Definition

Syndactyly is a condition where a baby is born with fingers that are fused together or webbed, resembling the feet of a duck. Around half of children with this condition will have it on both hands. While it usually affects only the fingers, in some cases, it can also involve the toes.

In syndactyly, two or more fingers may be joined, with the most common fusion occurring between the middle and ring fingers. The fingers may be linked by a web of skin, or in some cases, they may appear to form a single finger due to the fusion.

This condition is relatively common, affecting about 1 in every 2,500 newborns, and is considered the most frequent congenital defect affecting the limbs.

Finger Involvement

• About 50% in the middle and ring fingers

• About 30% in the ring and little fingers

• About 15% in the index and middle fingers

• About 5% in the thumb and index fingers

Causes

The development of the upper limbs starts early in pregnancy. Typically, the development of the hands and feet involves the formation of webbing between the fingers and toes, giving them a structure that resembles webbed duck feet.

At about 6 weeks of gestation, the body sends a signal through specialized signaling proteins, one of the most important being called sonic hedgehog, to trigger the regression, or disappearance, of this webbing. This process, known as interdigital apoptosis, ensures that the fingers and toes develop their usual separate structure. When this regression process doesn't happen properly, the webbing remains, resulting in syndactyly. This failure of webbing to disappear is why humans generally do not have webbed fingers and toes.

Syndactyly often runs in families. Around 10-40% of children with this condition inherit it from one or both parents. In some instances, it may occur as part of a genetic syndrome, such as Poland syndrome, Apert syndrome, acrosyndactyly, or Carpenter syndrome.

Risk Factors

Syndactyly is more common in males than females.

Symptoms

The severity of syndactyly symptoms can vary depending on the specific type of syndactyly a child has. There are three primary types: simple, complex, and complicated.

• Simple syndactyly refers to cases where the fingers are fused by skin and soft tissue only.

• Complex syndactyly involves fusion of the bones within the fingers.

• Complicated syndactyly includes additional abnormalities in the bones, tendons, and ligaments.

In most instances, only the skin is fused, and the bones remain separate. Bone fusion is rare. Syndactyly can also be classified as complete or incomplete. In complete syndactyly, the skin is fused all the way to the fingertips. In incomplete syndactyly, the skin fusion does not extend all the way to the tips of the fingers.

Diagnosis

Syndactyly is usually identified at birth, although it may be spotted earlier during a prenatal ultrasound. A doctor can perform an X-ray to examine the structures of the child’s fingers and decide on an appropriate treatment. The doctor will also check the baby’s arms, shoulders, chest, legs, head, and face for any other abnormalities.

If other concerns arise, genetic testing and imaging of other body parts may be recommended to uncover any underlying syndromes or genetic issues.

Management

The primary treatment for syndactyly is surgery to separate the fused fingers. It is generally recommended that children undergo surgery between the ages of 1 and 2. For cases involving the index, middle, and ring fingers, surgery should typically be done before the child turns 2 years old. Early surgical intervention is crucial because it helps ensure the child has optimal hand function during the important years of motor skill development, both fine and gross.

If a child has syndactyly affecting the thumb or little finger, it is recommended that surgery to separate the fingers be performed within the first year of life. The thumb and little finger have distinct lengths compared to the neighboring fingers, and early separation helps the adjacent fingers develop more naturally and grow to their proper size.

Complex syndactyly should also be corrected before the age of 1. Early intervention can prevent deformities caused by bone fusion and allow for proper growth of the fingers.

During the surgery, the skin between the two fingers will be carefully separated. To cover the separated areas, the child may require a skin graft or a skin substitute. Typically, the graft will be taken from the elbow or wrist to minimize visible scarring.

To minimize complications, only one side of the webbed fingers is separated at a time. If multiple fingers are affected by syndactyly, more than one surgery may be necessary.

After surgery, the child will have a cast placed over their hand, forearm, and elbow for 2 to 3 weeks to immobilize the hand and protect the healing skin. Once the cast is removed, a splint will be worn for another 6 weeks to ensure that the fingers remain separated during the healing process.

The doctor may recommend occupational therapy to help reduce scar tissue formation, manage stiffness and swelling, and improve hand function.

Some children may experience "web creep" after surgery as they grow. This condition occurs when scar tissue forms in the spaces between the fingers, creating the appearance of recurrent syndactyly. Web creep is more likely if the fingers are separated before the child reaches 1 year of age. If this happens, a second surgery may be necessary.

Regular follow-up visits with the doctor are essential to ensure that the hand is healing correctly and that the fingers are moving as expected. In some cases, additional surgery may be needed to improve the hand’s function and appearance.

Complications

Some possible complications of syndactyly include:

• Web creep: This is the most frequent complication after surgery. Web creep is treated by reconstructing the web using a skin flap. Early web creep often results from the failure of a skin graft, while web creep that occurs during adolescence is typically caused by an imbalance between scar tissue and the surrounding skin during periods of rapid growth.

• Nail deformities: If left untreated, syndactyly can hinder finger development and hand function.

Prevention

Genetic conditions like syndactyly cannot be prevented during pregnancy. However, environmental factors, such as the following, can increase the likelihood of syndactyly and other genetic conditions:

• Alcohol consumption

• Smoking or using tobacco products

• Use of illegal drugs

Consult your doctor about foods, drinks, or activities to avoid while pregnant to reduce potential risks.

When to See a Doctor?

If you notice any changes in your baby's hands or feet, it is essential to consult a doctor. Additionally, after surgery, see the doctor if the child’s finger shows any of the following symptoms:

• Bleeding

• Discoloration

• Swelling

• Discharge

• Pain

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