title: Hallux Valgus, By Nature or Nurture? A Twin Study.
abstract: To evaluate the contributions of shared but unmeasured genetic and environmental factors to hallux valgus (HV).
  
  
  
  Between 2011 and 2012, 74 monozygotic (MZ) and 56 dizygotic (DZ) female twin pairs self-reported HV and putative risk factors, including footwear use across their lifespan. Estimates of casewise concordance (PC), correlation (ρ), and odds ratios (ORs) were calculated, adjusting for age and other risk factors, and compared between MZ and DZ pairs using logistic regression, generalized estimating equations, and a maximum likelihood-based method, respectively.
  
  
  
  A total of 70 participants (27%) reported HV, with 12 MZ and 7 DZ pairs being concordant. After adjusting for age, twins were correlated (ρ = 0.27 [95% confidence interval (95% CI) 0.08, 0.46]) and concordant (PC= 0.45 [95% CI 0.29, 0.61]; mean age 58 years), with no difference between MZ and DZ pairs (P = 0.7). HV was associated with regularly wearing footwear with a constrictive toe-box during the fourth decade (adjusted OR 2.73 [95% CI 1.12, 6.67]). This risk factor was correlated in MZ (ρ = 0.38 [95% CI 0.15, 0.60]) but not DZ (ρ = -0.20 [95% CI -0.43, 0.03]) pairs. These correlations were significantly different (P = 0.002).
  
  
  
  Twins are correlated for HV, but we found no evidence that correlation was due to shared genetic factors. We identified an environmental risk factor, footwear with a constrictive toe-box, that is not shared to the same extent by MZ and DZ pairs, contrary to the assumption of the classic twin model. Footwear, and possibly genetic factors and unknown shared environmental factors, could contribute to developing HV.
authors.affiliation: La Trobe University, Melbourne, Victoria, Australia.
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Munteanu
authors.affiliation: La Trobe University, Melbourne, Victoria, Australia.
authors.forename: Hylton B
authors.initials: HB
authors.lastname: Menz
authors.affiliation: University of Melbourne and Royal Melbourne Hospital, Parkville, Victoria, Australia.
authors.forename: John D
authors.initials: JD
authors.lastname: Wark
authors.affiliation: University of Melbourne and Royal Melbourne Hospital, Parkville, Victoria, Australia.
authors.forename: Jemma J
authors.initials: JJ
authors.lastname: Christie
authors.affiliation: University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Scurrah
authors.affiliation: University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Minh
authors.initials: M
authors.lastname: Bui
authors.affiliation: La Trobe University, Melbourne, Victoria, Australia.
authors.forename: Bircan
authors.initials: B
authors.lastname: Erbas
authors.affiliation: University of Melbourne, Parkville, Victoria, Australia.
authors.forename: John L
authors.initials: JL
authors.lastname: Hopper
authors.affiliation: Monash University and Alfred Hospital, Melbourne, Victoria, Australia.
authors.forename: Anita E
authors.identifier: 0000-0001-8024-9049
authors.initials: AE
authors.lastname: Wluka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D059647:Gene-Environment Interaction; D006215:Hallux Valgus / Q000209:etiology / Q000235:genetics*; D006801:Humans; D016013:Likelihood Functions; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D012775:Shoes / Q000706:statistics & numerical data; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*; D014739:Victoria