title: Reliability and stability of three common classifications for Legg-Calvé-Perthes disease.
abstract: BACKGROUND
  To predict the course of Legg-Calvé-Perthes disease (LCPD) and select between treatment options in the early stages, it is critical to have a reliable predictive classification.
  
  
  OBJECTIVE
  We examined the reliability and stability of three common classification systems for LCPD.
  
  
  METHODS
  We identified 69 patients with LCPD, who had hip radiographs taken more than twice after the initial presentation with at least a 3-month interval. The Herring lateral pillar, Catterall, and Salter-Thompson classifications were evaluated in terms of reliability and stability. The inter- and intrarater reliability of the classification systems was determined by three orthopaedic surgeons using intraclass correlation coefficients (ICCs). To evaluate the stability of the classification systems, the percentage agreement and ICCs among the initial rating, rating when entering fragmentation, and final rating were used.
  
  
  RESULTS
  The interrater reliability was highest in Herring lateral pillar classification (ICC, 0.885) followed by the Catterall and Salter-Thompson classifications (ICC, 0.802 and 0.702, respectively). The percentage agreement and ICC between the initial and final rating were, respectively, 55% and 0.491 for the Herring classification and 48% and 0.378 for the Catterall classification.
  
  
  CONCLUSIONS
  Our data show the highest reliability of the classification of Herring et al. However, more than 40% of the hip radiographs at the initial presentation, and in particular, most of Herring Group A patients, were upgraded. Therefore, for patients older than 8 years old and graded as Herring Group A initially, surgeons should keep the possibility of surgical treatment in mind.
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, 300 Gumi-Dong, Bundang-Gu, Sungnam, Kyungki 463-707, Korea.
authors.forename: Moon Seok
authors.initials: MS
authors.lastname: Park
authors.forename: Chin Youb
authors.initials: CY
authors.lastname: Chung
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Tae Won
authors.initials: TW
authors.lastname: Kim
authors.forename: Ki Hyuk
authors.initials: KH
authors.lastname: Sung
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007873:Legg-Calve-Perthes Disease / Q000145:classification / Q000000981:diagnostic imaging* / Q000628:therapy; D008297:Male; D015588:Observer Variation; D011237:Predictive Value of Tests; D011379:Prognosis; D011859:Radiography; D015203:Reproducibility of Results; D056910:Republic of Korea; D012189:Retrospective Studies; D013997:Time Factors