Babies born with hands that are different than the normal hand have a
congenital hand difference.
The upper limb is formed between four and eight weeks after the sperm
and egg unite to form an embryo. The embryo develops an arm bud at four
weeks. The tip of the arm bud sends messages to each cell as the upper
limb forms. Millions of steps are followed to form a normal arm. Failure
of any of these steps to occur can result in a congenital hand
difference. Research continues into further understanding of this
embryonic process. Some congenital hand differences may occur due to a
genetic cause. Many congenital hand differences just occur without an
One in twenty children is born with some difference from normal,
either major or minor. The different groups of congenital hand
differences include missing parts of the arm (failure of formation),
webbed or fused parts of the hand (failures of separation), extra parts
present in the hand (duplication), undergrowth or overgrowth of parts of
the hand, or constriction band syndrome.
The most common congenital hand difference in the Caucasian
population is webbed fingers (syndactyly - see Figure 1). The most
common congenital hand difference in the black population is an extra,
sixth digit on the little finger side (post-axial polydactyly - see
Figure 2). The most common congenital hand difference in the Asian
population is an extra thumb (thumb polydactyly - see Figure 3).
Because there are so many different congenital hand differences, it
is important that your child be evaluated by a hand surgery specialist
to help determine if any treatment is needed. Some congenital hand
differences are associated with genetic disorders or other medical
problems. Your hand specialist may request further genetic evaluation by
a geneticist, or may request further medical testing by your
pediatrician or family physician.
Immediately after the birth of a child with a a congenital
abnormality, the patents may feel shock, anger and guilt. These are
normal emotions. All the dreams of a perfect baby did not take place.
Each family member must cope with their feelings. Rarely is there
anything parents or doctors could have done differently.
Your newborn doesn’t realize that he or she is different. The
baby has all the normal needs of any newborn. The way the baby has
formed is normal for him or her, without pain and without a sense of
loss. Talk to your physician about support groups or professional
All babies born with congenital hand differences should be evaluated
by a hand specialist to make an individual assessment of the type.
Depending on the type of congenital hand difference, treatment may be
recommended. For example, webbed fingers are surgically separated. Extra
digits can be surgically removed with reconstruction of the remaining
digit if necessary. Hand function can be improved if the functions of
thumb pinch or finger grasp is compromised. Some congenital hand
differences may need therapy to help improve hand function. In some
cases, no intervention is necessary.
Figure 1: Syndactyly between long and ring fingers
Figure 2: Polydactyly, with an extra little
Figure 3: Thumb polydactyly, with duplication of the
© 2006 American Society for Surgery of the Hand