Syndactyly: Information on Fused Fingers and Toes

In medicine, syndactyly (ICD code: Q70.9) refers to a congenital malformation of the limbs. It is a subtype of dysmelia.

Syndactyly is characterized by the fusion of fingers or toes. Normally, the fingers and toes separate between the 5th and 7th weeks of embryonic development. In syndactyly, a developmental abnormality prevents this separation from occurring, causing the affected digits to continue growing together. 

The term syndactyly derives from Greek and consists of the terms “syn” (together) and “daktylos” (finger).

Syndactyly is one of the most common congenital malformations of the hands. One in 3,000 newborns is affected by simple syndactyly.

In cases of severe syndactyly, all the fingers on one hand may even fuse together. It is particularly common for the middle and ring fingers to be fused. The fusion of the fingers often results in restricted movement, such as when grasping objects with the hand.

On the foot, the second interdigital crease is frequently affected.

Medicine distinguishes between different forms of syndactyly. The number of fused finger or toe segments plays a role in this classification. In addition, a distinction is made between

• cutaneous syndactyly (from the Latin cutis—skin): There is only a skin connection between the digits
• osseous syndactyly (from the Latin *os*—bone): bone segments are fused together.
• In complex syndactyly, blood vessels and nerves are affected in addition to the skin and bones

In most cases, syndactyly of the toes does not cause any symptoms.

There are various causes for the fusion of fingers and toes. These include external factors affecting the baby during pregnancy, such as alcohol or certain medications. In amniotic band syndrome, firm rings of connective tissue form from the amniotic sac and constrict the fingers and toes.

Syndactyly is often associated with genetic syndromes, such as Apert syndrome or Carpenter syndrome. This is the case in 20 to 40% of affected children. In these cases, a genetic defect is responsible for the malformations. The condition is inherited in an autosomal dominant pattern. Syndactyly is a common symptom in children with genetically caused disorders involving physical developmental abnormalities. 

It is rare for the malformation to develop only in later stages of life. Medical professionals refer to this as exogenous syndactyly. The causes are usually poorly treated injuries and accidents. In these cases, the skin and bones were unable to heal properly.

The outwardly visible symptom of syndactyly is fused fingers or toes. This can limit the motor functions of the hands and feet.

In cases of severe syndactyly, even simple movements cannot be performed. This results in significant limitations in daily life.

As the hereditary condition progresses, bony connections form between the individual toes and fingers. If the fingers and toes vary in length, the medical term for this condition is acrosyndactyly.

Later, holes may appear in the skin bridge, posing a risk of painful inflammation.

The sense of touch and fine motor skills are also increasingly affected. The risk of complications is significantly higher in the hands than in the feet. Fused toes usually do not restrict the movements of those affected.

Children’s mental well-being can be severely affected by these malformations. Therefore, parents should work with their child to foster a positive outlook that supports their development.

The doctor usually detects syndactyly during a visual examination shortly after birth.

To diagnose the specific type of malformation, the doctor uses imaging techniques such as X-rays. This allows the doctor to precisely identify the bony bridges associated with osseous syndactyly.

Syndactyly can be successfully treated with early surgical intervention. The goal of the surgery is to achieve a good functional and aesthetic outcome.

During the procedure, the doctor separates the fused digits from one another. A decision must be made as to whether

• the skin bridge should simply be cut through or
• an additional skin graft from the groin area should be used to cover the separated fingers or toes.

Especially in children, it is crucial to avoid leaving large scars. Such scars would not grow with the child and could cause the fingers to become crooked due to the tension they exert.

The separation of syndactyly is complex and challenging and requires an experienced specialist in hand surgery.

Even more difficult is the treatment of the osseous, or bony, form of syndactyly. In this case, two digits share the same bony structure, which cannot be precisely identified. In addition, the surgeon must also be mindful of changes to blood vessels and nerves.

If syndactyly occurs in the toes, it is usually only a cosmetic issue. Those affected therefore experience no symptoms. For this reason, many people choose not to undergo surgery.

The principles of syndactyly treatment include gentle separation, skin grafting, and early rehabilitation. If your child is affected by syndactyly, there is no reason to panic. Once other conditions have been ruled out, surgery is usually sufficient to correct the deformity.

It is recommended that surgical correction be performed before the age of 3. This helps prevent joint deformities.

An experienced hand surgeon can make a precise diagnosis and develop a personalized treatment plan.