Syndactyly Causes and Treatment

Syndactyly or webbed digits is a condition wherein two or more digits [[fingers in the hand or toes in the foot] ] are fused together.  Syndactyly can involve part or whole of the fingers. The joined finger may be joined just at the skin or could involve bones too.

The condition may occur in isolation or as a part of a genetic syndrome. There are over 300 genetic syndromes that involve syndactyly, such as Apert syndrome and Saethre-Chotzen syndrome.

Both genetic and environmental factors are responsible for this disease. It is familial in 0-40% of individuals.

It is the most common congenital malformation of the limbs. The occurrence is said to be  1 in 2000-3000 live births.

It is more common in Caucasians. Boys are more likely to have it than girls.

The treatment is often the surgical separation of digits and aims at providing functional digits.

Syndactyly can affect both hand digits and toes but because of being an advanced functional organ, syndactyly of hand is much more challenging.

In hand, the involvement of fingers, in decreasing order of frequency is as follows-

• Between the middle and ring fingers
• Little and ring fingers
• Middle and index fingers
• Thumb and index finger

Types of Syndactyly

There are many different forms of syndactyly and classified on the basis of severity of presentation.

• Cutaneous or Simple- Fingers joined only by soft tissue.
  • Simple incomplete – Partial union not extending to the fingertips
  • Simple complete – Whole finger is involved up to fingertips
• Complex – Bony or cartilaginous union
• Complicated – Syndactyly associated with a syndrome

Cause and Pathophysiology

Syndactyly can occur in isolation or as part of various syndromes. More than 300 syndromes have been ascribed but the most common are Apert’s, Poland, and constriction band syndrome.

Hereditary transmission can be autosomal dominant, autosomal recessive or X-linked recessive.

Syndactyly is a congenital deformity of the hand due to the failure of separation [type II congenital deformities of hand].

Thus most of thems form during the development of hand and arm.

The entire arm forms between 28 to 56 days of gestation. At about 40 days, all the fingers are webbed. These interconnections disappear before 56 days but a problem in signaling can lead to failure of separation.

In amniotic band syndrome or constriction band syndrome, the development of hands and fingers is normal but constriction band leads to scarring and the syndactyly.

Symbrachydactyly is a condition where the spectrum of presentation varies from almost normal fingers, short and completely webbed finger to no fingers at all.

Presentation

The patient may be seen soon after birth or later. At the first visit, the patient should be evaluated fo

• Type and severity of the disease
• Number  and extent of digits involved
• Length of the finger,
• The appearance of the fingernails

A photograph at the initial visit can be taken.

Often, photographing or drawing a picture of the hands during the initial visit is helpful

The following indicate a bony involvement al

• No passive motion between fingers
• The fusion of the fingernails
• A broad fingernail also may indicate a hidden polydactyly

If there is an anomaly of tendons, vessels, or nerves, it reflects complex syndactyly.

Functionally, the children with syndactyly function well but grabbing large or circular objects is a problem as fingers fail to open for a better grasp.

In older children, issues of self-esteem may arise because of the looks of the hand.

Imaging

Radiographs help to identify the severity of bony union and any other bony abnormalities.

Treatment

Surgery aims at dividing the finger, resurfacing the surgical wound with flaps, and full-thickness skin grafts and reconstruction of the web with dorsal fasciocutaneous flap.

Syndactyly that prevents full range of motion would require a surgical release. Minor syndactylies may be left unintervened.

The objective of surgery is to separate the fingers so that they can be spread normally to improve function and appearance.

Surgery can be done as early as 5 or 6 months of age though exact timing would depend on the fingers involved and the degree of severity.

While awaiting the appropriate age for surgery, parents are instructed to do massage and stretching exercises to widen the skin web between the digits and keep up a range of motion of the interphalangeal joints.

Early release can prevent malrotation and angulation. Malrotation and angulation is caused by differential growth rates of the involved fingers when the fingers are not separated.

When there are three digits involved,  one should stage the operations and separate the webbed fingers at different sessions, preferably at intervals of 3-6 months. This is done to avoid circulatory insult to the finger in the middle.

With any initial syndactyly release, only one side of the finger should be operated on at any given time to prevent ischemic compromise to the finger

Fasciocutaneous flaps, and full-thickness skin grafts are often needed to be used

Syndactyly involving border digits {ring-little, and thumb-index] should be done at less than 6 months as the difference in differential growth rates.

Middle-ring finger syndactyly can be released later as old as  2 years old as because middle and ring digits have similar growth rates

All releases should complete before school age.

Bilateral hand releases should be done simultaneously if the child is younger than 18 months. But if age is more, a staged procedure should be done because the child has become more active and it is difficult to restrain activity in both hands in older children.

Complications of the release include recurrence, finger ischemia, contracture, and skin-graft complications.

References

• Rayan GM, Upton J III. Syndactyly. Congenital Hand Anomalies and Associated Syndromes. Berlin: Springer-Verlag; 2014. 367-94.
• Percival NJ, Sykes PJ. Syndactyly: a review of the factors which influence surgical treatment. J Hand Surg Br. 1989 May. 14 (2):196-200. .
• Eaton CJ, Lister GD. Syndactyly. Hand Clin. 1990 Nov. 6 (4):555-75. .
• Jose RM, Timoney N, Vidyadharan R, Lester R. Syndactyly correction: an aesthetic reconstruction. J Hand Surg Eur Vol. 2010 Jul. 35 (6):446-50
• Lumenta DB, Kitzinger HB, Beck H, Frey M. Long-term outcomes of web creep, scar quality, and function after simple syndactyly surgical treatment. J Hand Surg Am. 2010 Aug. 35 (8):1323-9.
• Barot LR, Caplan HS. Early surgical intervention in Apert’s syndactyly. Plast Reconstr Surg. 1986 Feb. 77 (2):282-7.