title: Relationship between bone marrow edema and development of symptoms in patients with osteonecrosis of the femoral head.
abstract: OBJECTIVE
  The purpose of this study was to determine the significance of risk factors on MR images for predicting the outcome of patients with osteonecrosis of the femoral head.
  
  
  METHODS
  Eighty-three asymptomatic or minimally symptomatic hips in 61 consecutive patients were followed up prospectively. Inclusion criteria included osteonecrosis of the femoral head identified by typical MRI findings, with no radiographic evidence of progression of collapse, and Harris hip score of 85 points or more. Every 3 months, the patients underwent clinical and radiographic examination, and MR images were obtained at 6- to 12-month intervals. Follow-up continued until worsening of hip pain with Harris hip score of less than 70 points or surgery. Asymptomatic hips were followed up for at least 24 months. The mean clinical and radiographic follow-up period after the initial diagnosis was 60 months (range, 3-168 months).
  
  
  RESULTS
  Thirty-six (43%) of the 83 hips were symptomatic at the last follow-up. Bone marrow edema was present in 28 hips (34%) during the follow-up period. Twenty-seven (96%) of the 28 hips were symptomatic, and bone marrow edema significantly correlated with worsening of hip pain (p < 0.0001). The necrotic volume of hips with bone marrow edema was significantly larger than those without bone marrow edema (p < 0.0001). Bone marrow edema was found to be the most significant risk factor for worsening of pain (p < 0.0001).
  
  
  CONCLUSIONS
  Bone marrow edema strongly correlated with necrotic volume and was the most significant risk factor for worsening of hip pain. A large necrotic volume of 30% or more may be the second useful indicator for predicting future worsening of hip pain.
authors.affiliation: Department of Orthopedic Surgery, Asahikawa Medical College, Midorigaoka Higashi 2-1-1-1, Asahikawa 078-8510, Japan. itobiro@asahikawa-med.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ito
authors.forename: Takeo
authors.initials: T
authors.lastname: Matsuno
authors.forename: Akio
authors.initials: A
authors.lastname: Minami
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001855:Bone Marrow Diseases / Q000209:etiology*; D004487:Edema / Q000209:etiology*; D005260:Female; D005271:Femur Head Necrosis / Q000150:complications* / Q000175:diagnosis*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors