What is a Congenital Hand Difference? And How Does it Affect My Child Born with One?

January 29, 2025 / Diane Mabeley

What is a congenital hand difference?

If a baby is born with hands that are different than usual, the condition is called a “congenital hand difference”. These conditions happen while the baby is inside the womb and affect the hand’s form and function. The hand may have:1-5
  • Fewer fingers
  • Extra fingers
  • Joined fingers
  • Very short fingers
  • Extra-long fingers
  • Bent fingers or thumb
  • A central split
You may be upset that your child’s hand does not look or function as expected. You may find it hard to accept the differences, wonder if it is your fault, and worry about your child’s difficulties adapting in the future.
You are not alone. Worldwide, 5 in 10,000 babies have a congenital difference in the arm, hand, or fingers. Six in 100,000 are born missing a limb or hand. Three out of 4 children born without fingers are male.

This article will address these concerns, help you learn about different conditions, consider available treatments, and provide resources for more in-depth discussions.4,5


What did I do wrong and who can help?

First, you will be relieved to know that nothing you did or did not do caused your child’s condition. Hand differences can happen for no known reason. As far as science knows, only 1 in 10 of these children have a related gene (development instruction carrier).4

Second, you can get help from doctors specializing in treating hand differences. Hand surgeons spend an extra year after medical school and residency to complete a hand surgery fellowship and become experts. Hand therapists, who specialize in adaptation and strength-building, may also be part of a care team.

The goal of treatment is to enable the baby’s hand to work as well as possible.


How is the hand designed to work?

Understandably, you may want to learn all you can about your baby’s hand difference. A good place to start is to consider the structures and function of the hand.4

By design, your hands perform hundreds of highly complex tasks. Their 34 muscles, 27 bones, and over 100 tendons and ligaments work together in amazing ways. This includes everything from gripping, pinching, handwriting, and tying shoes to typing on a keyboard, playing a musical instrument, and much more.

These functions require complex interactions between the hand’s muscles, tendons, ligaments, bones, and the brain. The hand develops those structures and connections in the womb.1,4-6


How does the hand form in the womb?

Hand formation happens from about week 4 to week 8 in the womb. This process is called intrinsic development: processes inside the fetus direct it. Tiny code carriers (genes) and special molecules (proteins) control this process. The codes act like instructions that tell your body’s cells what to become and when. Some instructions cause structures to form, and other instructions cause formation to stop once that structure is complete.2,4,5


What are the types and causes of congenital hand differences?

Hand structure forms in a complex way and involves many intricate steps. This means that there are many opportunities along the path where something can go wrong. When that happens, the baby’s hand (or arm) forms differently than normal.4,5

Experts name these differences based on their effect on the hand.4
  • Malformation — something happens inside during the fetus’ development: Too many fingers, fingers too large or small, missing fingers, missing hand or limb. Most hand differences are malformations.
  • Deformation — something happens after the hand/limb forms: Amniotic bands around fingers, hands, or limbs can create a hand missing digits or a limb missing a hand.
  • Dysplasia — harmless growth appears on the hand and continues to grow after birth.
  • Syndromes — the hand differences are part of a set of whole-body differences affecting other structures. These may include the head, face, limbs, or organs.
Scientists are still studying the causes behind the various abnormal growth issues. The damage may be intrinsic (gene instructions fail inside the fetus). One theory proposes that a blood clot or problem in a blood vessel decreases blood flow to the limb. This lack of blood flow could stop growth.

Or the cause may be extrinsic (conditions in the womb damage the baby’s growth). In any case, you will want to obtain an accurate diagnosis of the child’s condition, including whether or not the cause is genetic. For this, you may consider genetic counseling – talking to a gene expert.4,5

Within those categories are the following groups of specific differences.

Syndactyly

Syndactyly (syn = together, dactyly = digit or finger) occurs when the fingers of the fetus’ hand do not separate in the womb. Instead, they have webbed tissue between them. This is the most common congenital hand difference, affecting about 1 in 2000 babies. Of all those born with syndactyly, fewer than 2 to 4 in 10 received a hand difference gene from a parent.1,3

Syndactyly occurs in 6 forms and can affect any of the fingers or the thumb:1,3,5
  • Radial syndactyly: The joining affects the thumb side and may cause the thumb to turn inward toward the palm.
  • Ulnar syndactyly: The joining affects the little finger side.
  • Simple syndactyly: The joining affects the soft tissue only.
  • Complex syndactyly: The joining involves bones and fingernails.
  • Incomplete syndactyly: The fingers are joined part way up the fingers.
  • Complete syndactyly: The fingers are joined to the tips.
Experts believe that syndactyly happens because a genetic message fails when the fetus is around 6 to 8 weeks old. A protein (growth factor) is supposed to cause the between-finger webbing to occur. Once the webbing is complete, special molecules send the signal to stop the growth (apoptosis). In syndactyly, the “stop forming webbing” message does not happen. So, the fingers do not separate.1,3

Symbrachydactyly is a more complex form of syndactyly: the fingers are short or absent and may be webbed.

Polydactyly

Polydactyly (poly = many; dactyly = finger or digit) happens when the hand grows extra fingers or thumbs. It occurs in as many as 1 in 3000 births. The hand’s bone arrangement determines the type of polydactyly, named according to which bone(s) are extra.1

The hand has 3 kinds of bones, any of which can be duplicated to create polydactyly: fingers (phalanges), palm bones (metacarpals), and wrist bones (carpals). The finger and wrist bones can be close to (proximal) or farther from (distal) the palm bones. The extra hand bones can be partly joined (partial) or fully joined (complete). Finally, the joined bones can be on the thumb side of the hand (radial), the central part of the hand (central), or the little finger side of the hand (ulnar).1,4

Camptodactyly

Camptodactyly (campto = bent; dactyly = finger or digit) occurs when the joint between the lower finger and the upper finger (interphalangeal joint) is bent. Camptodactyly conditions involve the finger’s middle joint 29 percent of the time, most often that of the little finger.1,4

Experts believe that camptodactyly happens because the underlying tissue (fascia) or finger tendon is too tight.

Clinodactyly

Clinodactyly (clino = curve or bend; dactyly = finger or digit) occurs when the little finger curves left or right at the middle joint. The bone itself grows in a curve instead of straight. This condition seldom causes pain or functional difficulties.1,4

Pediatric trigger thumb

Pediatric trigger thumb is one of the most common hand differences. It occurs in about 3 in 1000 births. Normally, the thumb structure bends and extends by a special tendon going through a tunnel on the palm side of the thumb base. Experts believe that pediatric trigger thumb happens because the tendon is too thick to go through the tunnel. This causes the thumb to either get stuck in the bent position or make a clicking noise when bending.4

Cleft hand

Cleft hand (central longitudinal deficiency) is when the center part of the hand is partially or completely split from top to bottom. Sometimes it is part of a syndrome involving other body parts or organs. Scientists believe that special cells on the outer edge of the fetus’ limb bud (ectoderm) direct hand formation. In cleft hand, the genes that instruct these cells to grow do not do their job.1


What are our treatment options?

At first, you may find facing your child’s condition to be overwhelming. You probably did not know about the difference before their arrival. Suddenly, you are swept into a world of new medical terms, complicated facts, and treatment decisions.5,6

It is normal to be upset, worried, and even angry that this has happened. Do not hesitate to share your concerns with your care team and family. Together, you can learn about the condition and treatment options, think through care choices, and make treatment decisions. Shared decision-making including your medical team and you leads to the best outcomes.5,6

Depending on the details of the child’s situation, there are several options:
  • Surgical procedures to separate webbed fingers, remove extra fingers, rebuild parts of the hand, add strength or length to an arm or finger, or even move skin or digits around
  • Non-surgical procedures like hand therapy, use of orthoses (to align a joint or finger in a better position), and use of adaptive devices (tools to help the child accomplish certain tasks)


How do I decide whether to have surgery or not?

For many parents, it is scary to consider their child undergoing surgery. As with any surgery, there are risks as well as benefits to consider. There are things that surgery can accomplish, and things that it cannot. Arm yourself with information, and you will become more confident while facing these important decisions.5,6

If a child needs surgery while they are a baby or toddler, the caretaker will be deciding without their input. If a child can wait until closer to age 8 for surgery, they may have the ability to share the decision-making.5,6 However, many of the procedures have better outcomes if they are done at a younger age.

Fortunately, there are expert surgeons and anesthesiologists highly trained and skilled in children’s hand surgery. These specialists follow strict guidelines to protect the child.5,6

And remember, the goals of any treatment are to maximize the hand’s function and normalize its appearance.6


Types and purposes of hand surgery

As we have said, there are many types of hand surgery to treat the many types of hand differences. Some result in better outcomes at a younger age, correcting issues before the first year of rapid development. Other procedures provide the most help at later ages when the hand structures are more mature. Your doctor will discuss the optimal timing with you.5,6

Surgical procedures fall into several categories:6
  • Skin flaps and grafts
  • Transfers
  • Straightening
  • Lengthening

Skin flaps and grafts
  • Because it is a living organ, skin can be surgically cut and shaped. To repair syndactyly, for example, surgeons often cut flaps of skin and rearrange them to separate fused fingers. A special flap called a “z-plasty” can widen the web area between fingers and release stiff skin (contracture).6
  • A graft entails taking skin from one place on the body and using it to cover an open area that needs skin to close. The surgeon can take the skin graft from any part of the body with extra skin, matching color and type as closely as possible.6
Webbing release
  • Syndactyly involves joined or webbed fingers. To separate the fingers, the surgeon can cut skin flaps and use grafts as described above. If the fusion involves bones, they may have to transfer bone from another part of the body to create a bone for the boneless freed finger. (see Partial and complete toe transfer, below). They may even separate fingernails. Once the fingers are apart and the open areas are covered, the surgeon stitches the skin closed using a special surgical thread (suture).6
Digit or arm lengthening
  • Short fingers may need lengthening to improve pinching and gripping — 2 important hand functions. The surgeon can place a set of pins and a bar into the bone, with the bar coming through the skin. Every day, the parents give the bar a tiny (millimeter) turn to slowly lengthen the bone. Or the surgeon can transfer bone from the hip, knee, or toe to the short bone.6
Partial and full toe bone transfer
  • Symbrachydactyly (sym = joined; brach = short; dactyly = finger or digit) is when a child’s fingers are not fully formed or just nubbins. To provide the stubby finger with bone, the surgeon can transfer one bone to the nubbin and secure it with a wire and cast.6
  • If a child is born without usable fingers, the surgeon can transfer one or more complete toes to the hand. This surgery requires a microscope so that the surgeon can see and preserve all the tiny parts of the toe (blood vessels, nerves, tendons, ligaments, bone, and skin layers) needed for it to function after the transfer.6
Finger transfer on the same hand
  • If a child is born without a thumb or a non-bending thumb, the surgeon can shift the index finger to the thumb position (pollicization). For children born with a cleft hand, surgery can move the hand’s fingers to fill in the gap.6
Straightening surgery
  • Although complex, it is possible to straighten curved fingers. The key consideration is whether the surgery will help the child to pinch and grasp. The surgeon will break the bone, set it in its proper position, and allow it to heal with a wire or pin. The bandage or cast holds the pin until the skin and bone heal, after which the pin is removed.6
For a more detailed description of the types of hand surgery used to repair hand differences, please see Chapter 6: “Hand Surgery: Indications and Techniques” in The Hand Book: An Informational Guide for Parents of Children With Hand Differences.6


What about quality of life?

Studies have examined the quality of life of children with congenital limb differences. In one such study, the researchers captured facts about the children’s level of functioning, pain, emotional/mental health, and peer relationships. For children less than 11 years old, the parents answered the surveys; children 11 years old and older answered for themselves.2

The results showed that despite their limb differences, children functioned well, were emotionally and mentally healthy, and had good social relationships with their peers. Children scored more poorly when they had limb differences on both sides (bilateral) and additional physical differences. In any case, despite the stress of living with a hand difference, these children adapted successfully.2


Final thoughts: your child’s future

Your child’s treatment should improve their hand’s form and function — that is the goal. But a child is more than their hand. They are a whole person, possessing emotions, physical and mental abilities, hopes, and dreams. How their hand difference affects them will depend largely on how their caretaker(s) handle it. As the child grows, and as you support them emotionally, they can learn coping strategies to deal with their reality. Above all, the hope is that they learn to accept their hand difference and face their world with confidence.4,5 


This blog was reviewed by a certified hand surgeon for accuracy.

 
 
  1. Goldfarb C. Congenital hand differences. J Hand Surg Am. 2009; 34(7):1351-1356. doi.org/10.1016/j.jhsa.2009.06.014
  2. Bae DS, Canizares MF, Miller PE, Waters PM, Goldfarb CA. Functional Impact of Congenital Hand Differences: Early Results From the Congenital Upper Limb Differences (CoULD) Registry. J Hand Surg Am. 2018;43(4):321-330. doi:10.1016/j.jhsa.2017.10.006
  3. Bhatt RA. What is Syndactyly? Hand Care: The Upper Extremity Expert. American Society for Surgery of the Hand Website. https://www.assh.org/handcare/blog/what-is-syndactyly. Updated October 5, 2020. Accessed January 14, 2025.
  4. Lightdale-Miric N, Tuberty S. Hand Questions: Understanding What Causes Hand Differences (and What Doesn’t). In: The Hand Book: An Informational Guide for Parents of Children With Hand Differences. Chicago, IL: American Society for Surgery of the Hand. 2022:25-37. Available at https://assh.box.com/s/0w08ih5r3q10vc4tdsndrl53wte2xkkk. Accessed January 15, 2025.
  5. Congenital Hand Differences. Hand Care: The Upper Extremity Expert. American Society for Surgery of the Hand Website. https://www.assh.org/handcare/condition/congenital-hand-differences. Updated November 2022. Accessed January 13, 2025.
  6. Lightdale-Miric N, Tuberty S. Hand Surgery: Indications and Techniques. In: The Hand Book: An Informational Guide for Parents of Children With Hand Differences. Chicago, IL:American Society for Surgery of the Hand. 2022:61-73. Available at https://assh.box.com/s/nz56oubmxl0lquniclzlapvkljbm700d. Accessed January 15, 2025.
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