Polydactyly

Polydactyly (less commonly called hyperdactyly) refers to the situation where there are more than the usual number of digits (five) in a hand or foot. It can be broadly classified as:

Estimated incidence is different for pre and post-axial polydactyly 6:

  • post-axial: ~1 in 3000
  • pre-axial: ~1 in 7000

Central polydactyly is the rarest encountered.

In addition, there may be a greater prevalence in individuals of African descent (particularly for post-axial polydactyly) 7.

A large proportion of polydactyly is isolated although they can be associated with an immense amount of anomalies which include:

If it is an isolated anomaly it is incidental and not of concern but if associated with another anomaly it then carries a vastly variable prognosis dependent on the rest of the syndrome.

Other than describing polydactyly based on the position of the accessory digit, it can also be described by the number of total digits e.g. hexadactyly (six digits), or even, heptadactyly (seven digits). Indeed the presence of seven individual digits is exceedingly rare but has been reported twice 8.

While radiology has little role in the diagnosis of polydactyly it is important in two ways:

  1. assessment of the remainder of the skeleton (if appropriate) for other skeletal anomalies, and as such aiding in the diagnosis on an underlying syndrome (which in turn may point to additional unsuspected anomalies, and allow for genetic counseling etc.)
  2. assess the local anatomy to aid in surgical planning. Of particular importance is the anatomy of the 'normal' digits and the relationship of the extra digit to the adjacent bones and joints.

The term "polydactyly" is derived from the Greek words "πολύς - polus" (many) and "δάκτυλος - daktulos" (finger).

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Article information

rID: 10844
Synonyms or Alternate Spellings:
  • Heptadactylism
  • Hexadactylism
  • Heptadactyly
  • Hexadactyly
  • Hyperdactyly
  • Polydactylism
  • Polydactylies
  • Polydactyly : general

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Cases and figures

  • Case 1: post axial
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  • Polydactyly
    Case 2: with tibial hemimelia
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  • original unedited...
    Case 3: pre axial
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  •  Case 4: ulnar dimelia
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  • Case 5: with Ellis-Van Creveld syndrome
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  • Case 6: antenatal ultrasound with trisomy 13
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  • Case 7: antenal ultrasound
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  • Case 8: pedal post-axial
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  • Frontal left hand...
    Case 9: Pallister-Hall syndrome
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  • Case 10: post-axial polydactyly
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