In the early morning two baby boys were born at the nursery. Later that day the two sets of parents happened to meet in the nursery, one set of parents remarked how much their baby looked like his father and grandfather with his bald head and 7 fingers and 7 toes. After returning to their room, the other parents took a close look at their son’s fingers and toes only to discover that the small toe on the left foot had a double toe nail and a little extra width at the tip. These families demonstrate the variability and inheritance patterns that are associated with polydactyl.

From chance occurrence to documented genetic causes, polydactyly is associated with multiple diagnoses in humans, dogs, and cats.

What is polydactyly?

Polydactyly is congenital presence of extra tissue in the hands and/or feet. In our office at Rocky Mountain Pediatric OrthoONE we call them “fancy fingers”. Occasionally the polydactylous digit is completely formed and functional. More frequently it has incomplete structures and lacks typical motion. The extra digit is most common on the ulnar (little finger) side of the hand, less common on the radial (thumb) side. These are respectively known as postaxial (little finger), and preaxial (thumb) polydactyly.

Is polydactyly common?

The condition has an incidence of 1 in every 500 live births. The vast majority are simple and are passed from generation to generation within a family. Some of the children with more complicated forms of polydactyly may have other findings associated with a syndrome.

One study combined data from Alabama and Sweden. This study showed incidence of all types of polydactyly to be 2.3 per 1000 in white males, 0.6 per 1000 in white females, 13.5 per 1000 in black males, and 11.1 per 1000 in black females.[8]

What causes polydactyly?

Polydactyly can occur by itself or as one feature of a syndrome of congenital anomalies. When a single digit is involved it likely has no inheritance or genetic cause. When multiple digits are involved, a pattern of genetic cause is more likely. Generation to generation passage indicates a genetic component. Polydactyly can be influenced by a single gene or by a complex interaction of multiple genes.

How is polydactyly diagnosed?

The doctor will diagnose the extent of the condition based on a family history, medical history, and physical examination. If a child has a straight-forward family history of postaxial polydactyly no additional workup is necessary. If the child has a single duplicated thumb or isolated postaxial polydactyly and no other concerns noted by the pediatrician or specialist, then further workup will be unlikely. More complicated forms of polydactyly may require more complicated workups.

Medical history questions may include:

  • Have any other family members been born with extra fingers or toes?
  • Is there a known family history of any of the disorders linked to polydactyly?
  • Are there any other symptoms or problems?

How is polydactyly treated?

The pendulous postaxial extra digit with a narrow attachment to the hand can often be treated with a simple office procedure where either a suture or a clamp is placed at the base of the digit to disrupt the blood supply. The polydactylous digit then goes through a process similar to the umbilical cord as it shrivels, dries, and eventually falls off.

More complicated forms with boney attachment or wide bases usually require an operating room visit for surgical reconstruction. Ligament transfers may be needed to yield stability in the remaining digit. Radiographs are helpful as part of the pre-operative planning. Surgery is rarely scheduled before 6 months of age unless special circumstances exist.

Occasionally parents want to know whether removal is really required. Glove or shoe wear may prove to be challenging if the extra digit is preserved.

What is the long-term outlook for my child?

For most children a single reconstructive procedure yields a lifetime of good results. With the more complicated forms of polydactyly, long-term growth of the adjacent digit may be altered which could require additional surgical procedures.

Throughout their lives the two little boys born on the same day remained connected. One only needed a simple debulking and the other had several trips to the operating room. They played side by side on the play ground and the football field. For neither one was polydactyly an obstacle to a full and complete life.