Syndactyly | Symptoms & Causes

What are the different forms of syndactyly?

Comparison of Incomplete Syndactyly and Complete Syndactyly.

The classifications of syndactyly correspond to the condition’s different types and degrees of complexity. Syndactyly can be classified in the following ways:

  • incomplete: the webbing or joining doesn’t extend all the way to the fingertips
  • complete: the webbing or joining extends all the way to the fingertips
  • simple: the fingers are joined only by soft tissue
  • complex: the fingers are joined by bone or bony cartilage, as well as soft tissue, in a side-by-side fashion
  • complicated: the fingers are joined by bone or bony cartilage, as well as soft tissue, in a fashion other than side-by-side—such as with abnormally shaped, extra or missing bones

What are the causes of syndactyly?

During normal embryonic development (while the baby is still in the womb), the hand initially forms in the shape of a paddle; then — at about the sixth or seventh week of gestation — splits into separate fingers. Syndactyly results if there’s an irregularity in this process: The fingers fail to divide normally (failure of differentiation) and the result is a webbed hand.

Some cases of syndactyly occur in isolation and sporadically — meaning by themselves, for no identifiable genetic reason. In about 10 to 40 percent of cases, the condition occurs as an inherited trait. And in some cases, syndactyly is an accompanying defect in a genetic syndrome, such as Poland syndrome, Apert syndromeor Holt-Oram syndrome.

Syndactyly is visible at birth. It may also be visible in utero by fetal ultrasound.