Practice Guidelines as Topic; D015203:Reproducibility of Results; D016103:Spinal Fractures / Q000145:classification* / Q000175:diagnosis; D013904:Thoracic Vertebrae / Q000293:injuries*; D015599:Trauma Severity Indices