title: Radiographic evaluation of osteoarthritis of the hip: an inter-observer study of 61 hips treated for late-detected developmental hip dislocation.
abstract: OBJECTIVE
  Different methods have been used to classify osteoarthritis (OA) of the hip. We evaluated the reliability of different classifications in order to find which grading system is most appropriate for use in clinical practice.
  
  
  METHODS
  49 patients (61 affected hips) with late-detected developmental dislocation of the hip (DDH) were studied. The mean age at follow-up was 45 (32-49) years. 3 classifications of OA were compared. The gradings by Kellgren and Lawrence (1957) (K&L) and Croft et al. (1990) are global visual assessments based on osteophytes, cysts, subchondral sclerosis, and narrowing of the joint space. The third classification is based on narrowing in the upper, weight-bearing part of the joint and defines as OA a minimum joint space width (JSW) of less than 2.0 mm at the narrowest part. 2 experienced observers, one radiologist and one orthopedic surgeon, assessed and measured the radiographs.
  
  
  RESULTS
  Minimum JSW (< 2.0 mm in 9 hips) gave the best inter-observer agreement (kappa value = 0.87). Using the K&L grading, inter-observer agreement was moderate (kappa = 0.55), but kappa increased when the number of categories was reduced from 5 to 3 (no OA, mild OA, and severe OA). The Croft classification gave similar agreement as the K&L grading. The intra-observer agreement was better than inter-observer agreement, irrespective of the grading system. There was a good accordance between the minimum JSW and the 2 other methods.
  
  
  CONCLUSIONS
  Joint space narrowing using a minimum JSW of < 2.0 mm as criterion for OA was the simplest and most reproducible classification in long-term follow-up of patients with DDH. A classification based on global visual assessment can be used in addition if only hips with severe OA are included.
authors.affiliation: Department of Orthopaedics, Oslo University Hospital, Norway. terje.terjesen@rikshospitalet.no
authors.forename: Terje
authors.initials: T
authors.lastname: Terjesen
authors.forename: Ragnhild B
authors.initials: RB
authors.lastname: Gunderson
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D005500:Follow-Up Studies; D006618:Hip Dislocation, Congenital / Q000150:complications* / Q000000981:diagnostic imaging* / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015207:Osteoarthritis, Hip / Q000145:classification* / Q000000981:diagnostic imaging / Q000453:epidemiology*; D015995:Prevalence; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies