Epidemiology
The condition has an estimated occurrence of 0.3–3.6 per 1000 live births. Postaxial hand polydactyly is most frequent in the United States in Black males. Preaxial polydactyly occurs in 0.08 to 1.4 in 1,000 live births. In the United States, it is more common in White people and also relatively frequent in Native American and Asian people. A 1994 study by Finley et al. combined data from Jefferson County, Alabama, United States, and Uppsala County, Sweden. This study found incidence of all types of polydactyly at rates of 2.3 per 1000 live births of White males, 0.6 per 1000 live births of White females, 13.5 per 1000 live births of Black males, and 11.1 per 1000 live births of Black females. Society and culture
People with polydactyly
Antonio Alfonseca, retired MLB professional baseball pitcher known as "El Pulpo" – Spanish for "the Octopus" with regard to his extra digit on each extremity. Endre Ady, Hungarian poet born with six fingers, but one was removed as a child. The poet later interpreted it as a sign of his selection (according to the ancient Hungarian belief, the táltos are born with more bones, such as six fingers). Brites de Almeida, a legendary Portuguese woman who killed seven hiding Castilian soldiers in her oven after the Battle of Aljubarrota, had six fingers on each hand. The actress Gemma Arterton was born with six fingers on each hand, the additional fingers being removed after birth. Anne Boleyn, former Queen of England, was rumoured to have six fingers on one hand.
The two-stage classification, according to Temtamy and McKusick, involves type A and B. In type A there is an extra little finger at the metacarpophalangeal joint, or more proximal including the carpometacarpal joint. The little finger can be hypoplastic or fully developed. Type B varies from a nubbin to an extra, non-functional little finger part on a pedicle. According to the three-type classification, type I includes nubbins or floating little fingers, type II includes duplications at the MCPJ, and type III includes duplications of the entire ray. Radial polydactyly
The Wassel classification is the most widely used classification of radial polydactyly, based upon the most proximal level of skeletal duplication. The most common type is Wassel 4 (about 50% of such duplications) followed by Wassel 2 (20%) and Wassel 6 (12%). Central polydactyly
The classification of central polydactyly is based on the extent of duplication and involves the following three types:
Type I is a central duplication, not attached to the adjacent finger by osseous or ligamentous attachments; it frequently does not include bones, joints, cartilage, or tendons. Type IIA is a nonsyndactylous duplication of a digit or part of a digit with normal components, and articulates with a broad or bifid metacarpal or phalanx. Type IIB is a syndactylous duplication of a digit or part of a digit with normal components, and articulates with a broad or bifid metacarpal or phalanx. Type III is a complete digital duplication, which has a well-formed duplicated metacarpal.