title: Evolution of femoral condylar ossification at MR imaging: frequency and patient age distribution.
abstract: OBJECTIVE
  To determine how the magnetic resonance (MR) signal intensity seen with variability in distal femoral epiphyseal ossification in children varies with (a) age, (b) sex, (c) distribution to the medial or lateral condyles, and (d) residual physeal cartilage.
  
  
  METHODS
  Ethics committee approval was obtained, and informed patient consent was waived. Two pediatric radiologists retrospectively reviewed the consecutive knee MR imaging studies of 910 children (457 boys, 453 girls; age range, 0.7-16.9 years) for variability in ossification and categorized the variability as preossification center, early ossification center, puzzle piece, incomplete puzzle piece, spiculation, or accessory ossification center. Patient age and sex, ossification variability site, residual physeal cartilage, and associated findings were analyzed. Basic descriptive statistical analysis, Student t tests for comparison of continuous variables, and κ statistics analysis of interobserver agreement were performed where appropriate.
  
  
  RESULTS
  In 202 (22.2%) patients (278 condyles), ossification variability was present. In the 910 patients, early ossification center (n = 172, 18.9%) and spiculated configuration of the secondary ossification center (n = 151, 16.6%) were the most common variants. Preossification center (50 [5.5%] patients), puzzle piece (26 [2.9%] patients), accessory ossification center (nine [1.0%] patients), and incomplete puzzle piece (two [0.2%] patients) were seen less often. Ossification variability was more common in the medial condyles (169 [18.6%] of 910 cases) than in the lateral condyles (109 [12.0%] of 910 cases), nearly always posteriorly located (277 [99.6%] of 278 condyles), and more common in boys (153/457 [33.5%]) than in girls (49/453 [10.8%]). Ossification variability was less common with decreasing residual physeal cartilage. Peak patient age ranges for ossification variability were 2-12 years for boys and 2-10 years for girls.
  
  
  CONCLUSIONS
  Ossification variability in the femoral condyles is common in children and should not be confused with abnormal processes.
authors.affiliation: Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, 9000 Gent, Belgium. lennartjans@hotmail.com
authors.forename: Lennart B O
authors.initials: LB
authors.lastname: Jans
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Jaremko
authors.forename: Michael
authors.initials: M
authors.lastname: Ditchfield
authors.forename: Koenraad L
authors.initials: KL
authors.lastname: Verstraete
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D004838:Epiphyses / Q000033:anatomy & histology* / Q000473:pathology; D005260:Female; D005269:Femur / Q000033:anatomy & histology* / Q000473:pathology; D019786:Gadolinium DTPA; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012016:Reference Values; D012189:Retrospective Studies; D012737:Sex Factors
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA