In this blog the ExpHand team will look at some of the causes of congenital hand differences. Our aim is to provide simple, helpful information on how and why these hand differences occur to the parents, friends, family members and carers of children born with them, and to promote understanding in general. You can find more of these informative pieces elsewhere on the ExpHand blog, including posts dealing with talking to children about limb difference, advice for new of a child with a limb difference, information on inclusive children's books and inclusive toys, and much more besides.
What are congenital hand differences (CHDs)? Congenital Hand Differences are hand differences that occur from birth where a child is born with a hand that is formed differently to what is commonly expected. The term "difference" is used rather than "abnormality" as this is what the child's hand is, different to others rather than abnormal. Congenital hand differences occur in approximately 1 in 2000 live births.
How do congenital hand differences happen?
Embryology is a branch of medicine and biology that studies how a foetus develops. Hands are formed between weeks 4 and 8 of a woman's pregnancy with webbing initially present between the digits which typically recedes by week 10. A network of signals are used by the foetus to work together to form the hand; and this happens in three directions to create a fully developed human hand. One of the most important regulators of this development is a protein called sonic hedgehog (SHH) - which really is named after the video game character. The amount of SHH the hand, and then the digits, receive determines the size and shape of them (1). If there is too much or too little SHH the hand can develop differently, resulting in a CHD.
Depending on where and when in the growth pathway signals differ, upper limb and / or hand development will be affected in different ways. It is not currently clear exactly why CHD's happen, but this may be due to genes "planning" foetal development in the womb or it could be environmental, depending on the womb itself or the external environment. However, most CHD's happen for unknown reasons that are not related to genes or the behaviour of parents, so remember - in the majority of cases, parents are not to blame for congenital hand differences happening.
What can we do about congenital hand differences?
There are a number of ways in which CHD's can be addressed, depending on the precise nature of the CHD itself. These include both surgical and non-surgical options too.
Surgery for congenital hand differences
As this page from NYU Langone Health shows, surgical treatment can be used to address syndactyly (fused fingers) and polydactyly (extra fingers). Depending on the severity of the condition and the age of the patient surgery may also be an option for people with Clubhand and Symbrachydactyly too. In most cases surgical treatment will require the involvement of a specialist orthopaedic and/or hand surgeon, and an overnight stay in hospital. It may well also require post surgery rehabilitation and ongoing therapy with other specialist caregivers, such as occupational therapists - but it's important to recognise that each case is different, and that each best case outcome (and the path to it) is different also.
Non surgical treatment for congenital hand differences
Occupational therapy and physiotherapy may help to treat a CHD even without surgery. Depending on the condition and it’s severity, the use of prosthetics may also be a viable treatment, and in the long term, therapeutic recreation is often also a good thing to do. What constitutes therapeutic recreation will vary from person to person but they can be identified as 'activities that a given person enjoys doing, or good habits that they pick up that happen to be good for their CHD'.
(1) Anderson, Eve, et al. “Human limb abnormalities caused by disruption of hedgehog signaling.” Trends in Genetics, vol. 28, no. 8, 2012, pp. 364–373., doi:10.1016/j.tig.2012.03.012. Web. 6 Mar. 2018.
Sheeba, Caroline J., et al. “Getting a handle on embryo limb development: Molecular interactions driving limb outgrowth and patterning.” Seminars in Cell & Developmental Biology, vol. 49, 2016, pp. 92–101., doi:10.1016/j.semcdb.2015.01.007. Web. 6 Mar. 2018.
Lettice, Laura A., et al. “The Conserved Sonic Hedgehog Limb Enhancer Consists of Discrete Functional Elements that Regulate Precise Spatial Expression.” Cell Reports, vol. 20, no. 6, 2017, pp. 1396–1408., doi:10.1016/j.celrep.2017.07.037. Web. 6 Mar. 2018.