Is There Evidence for Aetiologically Distinct Subgroups of Idiopathic Congenital Talipes Equinovarus? A Case-Only Study and Pedigree Analysis

Background: Idiopathic congenital talipes equinovarus (CTEV) is a common developmental foot disorder, the aetiology of which remains largely unknown. Some aspects of the epidemiology suggest the possibility of aetiologically distinct subgroups. Previous studies consider CTEV as a homogenous entity which may conceal risk factors in particular subgroups. We investigate evidence for aetiologically distinct subgroups of CTEV. Methods: Parents of 785 probands completed a postal questionnaire. Family pedigrees were compiled by telephone. Case-only analysis was used to investigate interactions between risk factors and sex of the proband, CTEV laterality and CTEV family history. Results: The male∶female ratio was 2.3∶1, 58% of probands were affected bilaterally and 11% had a first-second degree family history. There were modest interactions between family history and twin births (multivariate case - only odds ratio [ORca] = 3.87, 95%CI 1.19–12.62) and family history and maternal use of folic acid supplements in early pregnancy (ORca = 0.62, 95%CI 0.38–1.01); and between sex of the proband and maternal alcohol consumption during pregnancy (female, positive history and alcohol consumed: ORca = 0.33, 95%CI 0.12–0.89). Previous reports of an interaction between maternal smoking and family history were not confirmed. Relatives of female probands were affected more often than relatives of male probands. Conclusions: These results provide tentative evidence for aetiologically distinct CTEV subgroups. They support the ‘Carter effect’, suggesting CTEV develops though a multifactorial threshold model with females requiring a higher risk factor ‘load’, and suggest areas where future aetiological investigation might focus. Large multi-centre studies are needed to further advance understanding of this common condition.