Polydactyly, the name that classifies the condition of having more than 5 fingers on a single hand or more than 5 toes on a single foot, is condition usually recognized at birth. The condition is traditionally hereditary and in most cases can be visualized by the presence of an extra digit at the time of delivery. As we’ll discuss, there are varying types of accessory (extra) digits with some types non-visible and only discovered with x-rays of the foot sometime later in life.
In most cases, polydactyly is a cosmetic anomaly and presents no immediate pain or health concerns for the patient. The most involved digits are the “postaxial” digits: those digits located towards the outside of the foot. They are referred to as the “postaxial” digits relative to their position during prenatal growth, but in terms of treatment and management, this designation means very little. In half of those who are diagnosed with polydactyly, the extra digit will be present bilaterally; meaning on both feet, such that the patient may be born with 12 toes. The demographic most associated with polydactyly are African-Americans, but the diagnosis is not exclusive to that population.
As mentioned above, there are varying types of accessory digits and they are so classified according to which bones in the foot are duplicated, contributing to the extra digits presence. In addition, the classification also notes the shape of the metatarsal (long bones in the foot) and how it has accommodated to allow for the extra toe. Keep in mind when trying to understand this classification system that each digit (2-5) is made up of one metatarsal and 3 smaller bones referred to as phalanges. As Podiatrists, we typically classify into 5 categories:
Normal metatarsal with duplication of two of the three phalangeal bones, contributes to the presence of two toes, neither with the correct number of bones to create a completely “normal extra digit.”
Wide (Block) metatarsal whereby the metatarsal is widened but not duplicated. The widened portion of the metatarsal accommodates for duplication of all three phalangeal bones, yielding two “normal” toes.
Y-shaped metatarsal. Rather than the metatarsal widening, the portion of the metatarsal bone closest to the toes splits, forming a y-shaped bone. Again, this allows for duplication of all three phalangeal bones and the presence of two “normal” toes.
T-shaped metatarsal. This is much the same as the y-shaped metatarsal, but rather than looking like a “y,” the metatarsal bone looks more like a “t,” still allowing for duplication of all three phalange bones and the creation of two “normal toes” versus the traditional one.
Complete duplication is present when the metatarsal bone and all three phalangeal bones are duplicated, such that a single foot has 6 metatarsal bones (versus the traditional 5) and 17 phalangeal bones (versus the traditional 14).
Now that you’re an expert at the polydactyly classification system, and would be able to diagnose any x-ray where extra digits were present (just kidding!), lets briefly discuss how it’s treated! As mentioned above, polydactyly presents no immediate pain or health concerns to the patient, but it can complicate issues of self-confidence and present an annoyance when attempting to buy shoes. Therefore, if present at birth, the extra toe is usually removed at birth and never mentioned again. However, if it is not removed at birth or if an incomplete form of polydactyly is present where an extra digit isn’t noticed at the time of birth but extra bones are present within the foot, the extra bones may be dealt with later in life.
When polydactyly occurs your Podiatrist must first evaluate your foot with x-rays to determine which of the 2 copies of a single toe has the most potential for normal growth. Once they’ve identified which of the two will grow most normally, they will address the copy of that digit and usually opt for amputation. Amputation is a scary word and can often be associated with massive infections and commonly as a diabetic complication, but here, if the patient is in good health otherwise, amputation will be tolerated quite well. Since there is already and extra digit present, when removed, it should not affect function of the foot, and the normal amount of toes remain!
Although we hope that each new baby is born with only 10 fingers and 10 toes, if presented with a newborn that fashions 11 toes, we will know how to treat him/her!