title: Factors related to progression of thoracolumbar kyphosis in children with achondroplasia: a retrospective cohort study of forty-eight children treated in a comprehensive orthopaedic center.
abstract: METHODS
  Retrospective cohort.
  
  
  OBJECTIVE
  To assess the period prevalence and predisposing factors in thoracolumbar kyphosis progression (TLK).
  
  
  BACKGROUND
  TLK is a common presentation in children with achondroplasia. This condition occurs very early in life; it is observed during the first attempts to sit, and has multifactorial etiology. Studies are limited on the radiologic assessment of the angle of wedging of the deformed vertebra, but none to our knowledge on TLK progression in achondroplasia.
  
  
  METHODS
  The records of 48 of 103 children with achondroplasia seen between 1997 and 2005 were examined. Developmental motor delay (DMD) and other potential predictors of TLK were assessed. The criteria for DMD were a child's inability to sit without support by 6 months and an inability to walk independently by 15 months. Lateral radiographs were examined for the magnitude of TLK, thoracic kyphosis, lumbar lordosis, percentage of apical vertebral wedging for the height and width of the vertebra, and apical vertebral translation. The association between TLK progression and potential predisposing factors were assessed using chi test, Fisher exact, t test, and binomial regression model for predictor identification.
  
  
  RESULTS
  The period prevalence of TLK progression in children with achondroplasia was 35.4%. TLK progression was significantly related to DMD, risk ratio = 2.40, 95% confidence interval = 1.10 to 5.58, apical vertebral translation (P = 0.01), and percentage apical vertebral wedging for height (P = 0.01). After adjustment for relevant covariates, the relationship between DMD and TLK progression persisted, risk ratio = 2.65, 95% confidence interval, 1.20 to 5.91.
  
  
  CONCLUSIONS
  DMD was significantly associated with TLK progression and other radiologic parameters namely, initial TLK of >25 degrees , percentage of apical vertebral wedging for the height of the vertebra, and apical vertebral translation.
authors.affiliation: Department of Orthopaedics, Alfred I duPont Hospital for Children, Wilmington, DE 19803, USA.
authors.forename: Battugs
authors.initials: B
authors.lastname: Borkhuu
authors.forename: Durga K
authors.initials: DK
authors.lastname: Nagaraju
authors.forename: Gilbert
authors.initials: G
authors.lastname: Chan
authors.forename: Larry
authors.initials: L
authors.lastname: Holmes
authors.forename: William G
authors.initials: WG
authors.lastname: Mackenzie
mesh_terms: D000130:Achondroplasia / Q000150:complications* / Q000601:surgery; D016009:Chi-Square Distribution; D002648:Child; D015331:Cohort Studies; D002658:Developmental Disabilities / Q000175:diagnosis / Q000209:etiology; D018450:Disease Progression; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000150:complications / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D015999:Multivariate Analysis; D019637:Orthopedic Procedures; D011859:Radiography; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*