Syndactyly (ICD code: Q70.9) is defined by doctors as a congenital malformation of limbs. It is a subtype of dysmelia.
Syndactyly is characterized by the fusion of fingers or toes . The fingers and toes normally separate between the 5th and 7th week of embryonic development. In syndactyly, there is a disorder so that the separation is not completed and the affected limbs continue to grow together.

Bones of the healthy developed hand © bilderzwerg / Fotolia
The term syndactyly comes from the Greek and consists of the terms "syn" (together) and "dactylos" (finger).
Syndactyly is one of the most common malformations of the hands. One in 3000 newborn children is affected by simple syndactyly.
In the case of severe syndactyly, all the fingers of a hand may even grow together. The middle and ring fingers grow together particularly frequently. The fusion of the fingers often results in restricted movement, for example when gripping with the hand.
On the foot, the second interdigital fold is often affected.
Medicine distinguishes between different forms of syndactyly. The number of fused finger or toe phalanges plays a role here. A distinction is also made between
- cutaneous syndactyly (from the Latin cutis - skin): There is only a skin connection between the limbs
- osseous syndactyly (from the Latin os - bone): Bone parts are fused together.

This illustration shows various forms of syndactyly on the fins of a hand © rumruay | AdobeStock
There are various causes of the fingers and toes growing together. These include external influences on the baby during pregnancy, such as alcohol or certain medications. In amniotic band syndrome, firm rings of connective tissue form from the egg membrane, constricting the fingers and toes.
In addition to these causes, syndactyly can also be inherited. This is the case in 20 to 40 % of affected children. In this case, a genetic defect is responsible for the malformations. The disease is inherited dominantly. Syndactyly is a common symptom in children with genetic diseases with physical developmental disorders. Affected children also suffer from Aarskog syndrome or Carpenter syndrome, for example.
It is rare for the malformation to develop later in life. Doctors then speak of exogenous syndactyly. The causes are usually poorly treated injuries and accidents. In these cases, the skin and bones are unable to heal properly.
The externally visible symptom of syndactyly is fused fingers or toes. This can restrict the motor functions of the hands and feet.
In the case of severe syndactyly, even simple movements cannot be performed. This results in considerable restrictions in everyday life.
As the hereditary disease progresses, bony connections develop between the individual toes and fingers. If the length of the fingers and toes varies, this is referred to in medicine as acrosyndactyly.
Later, holes appear in the skin bridge and there is a risk of painful inflammation.
The sense of touch and fine motor skills are also increasingly affected. The risk of complications is considerably higher on the hands than on the feet. Due to fused toes, those affected are usually not restricted in their movements.
The children's psyche can suffer greatly from the deformities. Parents should therefore train a positive and development-promoting perspective with their child.
The doctor usually recognizes syndactyly during a visual examination after birth.
To diagnose the particular form of malformation, the doctor uses imaging examination methods such as X-rays. This allows them to precisely determine the connecting bone bridges of the osseous syndactyly.
Syndactyly can be successfully treated with early surgery.
The doctor separates the fused limbs from each other. A decision must be made as to whether
- the skin bridge is simply severed or
- an additional skin graft from the groin region should cover the separated fingers or toes.
Especially in children, it is crucial not to leave any large scars. Such scars would not grow with the child and can lead to a curvature of the fingers due to their tension.
This surgical procedure is complex and demanding and requires an experienced specialist in hand surgery.
Even more difficult is the treatment of the osseous, i.e. bony, form of syndactyly. In this case, two limbs have the same bone structure, which cannot be precisely determined. The surgeon must also pay attention to changes in blood vessels and nerves.
If there is syndactyly on the toes of the foot, this is usually only an aesthetic problem. Those affected therefore have no symptoms. For this reason, many sufferers do not undergo surgery.

Toes that have grown together rarely cause discomfort. Surgery is therefore often not necessary © miramis art | AdobeStock
If your own child is affected by syndactyly, there is no need to panic. If other conditions can be ruled out, surgery is usually sufficient to correct the deformity.
It is advisable to perform the surgical correction before the age of 3. This prevents joint deformities.
An experienced hand surgeon can make a precise diagnosis and develop an individual treatment plan.