Polydactyly is a congenital duplication within a limb. It occurs when more than five digits are present in the hand or foot. It may affect the whole digit or part of the digit.
Polydactlyly is the most common form of congenital upper limb anomaly. It can occur sporadically or in association with a number of syndromes. The underlying pathogenesis is likely to be disorganised segmentation of the limb bud during development.
Polydactyly can be subclassified according to site:
- radial polydactyly:
- involves the thumb
- previously termed preaxial polydactyly
- ulnar polydactyly:
- involves the little finger
- previously termed postaxial polydactyly
- central polydactyly:
- involves the index, middle and ring finger rays
- often observed in association with syndactyly
- mixed polydactyly: simultaneous radial and ulnar polydactyly
- crossed polydactyly: involvement of both hands and feet