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Concept
Polydactyly
Summary
Polydactyly or polydactylism (), also known as hyperdactyly, is an anomaly in humans and animals resulting in supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly (fewer fingers or toes).
As of 1977, the incidence of congenital deformities in newborns was approximately 2%, and 10% of these deformities involve the upper extremity.
In 1961, Frantz and O’Rahilly proposed, that congenital anomalies of the limb could be classified in seven categories, based on the embryonic failure causing the clinical presentation. These categories are failure of formation of parts, failure of differentiation, duplication, overgrowth, undergrowth, congenital constriction band syndrome, and generalized skeletal abnormalities. In 1976 this was modified by Swanson. Polydactyly belongs to the category of duplication.
As of 2009, research has shown that the majority of congenital anomalies occur during the 4-week embryologic period of rapid limb development.
As of 2002, polydactyly has been associated with 39 genetic mutations.
In humans/animals this condition can present itself on one or both hands or feet. The extra digit is usually a small piece of soft tissue that can be removed. Occasionally it contains bone without joints; rarely it may be a complete functioning digit. The extra digit is most common on the ulnar (little finger) side of the hand, less common on the radial (thumb) side, and very rarely within the middle three digits. These are respectively known as postaxial (little finger), preaxial (thumb), and central (ring, middle, index fingers) polydactyly. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist as a normal digit does.
Polydactyly can be divided into three major types, which are discussed below, which depend on the location of the additional digit.
In 2019 it was found that in cases of polydactyly with a fully functional additional digit, muscles to control the extra digit may be duplicated, resulting in increased motor control that allows the patient to carry out certain tasks with one hand that would normally require two.
Official source
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