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POLYDACTYLY

Introduction

Polydactyly is the most common congenital hand anomaly. It is characterized by the presence of an extra digit, but due to great heterogeneity in polydactyly presentation, not all cases involve a complete digital duplication. Polydactyly can occur on the radial side, ulnar side, or involve non-border digits, and each subset has its own characteristic ethnic and genetic predilections. The deformity typically occurs in isolation, but it may also develop in association with one or more syndromic malformations. Surgical treatment is directed toward creating a functional and aesthetically satisfactory hand, and largely depends on the type and severity of polydactyly.1,2,3

Pathophysiology

  • Polydactyly is classified as a malformation, a failure of axis formation, and/or differentiation of the radioulnar hand plate, which leads to a process of bifurcation of digit(s) in the longitudinal axis that progresses from the distal to proximal end1,2,3  This bifurcation process occurs in numerous grades, resulting in a variety of deformities, ranging from a broadening of a distal phalanx to complete duplication of one or several fingers and carpal involvement3  Polydactyly can be inherited as an autosomal dominant or recessive mutation (eg, bilateral and symmetrical), or as a sporadic genetic mutation (eg, unilateral);2,13 the genes involved are related to the anterior-to-posterior axis of limb growth4

Related Anatomy

  • Upper limb digits are recognizable at 41-43 days after fertilization and are fully separate at 53 days; it is within this period of rapid development when the malformations of polydactyly become manifest1
  •  When the digits involved in the polydactyly deviate from their normal alignment they can encumber the thumb which is responsible for 40% of hand function and must be able to oppose the other digits to provide a stable pinch. 5
  • There are several dichotomous ways to classify polydactyly:
    • Preaxial (radial; bifurcation or duplication of the thumb) versus postaxial (ulnar; little finger); mixed polydactyly is the presence of both preaxial and postaxial polydactyly5
    • Central polydactyly is duplication of a non-border digit
    • Thumb versus triphalangeal
    • Simple versus complex
    • Wassel classification system, which is usually applied to thumb duplication, differentiates types of preaxial polydactyly
      • Type I: bifid distal phalanx
      • Type II: duplicated distal phalanx
      • Type III: bifid proximal phalanx
      • Type IV: duplicated proximal phalanx
        • The most common type of preaxial polydactyly
  • Type V: bifid metacarpal
  • Type VI: duplicated metacarpal
  • Type VII: Triphalangia5
  • The Temtamy and McKusick classification is most commonly used for diagnosing postaxial polydactyly
    • Type A: a well-developed digit that has an articulation with the 5th metacarpal
    • Type B: more common skin tag or a pedunculated soft tissue devoid of any bone, tendon, or nail
    • Bilateral duplication is most common, with unilateral presentation occurring most often in the left hand1
    • Although complete duplication of an entire digit can occur in central polydactyly, the deformity is often hidden within a syndactyly and referred to as synpolydactyly1

Incidence and Related Conditions

  • Polydactyly is the most common congenital limb anomaly noticed immediately at birth3
  • The prevalence of polydactyly is approximately 0.3–3.6/1,000 in live births and 1.6–10.7/1,000 in the general population, and it occurs in a male-to-female ratio of 2.5:16,7  Preaxial polydactyly is more common in Whites versus African Americans and also has a high incidence in American Indians and Asians; within these groups, thumb duplications represent up to 90% of all polydactyly cases12  Postaxial polydactyly is 10 times more common in African and African American populations compared to Whites, with a reported frequency of 1 in 143 live births in African Americans versus 1 in 1,339 live births in Whites13  Polydactyly more commonly occurs in isolation rather than with a syndrome, but it does manifest itself as an integral part or a common association with approximately 300 well-characterized syndromic malformations; the general rule is the more complex the polydactyly, the more likely that other anomalies are present3,5 
  • Other associated syndromes and congenital abnormalities include
    • Brachydactyly, syndactyly, short rib polydactyly
    • Blackfan-Diamond or Fanconi anemia
    • Chondroectodermal dysplasia
    • Cleft palate
    • Pollex abductus
    • Tibial defects
    • Triphalangeal thumb
    • Imperforate anus
    • Trisomy 13
    • Ulnar dimelia Syndromes like Acrocallosal, Bardet–Biedl, Basal cell nevus, Biemond, Down’s, Ellis-van Creveld, Holt-Oram, Jeune, Laurin-Sandrow, McKusic-Kauffman, Mohr, Oral-facial-digital, Pallister-Hall, Rubinstein-Taybi are also associated wuth polydactyly.
  • Preaxial polydactyly, the most commonly reported type of polydactyly, has an incidence of 0.08-1.4/1,000 live births8-11

Differential Diagnosis

  • Dermatologic manifestations of Down’s syndrome
  • Supernumerary digit with no bony attachment
  • Bifid thumbv
ICD-10 Codes

  • POLYDACTYLY

    Diagnostic Guide Name

    POLYDACTYLY

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    POLYDACTYLY, ACCESSORY FINGER(S)Q69.0   
    POLYDACTYLY, ACCESSORY THUMB(S)Q69.1   

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
Polydactyly Clinical Photos
  • Polydactyly left hand with extra fifth finger
    Polydactyly left hand with extra fifth finger
  • Polydactyly right hand with extra fifth finger
    Polydactyly right hand with extra fifth finger
  • Polydactyly left hand with extra fifth finger dorsal and palmar views
    Polydactyly left hand with extra fifth finger dorsal and palmar views
  • Skin deformity after a right fifth finger polydactyly with small skin and neurovascular bundle was removed by tying off the pedicle in the newborn nursery.
    Skin deformity after a right fifth finger polydactyly with small skin and neurovascular bundle was removed by tying off the pedicle in the newborn nursery.
  • Polydactyly of the hand can be associated with polydactyly of the toes.
    Polydactyly of the hand can be associated with polydactyly of the toes.
Symptoms
Bifurcated or duplicated digit(s)
Functional impairments of the finger and/or hand
Typical History

The typical patient is an 8-month-old boy. After he was born, his parents noticed the appearance of an additional fifth finger on his right hand due to a duplication of the distal metacarpal, proximal phalanx and distal phalanx. Following the advice of the pediatrician, the parents waited until the boy was at least 6 months old, and then presented to a hand surgeon to consider possible surgical options1,5

Positive Tests, Exams or Signs
Work-up Options
Images (X-Ray, MRI, etc.)
Polydactyly X-rays
  • Polydactyly X-ray left hand with extra fifth finger
    Polydactyly X-ray left hand with extra fifth finger
  • Polydactyly X-ray right hand with extra fifth finger
    Polydactyly X-ray right hand with extra fifth finger
  • Operative mini-fluoroscopy with K-wire performed to localize and document junction point of bifid metacarpal.
    Operative mini-fluoroscopy with K-wire performed to localize and document junction point of bifid metacarpal.
Treatment Options
Conservative
  • Some cases of polydactyly—especially type I preaxial and type A postaxial polydactyly—may not cause any major functional impairments; ongoing observation is a conservative treatment option but this choice is not accetable to most parents.
  • If the extra digit is not attached by any bones, a vascular clip may be used to remove it
Operative
  • Surgical intervention is often needed and is directed toward creating a functional and aesthetically satisfactory hand1
  • Preaxial polydactyly
    • Surgical decisions are primarily dependent on the extent of the bony duplication and soft tissue structures present, and the general principle is to remove the least functional component with reconstruction of the remaining parts
    • Thumb duplication usually requires ablation of the lesser digit, usually the radial thumb, with collateral ligament reconstruction to preserve dominantthumb.1  For thumb duplication also see the diagnostic guide for bifid thumb.
    • Types I and II
      • Typically treated with the Bilhaut-Cloquet procedure
        • Involves the removal of central tissue and combining both digits into one
        • Useful for both bifid and duplicated phalanges
    • Type III
      • Bifid proximal phalanx is narrowed by resection and realigned with osteotomy of the remaining diaphysis
    • Type IV
      • Advancement of the abductor pollicis brevis to the base of the proximal phalanx
        • Aids in metacarpophalangeal (MP) joint stabilization, abduction, and opposition
        • Metacarpal, occasionally with the proximal phalanx, may require realignment by closing wedge osteotomy
    • Types V and VI
      • Typically treated similarly to type IV, with addition of a first web space Z-plasty or web widening if there is thenar eminence contracture
      • Procedures usually require a more complex transfer of intrinsics and collateral ligaments
      • Rarely a segmental distal transfer (on-top plasty) may also be used when one digit has a superior proximal component and one digit has a superior distal fragment
      • Acral transposition has also been described, with transposition of the tip of the ablated digit in place of the tip of the kept digit
        • Ideal technique if one digit has a more normal proximal part while the other has a more normal distal part
    • Types VII
      • Typically treated similarly to type IV
      • A segmental distal transfer (on-top plasty) may also be used when one digit has a superior proximal component and one digit has a superior distal fragment
      • Resection of the delta phalanx or one interphalangeal (IP) joint is an alternative option5
  • Postaxial polydactyly
    • Type A
      • Treated similarly to preaxial polydactyly
      • Surgical excision of ulnar-most digit that preserves the radial digit and preserves or reconstructs the collateral ligaments from the ulnar digit remnant
      • Should be performed when the child is 6-12 months old1
    • Type B
      • Surgical excision
      • Suture ligation
        • Often performed immediately after birth in the nursery but when children present late then careful surgucal excision is indicated.
      • Ray amputation
        • Performed before 12 months
  • Medial polydactyly
    • Surgical intervention should be performed between 6-12 months of age
    • Osteotomy and ligament reconstruction
    • Ablation of the hypoplastic digit
    • Ray amputation is considered if surgery does not produce a stable, sensate radial pinch5
  • After surgery, physical and/or occupational therapy with appropriate splinting may be needed to improve hand and finger function
Treatment Photos and Diagrams
Surgical Treatment of Congenital Polydactyly
  • Right fifth finger polydactyly (insert). Fifth partial ray being being excised because of its incomplete metacarpal. Pin (arrow) in the metacarpal junction point.
    Right fifth finger polydactyly (insert). Fifth partial ray being being excised because of its incomplete metacarpal. Pin (arrow) in the metacarpal junction point.
  • Right fifth finger polydactyly with radial partial ray in forceps now excised. Insert shows potential appearance after repair or reconstruction of inter-metacarpal ligament.
    Right fifth finger polydactyly with radial partial ray in forceps now excised. Insert shows potential appearance after repair or reconstruction of inter-metacarpal ligament.
  • Right fifth finger polydactyly most correction at suture removal. Mild swelling still present.
    Right fifth finger polydactyly most correction at suture removal. Mild swelling still present.
  • Left fifth finger polydactyly with incision plan
    Left fifth finger polydactyly with incision plan
  • Left fifth finger polydactyly with dorsal incision opened, extensor retracted (1) and bifid portion of the metacarpal head visible (2).
    Left fifth finger polydactyly with dorsal incision opened, extensor retracted (1) and bifid portion of the metacarpal head visible (2).
  • Left fifth finger polydactyly after volar approached used to identify and cut the digital arteries, digital nerves and flexor tendons. Extra digit now removed. Extensor to be attached to intact fifth extensor seen (1) and collateral (2) will be saved and used in reconstruction after partial metacarpal head remove by an osteotomy.
    Left fifth finger polydactyly after volar approached used to identify and cut the digital arteries, digital nerves and flexor tendons. Extra digit now removed. Extensor to be attached to intact fifth extensor seen (1) and collateral (2) will be saved and used in reconstruction after partial metacarpal head remove by an osteotomy.
  • Left fifth finger polydactyly closure after excise of extra partial ray and reconstruction.
    Left fifth finger polydactyly closure after excise of extra partial ray and reconstruction.
  • Left fifth finger polydactyly. Note extensor tendon (arrow).
    Left fifth finger polydactyly. Note extensor tendon (arrow).
  • Left fifth finger polydactyly. Note extensor tendon (1), collateral ligament (2), and excised digit (3).
    Left fifth finger polydactyly. Note extensor tendon (1), collateral ligament (2), and excised digit (3).
  • Left fifth finger polydactyly. Note collateral ligament (1) and K-wire (2) used to localize the osteotomy line.
    Left fifth finger polydactyly. Note collateral ligament (1) and K-wire (2) used to localize the osteotomy line.
  • Left fifth finger polydactyly. Note excised metacarpal head (1), collateral ligament (2) and K-wire used to localize the osteotomy line.
    Left fifth finger polydactyly. Note excised metacarpal head (1), collateral ligament (2) and K-wire used to localize the osteotomy line.
  • Right foot after excision of extra fifth toe
    Right foot after excision of extra fifth toe
CPT Codes for Treatment Options

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Complications
  • Diminished digit size
  • Residual bump
  • Zigzag deformity
  • Hypertrophic scar
  • Joint stiffness, enlargement and/or instability
  • Abnormal physeal growth
  • Nail deformity and/or ridges
  • Infection
  • Neuroma
  • Discoloration
  • Reoperation
Outcomes
  • Duplicated digits that requires surgical correction will never be completely normal, but it is possible to achieve acceptable function5
    • Surgically corrected thumb duplications usually turn out stiffer, shorter, and thinner than their normal counterparts
    • Some amount of contracture and abnormal function is sometimes seen in the index-, long-, and ring-finger duplications5
  • Cosmetic results with the Bilhaut-Cloquet procedure are unpredictable because of surgical damage to the nail's germinal matrix.  However, surgical results today have been improved with microtechniques and the preservation of entire nails5
  • Suture ligations of tiny duplicate fifth digits rarely lead to a perfectly normal cosmetic appearance and residual bumps are fairly common2
  • Parents should be warned that secondary surgeries to correct angulation deformities and/or joint instability are often needed as these children grow.
Key Educational Points
  • Polydactyly is considered a complex problem and unique challenge for hand surgeons; careful consideration and planning of surgical treatment individualized to each patient is therefore required to obtain the best possible outcome2
  • Patients’ family members should always be counseled that more surgery may be needed in the future, as further deformity can occur with growth5
  • Polydactyly can also be detected by ultrasound as early as 14 weeks’ gestation, with partial autoamputation seen in most isolated polydactylies
  • Surgical intervention is typically recommended between 6-12 months of age, before fine motor skills have completely developed; the risk of anesthesia is greater at an earlier age and the structures that most be manipulated surgically are tiny.
  • Blood tests may be needed to help identify any other syndromes that may be present.
  • Any patient with syndromic findings or atypical presentations (see above) should be referred to a geneticist5
References

Cited

  1. Guo B, Lee SK, Paksima N. Polydactyly: a review. Bull Hosp Jt Dis (2013) 2013;71(1):17-23. PMID: 24032579
  2. Singer G, Thein S, Kraus T, et al. Ulnar polydactyly - an analysis of appearance and postoperative outcome. J Pediatr Surg 2014;49(3):474-6. PMID: 24650481
  3. Malik S. Polydactyly: phenotypes, genetics and classification. Clin Genet 2014;85(3):203-12. PMID: 24020795
  4. Verma PK, El-Harouni AA. Review of literature: genes related to postaxial polydactyly. Front Pediatr 2015;3:8. PMID: 25717468
  5. Faust KC, Kimbrough T, Oakes JE, et al. Polydactyly of the hand. Am J Orthop (Belle Mead NJ) 2015;44(5):E127-34. PMID: 25950541
  6. Mellin GW. The frequency of birth defects. Birth defects. Philadelphia, PA: Lippincott JB, 1963;1–17.
  7. Castilla E, Paz JE, Mutchinick O, et al. Polydactyly-a genetic study in South America. Am J Hum Genet 1973;25:405–412. PMID: 4716659
  8. Baek GH. Duplication. In: Abzug JM, Kozin SH, Zlotolow DA, eds. The Pediatric Upper Extremity. New York, NY: Springer- Verlag; 2015:325–368.
  9. Goldfarb CA, Wall LB, Bohn DC, et al. Epidemiology of congenital upper limb anomalies in a midwest United States population: an assessment using the Oberg, Manske, and Tonkin classification. J Hand Surg Am 2015;40:127–132. PMID: 25534840
  10. Sesgin MZ, Stark RB. The incidence of congenital defects. Plast Reconstr Surg Transplant Bull. 1961;27:261–267.
  11. Temtamy SA, McKusick VA. The genetics of hand malformations. Birth Defects Orig Artic Ser. 1978;14:i–xviii, 1–619.
  12. Leung PC, Chan KM, Cheng JC. Congenital anomalies of the upper limb among the Chinese population in Hong Kong. J Hand Surg Am 1982;7(6):563-5. PMID: 6294174
  13. Watson BT, Hennrikus WL. Postaxial type-B polydactyly. Prevalence and treatment. J Bone Joint Surg Am 1997;79(1):65-8. PMID: 9010187

New Articles

  1. Singer G, Thein S, Kraus T, et al. Ulnar polydactyly - an analysis of appearance and postoperative outcome. J Pediatr Surg 2014;49(3):474-6. PMID: 24650481
  2. Malik S. Polydactyly: phenotypes, genetics and classification. Clin Genet 2014;85(3):203-12. PMID: 24020795
  3. Verma PK, El-Harouni AA. Review of literature: genes related to postaxial polydactyly. Front Pediatr 2015;3:8. PMID: 25717468
  4. Manske MC, Kennedy CD, Huang JI. Classifications in Brief: The Wassel Classification for Radial Polydactyly. Clin Orthop Relat Res 2017;475(6):1740-1746. PMID: 27613532

Reviews

  1. Guo B, Lee SK, Paksima N. Polydactyly: a review. Bull Hosp Jt Dis (2013) 2013;71(1):17-23. PMID: 24032579
  2. Verma PK, El-Harouni AA. Review of literature: genes related to postaxial polydactyly. Front Pediatr 2015;3:8. PMID: 25717468
  3. Faust KC, Kimbrough T, Oakes JE, et al. Polydactyly of the hand. Am J Orthop (Belle Mead NJ) 2015;44(5):E127-34. PMID: 25950541

Classics

  1. Hare PJ. Rudimentary polydactyly. Br J Dermatol 1954;66(11):402-8. PMID: 13208927
  2. Karchinov K. The treatment of polydactyly of the hand. Br J Plast Surg 1962;15:362-76. PMID: 13962469
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