Conditions Associated with Hitchhiker’s Thumb Instead, they said that the angles of people’s thumbs vary, with no clear division between hitchhiker and non-hitchhiker thumbs. An expert has argued that thumbs don’t fall into only two neat categories of hitchhiker’s thumb and non-hitchhiker’s thumb. But if one of your parents has the dominant allele for straight thumb, and the other has the recessive allele, you won’t have hitchhiker’s thumb.īut there has been some debate about the science behind hitchhiker’s thumb. This means that if both your parents have hitchhiker’s thumb, you should have it too. The trait from a recessive gene won’t show unless you have two copies, one from each parent. If the alleles are different, the recessive one is masked by the dominant allele, which means only the dominant trait shows. You receive one version of a gene, called an allele, from each of your parents. Their genes influence traits such as your height, eye color, blood type, and disease risk. Our genes contain information that specifies traits or characteristics that are passed down from your biological parents. Nearly 30% of participants from southern India had hitchhiker’s thumb. In a 2007 study of populations of different regions in India, hitchhiker’s thumb was found to be rarer in those from northern, western, and eastern India. Of those with hitchhiker’s thumb, 15.5% were male and 16.8% female. In 2011, researchers found that in a random sample of 310 people in Nigeria, 32.3% had hitchhiker’s thumb. The conclusion from this 1953 study was that hitchhiker’s thumb is a recessive trait.
They noted that many people had one hitchhiker’s thumb and one straight thumb. The researchers gave the name “hitchhiker’s thumb” to the thumbs that could bend at an angle equal to or greater than 50 degrees. A total of 450 families were studied.Ī protractor was used to measure the angle of people’s thumbs. But researchers say that it’s an inherited condition.Ī study published in 1953 was one of the first to analyze hitchhiker’s thumb. There haven’t been many studies carried out on hitchhiker’s thumb. Some people with hitchhiker’s thumb can bend this thumb joint backward as far as 90 degrees. The second bone starts at the knuckle and extends to the base of your thumb. The first bone starts at the tip of your thumb and extends to the knuckle. Unlike your fingers, which have three bones (phalanges), your thumb has only two bones. Hitchhiker’s thumb is not painful and does not make it harder to use your hands. The medical term for hitchhiker’s thumb is distal hyperextensibility. It is also known as Z-shaped deformity of the thumb. This means they bend backward beyond the typical range.
Some people have thumbs that are hypermobile.
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