title: Legg-Calvé-Perthes disease and the risk of injuries requiring hospitalization: a register study involving 2579 patients.
abstract: OBJECTIVE
  Previous studies have suggested that Legg-Calvé-Perthes disease (LCPD) is associated with repetitive trauma, coagulation problems and anatomical abnormalities of the blood supply to the femoral head. The hypothesis that repetitive trauma can affect the blood supply of the femoral head, leading to LCPD, is supported by an animal model. For evidence of an increased risk of repetitive trauma, we investigated whether patients with LCPD have a higher risk for severe injuries requiring hospitalization.
  
  
  METHODS
  We identified 2579 patients with LCPD in Sweden during the period 1964-2005. 13,748 individuals without LCPD were randomly selected from the Swedish general population, matched by year of birth, sex and region (control group). Cox proportional hazard regression estimated the risks.
  
  
  RESULTS
  Compared to the control group, patients with LCPD had a modestly raised hazard ratio (HR) of 1.2 (95% CI 1.1-1.3) for injury requiring hospitalization. The risks were slightly higher for soft tissue injuries (HR = 1.3, 95% CI:1.1-1.4) than for fractures (HR = 1.1, 95% CI: 1.0-1.3) and more pronounced among females. Compared to the control group, the higher risk for injury only applied to the lower extremities (HR = 1.2, 95% CI: 1.0-1.4) in patients with LCPD.
  
  
  CONCLUSIONS
  Patients with LCPD are vulnerable to injuries which could be interpreted as a marker of hyperactive behavior. It could also implicate that anatomical changes in the bone formation or blood supply of the femoral head - increasing its sensibility for trauma - contribute to the etiology of LCPD.
authors.affiliation: Department of Orthopaedics, Uppsala University Hospital, Uppsala, Sweden. yasmin.hailer@surgsci.uu.se
authors.forename: Yasmin D
authors.initials: YD
authors.lastname: Hailer
authors.forename: Scott
authors.initials: S
authors.lastname: Montgomery
authors.forename: Anders
authors.initials: A
authors.lastname: Ekbom
authors.forename: Olof
authors.initials: O
authors.lastname: Nilsson
authors.forename: Shahram
authors.initials: S
authors.lastname: Bahmanyar
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D016022:Case-Control Studies; D016001:Confidence Intervals; D005260:Female; D050723:Fractures, Bone / Q000175:diagnosis / Q000453:epidemiology*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D015601:Injury Severity Score; D007873:Legg-Calve-Perthes Disease / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012016:Reference Values; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D017678:Sex Distribution; D017695:Soft Tissue Injuries / Q000175:diagnosis / Q000453:epidemiology*; D013548:Sweden; D014947:Wounds and Injuries / Q000175:diagnosis / Q000453:epidemiology