title: Femur shaft fracture at a young age and the risk of subsequent severe injuries during childhood: a cohort study.
abstract: BACKGROUND
  A child who suffers a fracture or a soft-tissue injury at a young age faces an increased risk of subsequent injuries during childhood. This risk could be related to personal and family characteristics or to lower-than-average bone-mineral density. The purpose of this nationwide cohort study was to estimate the association between a femur shaft fracture at a young age and the subsequent risk of hospitalization for injuries during childhood.
  
  
  METHODS
  We compared the subsequent risk of hospitalization for injuries during childhood among 1,404 children (exposed) who were one to three years of age when they suffered a femur shaft fracture with the risk among 13,814 randomly selected, gender- and age-matched femur fracture-free children (unexposed). Hazard ratios (HRs) and 95% confidence intervals (CIs) for severe injuries defined as fractures or soft-tissue injuries requiring hospital admission were estimated in a Cox proportional hazards model.
  
  
  RESULTS
  Exposed children exhibited no significantly increased risk of upper-extremity fractures or soft-tissue injuries during childhood, regardless of sex and follow-up time. Boys exhibited a 162% increased risk of suffering a lower leg fracture requiring hospital admission (HR?=?2.62, 95% CI: 1.45-4.71), but the refracture risk was not significant for girls 2.02 (0.58-6.97).
  
  
  CONCLUSIONS
  We found an increased risk for subsequent fractures in the lower leg that requires inpatient care during childhood for boys, but not for girls, who were one to three years of age when they first suffered a femur shaft fracture. This increased fracture risk is probably not simply the result of greater risk-taking among boys. The explanation might relate to factors affecting the bone quality of the lower leg.
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, SE 171 77, Stockholm, Sweden. Johan.von.heideken@ki.se.
authors.forename: Johan
authors.initials: J
authors.lastname: von Heideken
authors.forename: Tobias
authors.initials: T
authors.lastname: Svensson
authors.forename: Maura
authors.initials: M
authors.lastname: Iversen
authors.forename: Anders
authors.initials: A
authors.lastname: Ekbom
authors.forename: Per-Mats
authors.initials: PM
authors.lastname: Janarv
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005264:Femoral Fractures / Q000150:complications / Q000453:epidemiology*; D050723:Fractures, Bone / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D007223:Infant; D015601:Injury Severity Score; D008297:Male; D012307:Risk Factors; D017678:Sex Distribution; D014947:Wounds and Injuries / Q000453:epidemiology* / Q000209:etiology