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Polydactyly and Syndactyly

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    Skeletal     dysplasia
    Polydactyly     and     syndactyly


Introduction Antenatal Postnatal West Midlands Data



Syndactyly is the fusion or reduction of adjacent digits, more common between toes than fingers. The extent of this fusion varies from a fusion of the soft tissues only (cutaneous syndactyly) to fusion of the bone (synostosis or osseous syndactyly). Syndactyly can be isolated or occur as part of a syndrome such as acrocephalosyndactyly (e.g. Apert syndrome) or triploidy. Some families are affected by an autosomal dominant isolated syndactyly. A severe form is lobster claw or split hand/foot syndrome (ectrodactyly).

Polydactyly is the presence of extra digits on the hands or feet. The extent can vary from a fleshy protrusion to complete duplication of a digit. Polydactyly can be isolated; an autosomal dominant form exists in some families, or occur as part of a syndrome such as short rib-polydactyly syndrome. There are many sub-classifications of this anomaly but the two major subgroups are preaxial and postaxial. Pre-axial polydactyly occurs on the side of the thumb or big toe. Post-axial polydactyly is relatively more common and occurs on the side of the little finger or lateral side the foot and in association with trisomy 13.

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Syndactyly and polydactyly are potentially both visible on ultrasound, although good views depend both upon the position of the fetus and the volume of liquor, with reduced liquor severely limiting the ability to see the extremities well. The best view to detect these anomalies is by examining a fully splayed hand but this may not always be possible. Plantar views of the foot or a section across the hand in axial plane may be diagnostic. Because both defects occur as part of other syndromes, the detection by ultrasound of syndactyly or polydactyly should be followed by a detailed scan for other malformations.

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The cosmetic and functional outcomes for syndactyly depend on the extent of the skeletal anomaly. If the digits are normal, separation with skin grafts takes place in childhood, however if a short finger is distorting a long finger earlier surgical intervention may be necessary. If other skeletal anomalies are present, separation should only be undertaken if a good functional result can be achieved.

Simple fleshy additional digits can be excised early providing a good cosmetic outcome. If the digit is fixed with tendons, the hand or foot must be adequately grown to allow dissection and reconstruction without affecting the growth or function of the remaining digits.

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To be added

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© Perinatal Institute 2011