Syndactyly means joined fingers. This definition also applies to toes. It is about a frequent congenital abnormality which is caused by a separation defect of the digit radius.
In the embryo, the hand has the shape of a blade. The cartilaginous union which will later turn into phalanges is previously separated in 5 digit radius, but everything is covered by embryologic tissue (future skin).
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The tissue between fingers is meant to disappear. This normal “programmed cell death” process is called apoptosis. An alteration in the apoptosis results in the persistence of the skin between two or more fingers: this is the most frequent type of syndactyly: skin syndactyly. With lesser frequency, it is about an embryologic cartilaginous union abnormality. Two or more cartilaginous radius is joined, which results in fusions between the phalanges of two adjacent fingers; this is called the complex type of an osseous syndactyly.
Syndactyly may be hereditary –there are similar cases in the family -; however, depending on the type of transmission, syndactyly may skip generations.
In other cases, it is about a first familial case. Sometimes, it is said to be an external influence which prevented the separation of the fingers at the beginning of the pregnancy period. Many factors may influence on apoptosis between the 4th and 6th week of embryologic development (viral disease, medications, pelvic radiographs..) However, no evident cause is usually found.
Diagnosis is simple when the new born baby is inspected. The level of syndactyly is determined: partial, to the third or half length of the fingers, that is, more distal or complete.
Fingernails are most often separated, but they may be joined. Joint mobility and possible finger deviation are examined.
In clinical practice, a simple hand anterior radiograph is taken when the baby is born or mainly at the age of 6 months. This x-ray allows eliminating bony union.
Exceptionally, in case of complex hereditary abnormalities, the surgeon will prescribe a renal or cardiac scan, and guide the family towards some genetic advice.
Fingers are surgically separated (surgical release). The age and type of operation depends on the location and severity of syndactyly. Basically, for the skin syndactyly, located at the central fingers (most common case), surgical release may be carried out at the age of 18 months. For partial syndactyly, we utilise Z plasty/ an original plastic technique in the shape of a trident which allows a perfect and lasting release without resorting to skin grafts.
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In case of the 1st webspace syndactyly, between the thumb and the index finger, or in case of bony union, an early release before the age of 1 is proposed.
Surgical post-operative is usually simple. Fingers scar in 2 to 3 weeks. Dressings are replaced each 3 days.
The follow-up must be made for several years, as the finger growth may sometimes involve a small surgical correction (webspaces operated on with a skin graft may migrate distally as growth occurs).
