title: Unexpected MRI findings in clinically suspected Legg-Calvé-Perthes disease.
abstract: BACKGROUND
  In the setting of clinically suspected Legg-Calvé-Perthes (LCP) disease and negative/equivocal radiographs, contrast-enhanced MRI can be performed to confirm the diagnosis.
  
  
  OBJECTIVE
  To determine the frequency of unexpected causes of hip pain as identified by MRI in children with clinically suspected LCP disease and negative/equivocal radiographs.
  
  
  METHODS
  All pediatric contrast-enhanced MRI examinations of the pelvis and hips performed between January 2000 and February 2009 to evaluate for possible LCP disease in the setting of negative/equivocal radiographs were identified. MRI examinations performed to evaluate for secondary avascular necrosis were excluded. Imaging reports were retrospectively reviewed for unexpected clinically important causes of hip pain.
  
  
  RESULTS
  Thirty-six pediatric patients underwent contrast-enhanced MRI examinations for clinically suspected LCP disease in the setting of negative/equivocal radiographs. Twenty-two (61%) imaging studies were normal, while four (11%) imaging studies demonstrated findings consistent with LCP disease. Ten (28%) imaging studies revealed unexpected clinically important causes of hip pain, including nonspecific unilateral joint effusion and synovitis (n=7, juvenile chronic arthritis was eventually diagnosed in 3 patients), sacral fracture (n=1), apophyseal injury (n=1), and femoral head subluxation (n=1).
  
  
  CONCLUSIONS
  MRI frequently reveals unexpected clinically important causes of hip pain in children with suspected LCP disease and negative/equivocal radiographs.
authors.affiliation: Department of Radiology, Section of Pediatric Radiology, C.S. Mott Children's Hospital/F3503, University of Michigan Health System, 1500 E. Medical Center Drive, Ann Arbor, MI 48109-5252, USA.
authors.forename: Philip F
authors.initials: PF
authors.lastname: Lobert
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Dillman
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Strouse
authors.forename: Ramiro J
authors.initials: RJ
authors.lastname: Hernandez
mesh_terms: D000293:Adolescent; D002648:Child; D005188:False Negative Reactions; D005260:Female; D006621:Hip Joint / Q000473:pathology*; D006801:Humans; D007873:Legg-Calve-Perthes Disease / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D010146:Pain / Q000209:etiology*; D012189:Retrospective Studies