Although clubfoot is one of the most common congenital abnormalities affecting the lower limb, it remains a challenge not only to understand its genetic origins but also to provide effective long-term treatment. This review provides an update on the etiology of clubfoot as well as current treatment strategies. Understanding the exact genetic etiology of clubfoot may eventually be helpful in determining both prognosis and the selection of appropriate treatment methods in individual patients. The primary treatment goal is to provide long-term correction with a foot that is fully functional and pain-free. To achieve this, a combination of approaches that applies the strengths of several methods (Ponseti method and French method) may be needed. Avoidance of extensive soft-tissue release operations in the primary treatment should be a priority, and the use of surgery for clubfoot correction should be limited to an “a la carte” mode and only after failed conservative methods. Level of Evidence: Level V, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Update on clubfoot: etiology and treatment.

Clubfoot affects 1 in 1000 live births, although little is known about its genetic or developmental basis. We recently identified a missense mutation in the PITX1 bicoid homeodomain transcription factor in a family with a spectrum of lower extremity abnormalities, including clubfoot. Because the E130K mutation reduced PITX1 activity, we hypothesized that PITX1 haploinsufficiency could also cause clubfoot. Using copy number analysis, we identified a 241 kb chromosome 5q31 microdeletion involving PITX1 in a patient with isolated familial clubfoot. The PITX1 deletion segregated with autosomal dominant clubfoot over three generations. To study the role of PITX1 haploinsufficiency in clubfoot pathogenesis, we began to breed Pitx1 knockout mice. Although Pitx1+/− mice were previously reported to be normal, clubfoot was observed in 20 of 225 Pitx1+/− mice, resulting in an 8.9% penetrance. Clubfoot was unilateral in 16 of the 20 affected Pitx1+/− mice, with the right and left limbs equally affected, in contrast to right-sided predominant hindlimb abnormalities previously noted with complete loss of Pitx1. Peroneal artery hypoplasia occurred in the clubfoot limb and corresponded spatially with small lateral muscle compartments. Tibial and fibular bone volumes were also reduced. Skeletal muscle gene expression was significantly reduced in Pitx1−/− E12.5 hindlimb buds compared with the wild-type, suggesting that muscle hypoplasia was due to abnormal early muscle development and not disuse atrophy. Our morphological data suggest that PITX1 haploinsufficiency may cause a developmental field defect preferentially affecting the lateral lower leg, a theory that accounts for similar findings in human clubfoot.

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Pitx1 haploinsufficiency causes clubfoot in humans and a clubfoot-like phenotype in mice

Also known as clubfoot, idiopathic congenital talipes equinovarus (ICTEV) is the most common pediatric deformity and occurs in 1 in every 1000 live births. Even though it has been widely researched, the etiology of ICTEV remains poorly understood and is often described as being based on a multifactorial genesis. Genetic and environmental factors seem to have a major role in the development of this disease. Thus, the aim of this review is to analyze the available literature to document the current evidence on ICTEV etiology. The literature on ICTEV etiology was systematically reviewed using the following inclusion criteria: studies of any level of evidence, reporting clinical or preclinical results, published in the last 20 years (1998–2018), and dealing with the etiology of ICTEV. A total of 48 articles were included. ICTEV etiology is still controversial. Several hypotheses have been researched, but none of them are decisive. Emerging evidence suggests a role of several pathways and gene families associated with limb development (HOX family; PITX1-TBX4), the apoptotic pathway (caspases), and muscle contractile protein (troponin and tropomyosin), but a major candidate gene has still not been identified. Strong recent evidence emerging from twin studies confirmed major roles of genetics and the environment in the disease pathogenesis. The available literature on the etiology of ICTEV presents major limitations in terms of great heterogeneity and a lack of high-profile studies. Although many studies focus on the genetic background of the disease, there is lack of consensus on one or multiple targets. Genetics and smoking seem to be strongly associated with ICTEV etiology, but more studies are needed to understand the complex and multifactorial genesis of this common congenital lower-limb disease.

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The etiology of idiopathic congenital talipes equinovarus: a systematic review.

Background: Congenital talipes equinovarus (CTEV) is a common developmental disorder of the foot, affecting between 1 and 4.5 babies per 1000 live births. The etiology is not well elucidated. While both genetic and environmental factors are implicated, no specific genes have been identified and little is known about environmental risk factors. Methods: We conducted a case-control study of idiopathic congenital talipes equinovarus (ICTEV) in the United Kingdom. 194 cases and 60 controls were recruited. Pedigrees were obtained for 162 cases. Results: The rank of the index pregnancy, maternal education and cesarean delivery were significantly associated with ICTEV risk in a multivariate model. There were suggestions that maternal use of folic acid supplements in the three months before the pregnancy decreased ICTEV risk, and that parental smoking during the pregnancy increased risk. One quarter of pedigrees showed a family history of CTEV, and autosomal dominant inheritance was suggested in some of these. Conclusion: Uterine restriction did not appear to have a strong influence on ICTEV development in our study. Large population-based studies are needed to clarify the etiology of this common developmental disorder.

Pedigree analysis and epidemiological features of idiopathic congenital talipes equinovarus in the united kingdom: a case-control study

Congenital talipes equinovarus (CTEV) is a common developmental disorder of the foot, affecting between 1 and 4.5 per 1000 live births. The aetiology is not well elucidated. While both genetic and environmental factors are implicated, no specific genes have been identified and little is known about environmental risk factors. We conducted a case-control study of idiopathic congenital talipes equinovarus (ICTEV) in the United Kingdom. 194 cases and 60 controls were recruited. Pedigrees were obtained for 167 cases. The rank of the index pregnancy, maternal education and caesarean delivery were significantly associated with ICTEV risk in a multivariate model. There were suggestions that maternal use of folic acid supplements in the three months before the pregnancy decreased ICTEV risk, and that parental smoking during the pregnancy increased risk, although the associations were not statistically significant. One quarter of pedigrees showed a family history of CTEV, and autosomal dominant inheritance was suggested in some of these. Uterine restriction did not appear to have a strong influence on ICTEV development in our study. Large population-based studies are needed to clarify the aetiology of this common developmental disorder.

/pdf/pedigree-analysis-and-epidemiological-features-of-idiopathic-3gg5xkt6yw.pdf

Pedigree analysis and epidemiological features of idiopathic congenital talipes equinovarus in the United Kingdom: a case-control study

Worldwide, 1-4 per 1,000 births are affected by clubfoot. Clubfoot etiology is unclear, but both genetic and environmental factors are thought to be involved. Low folate status in pregnant women has been implicated in several congenital malformations, and folate metabolism may be affected by polymorphisms in the methylenetetrahydrofolate reductase gene (MTHFR). Using a case-parent-triad design, the authors investigated whether the MTHFR C677T polymorphism, and maternal periconceptional folic acid supplement use, influenced risk of isolated clubfoot. Three hundred seventy-five United Kingdom case-parent triads were recruited in 1998-1999. Among the children, there was a significant trend of decreasing clubfoot risk with increasing number of T alleles: relative risk for CT vs. CC = 0.75, 95% confidence interval: 0.57, 0.97; relative risk for TT vs. CC = 0.57, 95% confidence interval: 0.35, 0.91; p trend = 0.006. This association was not modified by maternal folic acid use. Maternal MTHFR genotype did not influence clubfoot risk for the offspring overall, although a possible interaction with folic acid use was found. This is the first known report of a specific genetic polymorphism associated with clubfoot. The direction of the association is intriguing and suggests that DNA synthesis may be relevant in clubfoot development. However, clubfoot mechanisms are poorly understood, and the folate metabolism pathway is complex. Further research is needed to elucidate these relations.

The C677T Polymorphism in the Methylenetetrahydrofolate Reductase Gene (MTHFR), Maternal Use of Folic Acid Supplements, and Risk of Isolated Clubfoot: A Case-Parent-Triad Analysis

Introduction: Between 1 and 4 per 1000 births worldwide are affected by clubfoot. Clubfoot etiology is unclear, but both genetic and environmental factors are thought to be involved. Low folate status in pregnant women has been implicated in several congenital malformations and folate metabolism may be affected by polymorphisms in the MTHFR gene. Methods: Using a case-parent triad design, we investigated whether the MTHFR C677T polymorphism, and maternal peri-conceptional folic acid supplement use, influenced risk of isolated clubfoot. 375 case-parent triads took part. Results: Among children there was a significant trend of decreasing clubfoot risk with increasing number of Talleles: relative risk (RR ) CT vs CC=0.75 (95% CI: 0.57,0.97); RR TT vs CC=0.57 (95% CI: 0.37,0.91); p trend=0.006. This association was not modified by maternal folic acid use. Conclusion: Maternal MTHFR genotype did not influence risk of clubfoot in the offspring overall, although a possible interaction with folic acid use was found. This is the first report of a specific genetic polymorphism associated with clubfoot. The direction of the association is intriguing and suggests DNA synthesis may be relevant in clubfoot development. However, clubfoot mechanisms are poorly understood and the folate metabolism pathway is complex. Further research is needed to elucidate these relationships.

The c677t polymorphism in the methylenetetrahydrofolate reductase gene (mthfr), maternal use of folic acid supplements and risk of isolated clubfoot: a caseparent triad analysis

Gross similarities between the external appearance of the hind limbs of the peroneal muscle atrophy (pma) mouse mutant and congenital talipes equinovarus (CTEV), a human disorder historically referred to as ‘clubfoot’, suggested that this mutant could be a useful model. We used micro-magnetic resonance imaging to visualize the detailed anatomy of the hind limb defect in mutant pma mice and performed 3D comparisons between mutant and wild-type hind limbs. We found that the pma foot demonstrates supination (i.e. adduction and inversion of the mid foot and fore foot together with plantar flexion of the ankle and toes) and that the tibiale and distal tarsals display 3D abnormalities in positioning. The size and shape of the tibia, fibula, tarsal and metatarsal bones are similar to the wild-type. Hypoplasia of the muscles in the antero-lateral (peroneal) compartment was also demonstrated. The resemblance of these features to those seen in CTEV suggests that the pma mouse is a possibly useful model for the human condition. To understand how the observed deformities in the pma mouse hind foot arise during embryonic development, we followed the process of foot rotation in both wild-type and pma mutant mice. Rotation of the hind foot in mouse embryos of wild-type strains (CD-1 and C57/Black) occurs from embryonic day 14.5 onwards with rotation in C57/Black taking longer. In embryos from both strains, rotation of the right hind foot more commonly precedes rotation of the left. In pma mutants, the initiation of rotation is often delayed and rotation is slower and does not reach completion. If the usefulness of the pma mutant as a model is confirmed, then these findings on pma mouse embryos, when extrapolated to humans, would support a long-standing hypothesis that CTEV is due to the failure of completion of the normal process of rotation and angulation, historically known as the ‘arrested development hypothesis’.

Londale Madrigal

Papers

The C677T Polymorphism in the Methylenetetrahydrofolate Reductase Gene (MTHFR), Maternal Use of Folic Acid Supplements, and Risk of Isolated Clubfoot: A Case-Parent-Triad Analysis

The c677t polymorphism in the methylenetetrahydrofolate reductase gene (mthfr), maternal use of folic acid supplements and risk of isolated clubfoot: a caseparent triad analysis

Micro-magnetic resonance imaging and embryological analysis of wild-type and pma mutant mice with clubfoot