title: Prognosis value of early diffusion MRI in Legg Perthes Calvé disease.
abstract: OBJECTIVE
  To evaluate diffusion MRI of the proximal femoral epiphysis and metaphysis as a prognosis factor in Legg Calvé Perthes (LCP) disease.
  
  
  METHODS
  Thirty-one children (mean age 5.5 years, range 2.5-10.5) with unilateral LCP were included in a prospective, consecutive series. Radiographs were analysed and classified as per Herring criteriae. Mean follow-up was 19 months (range 6-30). Forty-nine MRI scans were performed at either the condensation or fragmentation stage. Apparent Diffusion Coefficient (ADC) of both the femoral epiphysis and metaphysis were measured bilaterally and ADC ratio were calculated, then compared to the Herring group.
  
  
  RESULTS
  Sixteen hips were rated Herring A or B, 3 Herring B-C and 12 Herring C. ADC was increased in affected hips compared to unaffected sides, both at the femoral epiphysis (P<0.001) and metaphysis (P<0.0001). ADC ratio of the femoral metaphysis was positively correlated to Herring classification: if superior to 1.63, it was associated with a bad prognosis (Herring B-C or C) (P=0.0017, sensitivity=89%, specificity=58%). Interobserver reliability of ADC measurement was excellent. The 1.63 threshold could be determined as early as the condensation stage.
  
  
  CONCLUSIONS
  Diffusion presents several advantages including being non radiating and non invasive. It does not need contrast medium administration and it can be performed without anaesthesia. The origin of the increased ADC remains unknown. Basically, it reflects molecular changes (true diffusion) but it is also influenced by the vascular supply (pseudo-diffusion). ADC ratio could provide an early prognosis before Herring classification is applicable.
  
  
  METHODS
  Level III. Prospective uncontrolled study.
authors.affiliation: Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Baunin
authors.affiliation: Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: D
authors.initials: D
authors.lastname: Sanmartin-Viron
authors.affiliation: Department of Paediatric Orthopaedic Surgery, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France. Electronic address: faccadbled@wanadoo.fr.
authors.forename: F
authors.initials: F
authors.lastname: Accadbled
authors.affiliation: Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: N
authors.initials: N
authors.lastname: Sans
authors.affiliation: Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: J
authors.initials: J
authors.lastname: Vial
authors.affiliation: Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: D
authors.initials: D
authors.lastname: Labarre
authors.affiliation: Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Domenech
authors.affiliation: Department of Paediatric Orthopaedic Surgery, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
authors.forename: J
authors.initials: J
authors.lastname: Sales de Gauzy
mesh_terms: D002648:Child; D002675:Child, Preschool; D038524:Diffusion Magnetic Resonance Imaging; D042241:Early Diagnosis; D005260:Female; D005269:Femur / Q000473:pathology*; D005500:Follow-Up Studies; D006801:Humans; D007873:Legg-Calve-Perthes Disease / Q000175:diagnosis*; D008297:Male; D011379:Prognosis; D011446:Prospective Studies; D015203:Reproducibility of Results
keywords: Diffusion MRI; Hip osteochondritis; LCP disease; Pediatric hip