Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Polydactyly

Basics
Description
  • Polydactyly is a duplication of the fingers or toes that is detected at birth.
  • Classification:
    • Preaxial: Wassel classification:
      • I: Bifid distal phalanx
      • II: Duplicated distal phalanx
      • III: Bifid proximal phalanx
      • IV: Duplicated proximal phalanx
      • V: Bifid metacarpal
      • VI: Duplicated metacarpal
    • Central
    • Postaxial (involving small finger or toe):
      • Type A: Complete duplication with bony attachment to an adjacent digit
      • Type B: Rudimentary, incomplete duplication of the phalanges
  • Synonyms: Accessory digits, Split thumb
Epidemiology
  • Postaxial form occurs at a rate of 1 per 150 in African Americans versus 1 per 1,500 in Caucasians.
  • Preaxial form is more common in whites than in other races, and most cases are sporadic.
  • Central polydactyly is uncommon compared with border polydactyly.
  • No significant difference in reported occurrence between the genders
Risk Factors
African heritage is a risk factor.
 
Genetics
  • Postaxial polydactyly frequently is inherited as an autosomal dominant pattern but with variable penetrance.
  • Polydactyly of the index finger and polysyndactyly of the ring and long fingers probably are autosomal dominant conditions.
Etiology
The cause is unknown, unless the condition is associated with a syndrome.
 
Associated Conditions
  • Holt-Oram syndrome
  • Fanconi syndrome
  • Trisomy 13
  • Ellis-van Creveld syndrome
  • Grebe chondrodysplasia
Diagnosis
Signs and Symptoms
Duplicated fingers or toes
 
Physical Exam
  • Check for active and passive movement at each joint.
  • Assess the stability of the digit.
  • Look for an angular deformity at each joint.
  • Look at the skin coverage and webbing.
  • All these factors are important in determining surgical treatment.
Tests
Imaging
Plain film radiography of the hand is indicated.
 
Pathological Findings
The digits may vary in the extent of development of the phalanges and tendons.
 
Treatment
General Measures
  • Mild, type B postaxial polydactyly:
    • Treatment in the newborn:
      • Tie off the digit if it has no underlying skeletal connection.
      • In the presence of a skeletal connection, the extra digit should be electively removed surgically after 6 months of age.
    • This method is:
      • Safe
      • Not associated with bleeding complications
      • Associated with a satisfactory appearance
    • The rudimentary digit falls off in ~10 days.
  • Type A:
    • Requires operative ablation with transfer of any important parts to the adjacent finger.
    • Cosmetic concerns: Surgery is indicated to restore a normal appearance.
    • Polydactyly of the foot: Surgery often is needed to make normal shoe wear possible.
Surgery
Excision of the least developed digit, with preservation of the UCL and osteotomy, if indicated
 
Follow-up
Prognosis
  • Rudimentary, type-B postaxial polydactyly: Good
  • Other types of polydactyly (type A, duplicated thumb): Possible risk of angular growth of the adjoining digit or stiffness, but such problems rarely are symptomatic.
Complications
  • Small skin tag at the site of the polydactyly removal (rare)
  • Angular deformity possible after complex polydactyly reconstructions; possible deformity after thumb reconstruction
Patient Monitoring
For complex polydactyly, follow periodically with yearly checkups during growth.
 
Miscellaneous
Codes
ICD9-CM
  • 755.0 Polydactyly (general)
  • 755.01 Polydactyly (fingers)
  • 755.20 Polydactyly (toes)
Patient Teaching
Inform patients with complex or preaxial polydactyly about the possibility of angular deformity of the thumb during growth.
 
FAQ
Q: If 1 child is born with polydactyly, is there an increased risk of it occurring in additional children?
A: Postaxial polydactyly (ulnar side) frequently is inherited in an autosomal-dominant pattern, but it has a variable penetrance pattern.
 
Q: Is the treatment for ulnar and radial polydactyly the same?
A: No. Ulnar polydactyly frequently can be treated with surgical ablation, whereas a duplicated thumb most often requires a more technical reconstructive procedure with creation of a new ligament and possible osteotomy.

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