Congenital hand differences
There are many types of congenital hand differences (preferred term for birth anomalies or defects). Most differences can be classified broadly as one of several categories: failure of formation or differentiation duplication overgrowth undergrowth constriction band syndrome or generalized anomalies and syndromes. I’ll discuss common congenital hand differences that most plastic surgeons and hand surgeons are familiar with.
Syndactyly or webbing of the fingers is a failure of differentiation. It can occur in 1 in 2000 live births and 10 times more common in Caucasians than African Americans. It most commonly affects the web between the long (middle) finger and ring finger but can affect any web space including between the toes. A family history is reported in about a third of cases. In most cases the procedure includes opening up the skin/soft tissue connections between the fingers and using a combination of skin flaps and skin grafts to resurfacing any raw areas and maintain the depth of the space between the fingers. In more complex cases there is fusion of the nail or bones that requires more extensive reconstruction. Unless many fingers are involved the surgery is usually performed at 18 to 24 months so the hand has time to grow to a size that is easier to manage. Operating earlier can pose a risk of injuring nerves and blood vessels to the fingers.
Clinodactyly is an abnormal angulation usually of the small finger and is considered a failure of differentiation. This is not usually painful but often limits motion of the finger. There is sometimes a small wedge of bone that causes the angulation. Surgery usually involves removing the abnormal bone or making a cut in the bone to change the angle of the finger.
Polydactyly is a duplication of one of the fingers. This is the most common congenital difference of the hand and usually involves the small finger. The incidence is 1 in 300 African Americans and 1 in 3000 Caucasians. Duplication has a strong association with prior family history. When the small finger is involved it is usually just a “nubbin” with a small skin bridge. In most cases removal can be done in the nursery under local anesthetic at the time a circumcision would be performed. Many people report having the extra digit “tied off” although this will likely leave a small bump that can be bothersome and rub on surfaces and cause irritation. Polydactyly of the thumb is less common and typically more complicated to reconstruct. It will often require repositioning of tendons and ligaments to produce a strong thumb. In these more complex cases the procedure should be done in the operating room and the child should be at least 6 months of age.
Thumb hypoplasia is an undergrowth of the first digit. This can be a significant disability – think of all the things you may need a thumb to do. This can range from just a slightly smaller thumb to in severe cases the complete absence of the thumb. Reconstruction is based on the level of disability. Minor forms often just require the web space between the thumb and index finger be deepened. In the most severe cases a thumb is “created” by rotating the index finger (called pollicization) and creating a 4-fingered hand. These surgeries are usually performed before the child develops a lot of compensations but after the hand has had time to grow.
Trigger thumb is not a “true” difference as above but is a hand problem that is common in childhood. This usually involves the thumb joint “catching” and preventing the thumb from straightening out. There is usually a nodule on the tendon that causes the triggering. Surgery is usually needed to release the point of constriction that is causing the tendon to trigger/lock. After this minor surgery the child typically gets full range of motion.
Congenital hand differences can be quite common. Early recognition and correction can vastly improve the quality of a child’s life. It is important to find a surgeon or specialist who has experience dealing with these differences. Most common problems can be corrected by a simple outpatient surgery but more complicated cases may require referral to a pediatric hand specialist.