title: Assessment of Femoral Head Revascularization in Legg-Calvé-Perthes Disease Using Serial Perfusion MRI.
abstract: BACKGROUND
  Legg-Calvé-Perthes disease is a juvenile form of osteonecrosis of the femoral head. The purpose of this study was to use serial perfusion magnetic resonance imaging (MRI) to determine the pattern and rate of revascularization of the femoral heads of patients with the active stage of Legg-Calvé-Perthes disease.
  
  
  METHODS
  We performed a prospective study of 29 patients (30 hips) with a mean age (and standard deviation) of 8.4 ± 1.9 years who were diagnosed with Waldenström Stage-1 or 2 Legg-Calvé-Perthes disease. All patients had ≥2 perfusion MRIs, and 21 patients (22 hips) had ≥3. Perfusion percentages of the femoral epiphyses were measured by 2 independent observers. Statistical analyses included calculation of the intraclass correlation coefficient, the paired t test, the Mann-Whitney U test, and the Kruskal-Wallis test.
  
  
  RESULTS
  Initial perfusion MRIs showed the percent perfusion in the affected femoral heads to range from 5% to 70%. The average percent perfusion (and standard deviation) was 35% ± 16% on the first MRI, which increased to 77% ± 14% on the follow-up MRI acquired at an average of 10.5 ± 2.9 months later (p < 0.01). Serial assessment showed a general pattern of revascularization starting from the periphery of the posterior, lateral, and medial aspects of the femoral epiphysis and converging toward the anterocentral region. The average rate of revascularization was 4.9% ± 2.3% per month with a wide range among the patients (0.6% to 10.4% per month).
  
  
  CONCLUSIONS
  Revascularization of the necrotic femoral head increased over time in a horseshoe pattern, starting from the posterior, lateral, and medial aspects of the femoral epiphysis. The rate of revascularization was highly variable among patients.
  
  
  METHODS
  Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Center of Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, Dallas, Texas Harry.kim@tsrh.org.|Department of Orthopaedic Surgery, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Harry K W
authors.initials: HK
authors.lastname: Kim
authors.affiliation: Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois.
authors.forename: Jamie
authors.initials: J
authors.lastname: Burgess
authors.affiliation: Center of Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, Dallas, Texas.
authors.forename: Alec
authors.initials: A
authors.lastname: Thoveson
authors.affiliation: Center of Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, Dallas, Texas.
authors.forename: Paul
authors.initials: P
authors.lastname: Gudmundsson
authors.affiliation: Center of Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, Dallas, Texas.
authors.forename: Molly
authors.initials: M
authors.lastname: Dempsey
authors.affiliation: Center of Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, Dallas, Texas.
authors.forename: Chan-Hee
authors.initials: CH
authors.lastname: Jo
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D007873:Legg-Calve-Perthes Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D018919:Neovascularization, Physiologic / Q000502:physiology*; D011446:Prospective Studies; D013997:Time Factors