What is polydactyly?

Polydactyly 3

Hand of a child with an extra digit next to their little finger.

Having an extra finger or toe is called polydactyly (pahl-ee-DAK-til-ee). The extra digit may range from a small, raised bump to a complete, working finger or toe. Most of the time, it’s smaller than the other digits and not well formed.

Sometimes the extra digit is only skin (a nubbin), and it connects to the hand or foot with only a narrow stalk of tissue. If the digit is better formed, it may have all the normal tissues, such as bone, muscles, blood vessels and nerves. In this case, it connects to the hand or foot deep inside.

Polydactyly is also called supernumerary digit. “Supernumerary” means “more than the normal number.”

  • There are 3 types of polydactyly based on where the digit is:

    • The extra digit is outside the thumb or big toe (preaxial polydactyly). When the digit is outside the thumb, it’s also called radial polydactyly. When it’s outside the big toe, it’s also called tibial polydactyly.
    • The extra digit is outside the little finger or little toe (postaxial polydactyly). When the digit is outside the little finger, it’s also called ulnar polydactyly. When it’s outside the little toe, it’s also called fibular polydactyly.
    • The extra digit is between other fingers or toes (central polydactyly).
  • This is a fairly common condition. It happens in about 1 in 1,000 babies. It’s passed down in some families (inherited). Often it happens to only 1 person in a family because of changes in their genes.

    Usually there’s an extra digit on only 1 hand or 1 foot. Some babies are born with an extra digit on both hands or both feet. Less often, babies are born with extra digits on both hands and both feet.

    Many babies with polydactyly have no other differences in their bodies and no health problems. But this condition can happen along with other hand or foot conditions, such as syndactyly (then it’s called polysyndactyly) or with other genetic conditions or syndromes.

Polydactyly at Seattle Children’s

Our doctors, surgeons and occupational therapists are experienced in the range of treatment options for polydactyly. Each year we see many babies with this condition in our clinics, and we create a tailored treatment plan for each of them to get the best results.

Polydactyly is among the most common congenital conditions treated by the experts in our Hand and Upper Extremity Program and our Foot and Ankle Deformities Program.

For many of our patients, treatment means surgery – sometimes highly complex surgery to remove a fully formed digit. Our surgeons are experienced at performing this type of surgery in children.

When needed, Rehabilitation Medicine provides occupational therapy to help children with polydactyly gain the best possible use of their hands or feet.

  • Within Orthopedics, your child is cared for by a team with vast experience, including pediatricians, pediatric orthopedic surgeonsnurse practitioners, physician assistants, nurses, athletic trainers, certified medical assistants, registered orthopedic technologists and sports physical therapists.

  • We have the largest group of board-certified pediatric radiologists in the Northwest. Our radiologists have special expertise using ultrasound to look for bone and joint changes so we can work with your child to help prevent future problems. If your child needs imaging that uses radiation, we use the lowest amount possible to produce the best image. We also have a 3D low-dose radiation X-ray machine, called the EOS, for safer full-body 3D images.

Symptoms of Polydactyly

Children with polydactyly are born with 1 or more extra fingers or toes.

The extra digit may be: 

  • A small, raised bump or a piece of skin that looks like a small finger or toe that isn’t fully formed (nubbin)
  • A complete, working finger or toe 

For some children, polydactyly is only 1 feature of a more complex genetic condition or syndrome. These children will have other signs and symptoms.

Diagnosing Polydactyly

If your child is born with an extra finger or toe, the doctor will examine your child carefully. During the exam, the doctor will check for other signs to tell whether your child has a more complex condition.

Your child may need an X-ray to see if there are bones in the extra digit and to see how the extra digit connects to the rest of the hand or foot. If the doctor thinks your child might have other genetic problems, your child might have tests to check their chromosomes.

Treatment Options for Polydactyly

In most cases, doctors remove an extra finger or toe in early childhood. The goal of treatment is to give your child a hand or foot that works well and looks typical. There are also practical concerns, such as removing an extra toe so your child’s foot fits well into shoes.

The method for removing an extra digit depends on how it connects to the hand or foot. An extra digit may connect with only a narrow stalk of tissue, or it may connect more deeply and share bones, muscles and other tissues with the hand or foot.

  • If the digit is poorly formed and contains no bone, sometimes the treatment is as simple as attaching a vascular clip at the base during a clinic visit. The clip stops blood flow to the digit so it will fall off, like the stump of the belly button does soon after birth. After attaching the clip, the doctor puts a bandage on your child’s hand or foot. In a couple of weeks, your child comes back to the clinic to have the bandage removed.

  • If the digit is more fully formed, a surgeon removes it in the operating room when your child is about 1 year old. This is done as a day surgery. Your child’s surgery will be based on their exact condition. More complex cases may require complex surgery. The surgery may involve carefully cutting through or around bones, ligaments, muscles, tendons and other tissues to remove the extra digit. Then the surgeon may need to move or reconnect some structures before closing the skin so the whole hand or foot works well and looks typical.

    After surgery, your child may need to wear a cast or splint on their hand or foot while it heals. The doctor will want your child to come back for follow-up visits to make sure they are healing well. Some children who have extensive surgery with cutting through many tissues may have occupational therapy to help with swelling, scarring and stiffness.

Contact Us

Contact Orthopedics and Sports Medicine at 206-987-2109 for an appointment, a second opinion or more information.

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