title: Systematic analysis of classification systems for osteonecrosis of the femoral head.
abstract: BACKGROUND
  Multiple classification systems for osteonecrosis of the hip have been developed to assist physicians in the diagnosis and treatment of this potentially debilitating disorder. The purpose of this analysis was to delineate the classification systems utilized in reports published since 1985 and, through a comparison of the most commonly used systems, to identify consistent factors that would allow for cross-publication comparisons to be made.
  
  
  METHODS
  We performed a PubMed search for reports of outcome studies concerning treatment methods for osteonecrosis of the hip. All studies of reported outcomes with greater than ten patients were included in the analysis. Various classification systems were tabulated to determine usage frequencies. The four most commonly used systems were then analyzed to determine common factors used for classification.
  
  
  RESULTS
  One hundred and fifty-seven studies were available for analysis. Sixteen major classification systems that made use of more than one radiographic factor were identified, and nine of these systems had one to five modifications reported throughout the literature. Additionally, eleven other systems made use of single factors obtained from either magnetic resonance imaging or anatomic data. The review revealed that four classification systems accounted for greater than 85.4% of the reported studies. Parameters for these four systems were stratified to allow for uniformity of patient or study evaluation.
  
  
  CONCLUSIONS
  This analysis of the reported classification systems for osteonecrosis of the femoral head revealed several similarities between the most commonly used systems. An analysis of patients can be made with any of the four major systems if specific data are collected according to various magnetic resonance imaging and radiographic findings. This approach will allow for easier comparison of studies across different centers.
  
  
  METHODS
  Prognostic Level III. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.
authors.affiliation: Rubin Institute for Advanced Orthopedics, Center for Joint Preservation and Reconstruction, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Baltimore, MD 21215, USA. Rhondamont@aol.com
authors.forename: Michael A
authors.initials: MA
authors.lastname: Mont
authors.forename: German A
authors.initials: GA
authors.lastname: Marulanda
authors.forename: Lynne C
authors.initials: LC
authors.lastname: Jones
authors.forename: Khaled J
authors.initials: KJ
authors.lastname: Saleh
authors.forename: Noah
authors.initials: N
authors.lastname: Gordon
authors.forename: David S
authors.initials: DS
authors.lastname: Hungerford
authors.forename: Marvin E
authors.initials: ME
authors.lastname: Steinberg
mesh_terms: D002965:Classification / Q000379:methods; D005271:Femur Head Necrosis / Q000145:classification* / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D011859:Radiography; D012720:Severity of Illness Index