title: Increased risk of Blount disease in obese children and adolescents with vitamin D deficiency.
abstract: BACKGROUND
  Poor dietary habits and decreased outdoor activity has led to an epidemic of obese children and vitamin D deficiency. The lack of vitamin D alters bone development and mineralization by diminishing physiological levels of calcium and phosphorus. Given vitamin D's role in bone and growth plate mineralization and regulation, we hypothesized that vitamin D deficiency would lead to higher rates of fractures, slipped capital femoral epiphysis (SCFE), and Blount disease in obese youth.
  
  
  METHODS
  A retrospective review was performed at the obesity clinic using the obesity database (890 patients). Data obtained included body mass index (BMI), vitamin D levels (25-vitamin D), history of fractures, Blount disease, and/or SCFE. The chart review identified 2 populations of obese patients, those with vitamin D deficiency, <16 ng/mL (198 patients) and those not vitamin D deficient >16 ng/mL (692 patients). Fisher exact, χ², and 2-sample t tests along with logistic regression were used for statistical analysis. A P value ≤0.05 was considered statistically significant.
  
  
  RESULTS
  Blount disease was found to have a statistically significant (P<0.05) positive association with patient's sex, BMI, and vitamin D level. Specifically, males were 8.16 times more likely than females to be observed with Blount disease (P=0.01). Patients with very low vitamin D levels were 7.33 times more likely to have Blount disease than patients with higher levels (P=0.002). Each whole number increase in BMI increases the likelihood of Blount disease by 3% (P=0.01). There was no association between increased number of fractures or SCFE with vitamin D deficiency in these obese patients.
  
  
  CONCLUSIONS
  As our findings indicate, BMI and vitamin D levels have a strong association with Blount disease, which may be especially important among males. Ours is the first study to show a relationship between vitamin D deficiency and Blount disease, but further prospective studies are needed with larger numbers to confirm this independent association of vitamin D deficiency with Blount disease.
  
  
  METHODS
  Level III retrospective study.
authors.affiliation: Department of Pediatrics, University of Arkansas for Medical Sciences-Arkansas Children's Hospital, Little Rock, AR 72202, USA.
authors.forename: Corey O
authors.initials: CO
authors.lastname: Montgomery
authors.forename: Karen L
authors.initials: KL
authors.lastname: Young
authors.forename: Mark
authors.initials: M
authors.lastname: Austen
authors.forename: Chan-Hee
authors.initials: CH
authors.lastname: Jo
authors.forename: Robert Dale
authors.initials: RD
authors.lastname: Blasier
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ilyas
mesh_terms: D000293:Adolescent; D001848:Bone Diseases, Developmental / Q000209:etiology; D002648:Child; D004839:Epiphyses, Slipped / Q000209:etiology; D005260:Female; D005270:Femur Head; D050723:Fractures, Bone / Q000209:etiology; D006801:Humans; D008297:Male; D009765:Obesity / Q000150:complications*; D055034:Osteochondrosis / Q000151:congenital / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D014808:Vitamin D Deficiency / Q000150:complications*