title: Development and initial validation of the Classification of Early-Onset Scoliosis (C-EOS).
abstract: BACKGROUND
  Early-onset scoliosis is a heterogeneous condition, with highly variable manifestations and natural history. No standardized classification system exists to describe and group patients, to guide optimal care, or to prognosticate outcomes within this population. A classification system for early-onset scoliosis is thus a necessary prerequisite to the timely evolution of care of these patients.
  
  
  METHODS
  Fifteen experienced surgeons participated in a nominal group technique designed to achieve a consensus-based classification system for early-onset scoliosis. A comprehensive list of factors important in managing early-onset scoliosis was generated using a standardized literature review, semi-structured interviews, and open forum discussion. Three group meetings and two rounds of surveying guided the selection of classification components, subgroupings, and cut-points. Initial validation of the system was conducted using an interobserver reliability assessment based on the classification of a series of thirty cases.
  
  
  RESULTS
  Nominal group technique was used to identify three core variables (major curve angle, etiology, and kyphosis) with high group content validity scores. Age and curve progression ranked slightly lower. Participants evaluated the cases of thirty patients with early-onset scoliosis for reliability testing. The mean kappa value for etiology (0.64) was substantial, while the mean kappa values for major curve angle (0.95) and kyphosis (0.93) indicated almost perfect agreement. The final classification consisted of a continuous age prefix, etiology (congenital or structural, neuromuscular, syndromic, and idiopathic), major curve angle (1, 2, 3, or 4), and kyphosis (-, N, or +) variables, and an optional progression modifier (P0, P1, or P2).
  
  
  CONCLUSIONS
  Utilizing formal consensus-building methods in a large group of surgeons experienced in treating early-onset scoliosis, a novel classification system for early-onset scoliosis was developed with all core components demonstrating substantial to excellent interobserver reliability. This classification system will serve as a foundation to guide ongoing research efforts and standardize communication in the clinical setting.
authors.affiliation: Department of Orthopaedic Surgery (B.A.W., D.J.M., D.P.R., and M.G.V.), and Division of Pediatric Orthopaedic Surgery (H.M.), Columbia University Medical Center, 3959 Broadway, 8 North, New York, NY 10032. E-mail address for M.G. Vitale: mgv1@columbia.edu.
authors.forename: Brendan A
authors.initials: BA
authors.lastname: Williams
authors.affiliation: Department of Orthopaedic Surgery (B.A.W., D.J.M., D.P.R., and M.G.V.), and Division of Pediatric Orthopaedic Surgery (H.M.), Columbia University Medical Center, 3959 Broadway, 8 North, New York, NY 10032. E-mail address for M.G. Vitale: mgv1@columbia.edu.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopaedic Surgery (B.A.W., D.J.M., D.P.R., and M.G.V.), and Division of Pediatric Orthopaedic Surgery (H.M.), Columbia University Medical Center, 3959 Broadway, 8 North, New York, NY 10032. E-mail address for M.G. Vitale: mgv1@columbia.edu.
authors.forename: Daren J
authors.initials: DJ
authors.lastname: McCalla
authors.affiliation: San Diego Center for Spinal Disorders, 4130 La Jolla Village Drive, Suite 300, San Diego, La Jolla, CA 92037.
authors.forename: Behrooz A
authors.initials: BA
authors.lastname: Akbarnia
authors.affiliation: Department of Orthopaedic Surgery and Sports Medicine, Children's National Medical Center, 111 Michigan Avenue, N.W., Washington, DC 20010.
authors.forename: Laurel C
authors.initials: LC
authors.lastname: Blakemore
authors.affiliation: Department of Orthopaedic Surgery, Shriner's Hospital for Children, 3551 North Broad Street, Philadelphia, PA 19140.
authors.forename: Randal R
authors.initials: RR
authors.lastname: Betz
authors.affiliation: Division of Orthopaedics, Children's Hospital of Philadelphia, 324 South 34th Street, Philadelphia, PA 19104.
authors.forename: John M
authors.initials: JM
authors.lastname: Flynn
authors.affiliation: Department of Orthopedic Surgery, Texas Scottish Rite Hospital for Children, 2222 Welborn Street, Dallas, TX 75219.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Johnston
authors.affiliation: Departments of Orthopaedics and Pediatrics, University of Arkansas for Medical Sciences, 1 Children's Way, Little Rock, AR 72202.
authors.forename: Richard E
authors.initials: RE
authors.lastname: McCarthy
authors.affiliation: Department of Orthopaedic Surgery (B.A.W., D.J.M., D.P.R., and M.G.V.), and Division of Pediatric Orthopaedic Surgery (H.M.), Columbia University Medical Center, 3959 Broadway, 8 North, New York, NY 10032. E-mail address for M.G. Vitale: mgv1@columbia.edu.
authors.forename: David P
authors.initials: DP
authors.lastname: Roye
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 Sunset Boulevard, Mailstop #69, Los Angeles, CA 90027.
authors.forename: David L
authors.initials: DL
authors.lastname: Skaggs
authors.affiliation: Department of Orthopaedics and Pediatrics, The University of Utah School of Medicine, Primary Children's Medical Center, 100 Mario Capecchi Drive, Salt Lake City, UT 84113.
authors.forename: John T
authors.initials: JT
authors.lastname: Smith
authors.affiliation: Department of Orthopaedic Surgery, Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Snyder
authors.affiliation: Department of Orthopaedic Surgery, The Johns Hopkins University, 1800 Orleans Street, 7359A, Baltimore, MD 21287.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Sponseller
authors.affiliation: Division of Orthopaedic Surgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45267.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Sturm
authors.affiliation: Division of Pediatric Orthopaedic Surgery, Rainbow Babies and Children's Hospital, University Hospitals Case Medical Center, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106.
authors.forename: George H
authors.initials: GH
authors.lastname: Thompson
authors.affiliation: Department of Orthopaedics and Traumatology, Hacettepe University, 06100 Sihhiye, Ankara, Turkey.
authors.forename: Muharrem
authors.initials: M
authors.lastname: Yazici
authors.affiliation: Department of Orthopaedic Surgery (B.A.W., D.J.M., D.P.R., and M.G.V.), and Division of Pediatric Orthopaedic Surgery (H.M.), Columbia University Medical Center, 3959 Broadway, 8 North, New York, NY 10032. E-mail address for M.G. Vitale: mgv1@columbia.edu.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Vitale
mesh_terms: D017668:Age of Onset; D006801:Humans; D015588:Observer Variation; D012600:Scoliosis / Q000145:classification* / Q000209:etiology / Q000473:pathology