title: [Influencing factors of disease progression for asymptomatic osteonecrosis of the femoral head].
abstract: OBJECTIVE
  To analyze the progression of asymptomatic osteonecrosis of the femoral head by evaluating its lesion size and location.
  
  
  METHODS
  From January 2008 to June 2009, 24 cases or hips were available for outcome analysis. There were 16 males and 8 females with a mean age of 36.4 (22-46) years and a mean body mass index of 25.4 (17.5-35). The stages were Ia (n = 2), b (n = 4), IIa (n = 6), IIb (n = 8) and IIc (n = 4) according to ARCO staging system. The etiologies included corticosteroids (n = 16), alcohol abuse (n = 4) and idiopathic disease (n = 4). Magnetic resonance imaging (MRI) was used to measure lesion sizes with necrotic index method. And lesion locations were classified as medial, central and lateral.
  
  
  RESULTS
  The mean follow-up period was 40.3 (32-60) months. Among 7 painful hips, there were corticosteroids (n = 5) and alcohol abuse (n = 2). And 5 hips (20.8%) collapsed. The mean interval between diagnosis and symptom was 40 (36-48) months. The lesion locations were lateral-central (n = 4) lateral-central-medial (n = 3). Significant difference existed between the average necrotic index of symptomatic and asymptomatic hips (45.4% vs 32.7%).
  
  
  CONCLUSIONS
  There is a high risk of progression into symptomatic disease when the necrotic lesion occurs on the lateral and lateral-central or lateral-central-medial zone of the femoral head. Asymptomatic small and medially located lesions may be managed conservatively with close medical imaging observations.
authors.affiliation: Faculty of Electronic Information and Electronic Engineering, Dalian University of Technology, Dalian 116622, China.
authors.forename: Benjie
authors.initials: B
authors.lastname: Wang
authors.affiliation: Email: zhaodewei2000@163.com.
authors.forename: Dewei
authors.initials: D
authors.lastname: Zhao
authors.forename: Lin
authors.initials: L
authors.lastname: Guo
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Baoyi
authors.initials: B
authors.lastname: Liu
authors.forename: Weimin
authors.initials: W
authors.lastname: Fu
authors.forename: Hui
authors.initials: H
authors.lastname: Xie
mesh_terms: D000328:Adult; D018450:Disease Progression; D005260:Female; D005271:Femur Head Necrosis / Q000473:pathology*; D006615:Hip; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010020:Osteonecrosis / Q000473:pathology*; D055815:Young Adult