title: Predictive factors for the progression of spontaneous osteonecrosis of the knee.
abstract: OBJECTIVE
  To assess potentially predictive factors that were evaluated 1 year after the onset of symptoms in patients with spontaneous osteonecrosis of the knee (SONK) and to determine receiver operating characteristic (ROC) curve cut-off values.
  
  
  METHODS
  Within 1 year of symptom onset, patients with SONK-selected treatment options, mainly based on severity of pain, chose either conservative treatment (n = 27 knees) or operative treatment (n = 27 knees). Knee and whole-leg radiographs, knee MRIs and bone mineral density scans of the lumbar spine, femoral neck and femoral condyles were obtained. The parameters measured were: (1) anatomical angle on whole-leg radiograph and (2) lesion size and medial meniscus extrusion on MRI.
  
  
  RESULTS
  The anatomical angle and lesion size in the sagittal section (depth) on MRI were markedly larger in the operative treatment group than those in the conservative treatment group. The anatomical angle and depth on MRI of SONK at Stages 1-3 were significantly different between groups, with odds ratios (95 % confidence intervals) of 1.16 (1.18-2.34) and 1.11 (1.01-1.23). One year after symptom onset, ROC curve cut-off value for anatomical angle was 180° and depth on MRI was 20 mm.
  
  
  CONCLUSIONS
  An anatomical angle >180° and depth >20 mm on MRI were predictive factors for a poorer prognosis 1 year after symptom onset in patients with SONK. Our results on radiographs and MRI provided a predictive prognosis for patients with SONK at the initial visit to their orthopaedic surgeons.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan. akamatsu@yokohama-cu.ac.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Akamatsu
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kusayama
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Aratake
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kumagai
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Saito
mesh_terms: D000328:Adult; D000368:Aged; D018450:Disease Progression; D005260:Female; D005269:Femur / Q000503:physiopathology; D005272:Femur Neck; D005544:Forecasting; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology; D008875:Middle Aged; D010020:Osteonecrosis / Q000473:pathology*; D011379:Prognosis; D012372:ROC Curve; D011859:Radiography
keywords: Anatomical angle; Knee; Lesion size; MRI; Spontaneous osteonecrosis