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Bone, Joint and Muscle Conditions



What Is Polydactyly?

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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. 

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

  • The extra digit is outside the thumb or big toe (pre-axial 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 (post-axial 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).

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

Polydactyly in Children

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

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 one person in a family because of changes in their genes.

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

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Our doctors, surgeons and occupational therapists are well versed 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 one of 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.

Should your child see a doctor?

Find out by selecting your child’s symptom or health condition in the list below:

Summer 2014: Good Growing Newsletter

In This Issue

  • Understanding the Power and Influence of Role Models
  • Legal Marijuana Means Greater Poisoning Risks for Children
  • Why Choose Pediatric Emergency Care?

Download Summer 2014 (PDF)