title: The classification of osteonecrosis in patients with cancer: validation of a new radiological classification system.
abstract: OBJECTIVE
  To validate a new, non-joint-specific radiological classification system that is suitable regardless of the site of the osteonecrosis (ON) in patients with cancer.
  
  
  METHODS
  Critical deficiencies in the existing ON classification systems were identified and a new, non-joint-specific radiological classification system was developed. Seventy-two magnetic resonance imaging (MRI) images of patients with cancer and ON lesions were graded, and the validation of the new system was performed by assessing inter- and intra-observer reliability.
  
  
  RESULTS
  Intra-observer reliability of ON grading was good or very good, with kappa values of 0.79-0.86. Interobserver agreement was lower but still good, with kappa values of 0.62-0.77. Ninety-eight percent of all intra- or interobserver differences were within one grade. Interobserver reliability of assessing the location of ON was very good, with kappa values of 0.93-0.98.
  
  
  CONCLUSIONS
  All the available radiological ON classification systems are joint specific. This limitation has spurred the development of multiple systems, which has led to the insufficient use of classifications in ON studies among patients with cancer. The introduced radiological classification system overcomes the problem of joint-specificity, was found to be reliable, and can be used to classify all ON lesions regardless of the affected site.
authors.affiliation: Department of Surgery, Oulu University Hospital and Oulu University, Oulu, Finland. Electronic address: tuukka.niinimaki@fimnet.fi.
authors.forename: T
authors.initials: T
authors.lastname: Niinimäki
authors.affiliation: Department of Radiology, Oulu University Hospital, Oulu, Finland; Oulu University, Oulu, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Niinimäki
authors.affiliation: Department of Radiology, Oulu University Hospital, Oulu, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Halonen
authors.affiliation: Department of Surgery, Oulu University Hospital and Oulu University, Oulu, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Hänninen
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Harila-Saari
authors.affiliation: Department of Children and Adolescents, Oulu University Hospital and Oulu University, Oulu, Finland.
authors.forename: R
authors.initials: R
authors.lastname: Niinimäki
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D015588:Observer Variation; D010020:Osteonecrosis / Q000145:classification* / Q000150:complications* / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult