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Extra fingers or thumb: Polydactyly

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Polydactyly is one of the most common malformations of the hand.

In the polydactyly of the hand, there are more than four fingers or more than one thumb. It can occur in the thumb side (called preaxial polydactyly or duplication of the thumb), in the little finger side (called postaxial polydactyly) or central fingers (central polydactyly). Preaxial polydactyly is more common in Caucasians and postaxial in the black. Central polydactyly is uncommon.

Extra small finger (postaxial polydactyly)

Postaxial polydactyly in white individuals, unlike black race, is rare and may be indicative of an underlying syndrome (send these children to the pediatrician and geneticist). It is usually hereditary.

The extra digit can be fully developed as a standard finger (type A) (Figure 18) or be rudimentary and pediculated (type B, in the form of a ball hanging from the little finger) (Figure 19).


Figure 18. Polydactyly of the little finger, type A. Fully formed finger.



Figure 19A. Polydactyly of the little finger, type B. Rudimentary sphere-shaped finger, attached by a pedicle to the hand.

Type B can be treated after birth in the outpatient office, by a ligature (strangulation with a wire or staple) (Figure 19B).


Figure 20. Strangulation of the extra rudimentary little finger, with a mini-staple.

Type A requires surgical treatment. Surgery is not simply “cut the extra digit”, a joint reconstruction is necessary to avoid deflection of the finger in the future. This alteration is operated at around the first year of life.

Extra thumb (thumb duplication or preaxial polydactyly)

Duplication of the thumb (preaxial polydactyly) is not usually inherited, generally affects only one hand, and is not associated to other malformations. It is therefore not necessary to send the child to the pediatrician or geneticist.

The thumb is divided at a variable level (from the tip to the base of the thumb, Wassel classification). Most often it is divided at the level of the "knuckle" (Figure 20).


Figure 20A. Duplicated thumb at the base of the thumb level: Wassel type IV.

falta 20B

Figure 20B. Radiography, which shows that the cleavage occurs at the level of the first phalanx (first and second phalanges duplicated).

Surgery is not simply “cut the extra digit”, a joint reconstruction is necessary to avoid deflection of the finger in the future. This anomaly is operated at around the first year of life, when the child begins to do the thumb pinch.


Figure 20C. The thumb has been rebuilt, repositioning ligaments and muscles of the thumb. The needle is held 3 weeks while they heal.

A special case is the mirror hand (ulnar dimeliae). Read section.

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