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BIFID THUMB (DUPLICATE THUMB, SUPERNUMERARY THUMB)

Introduction

Thumb polydactyly is a type of radial or preaxial polydactyly because it affects the radial side of the hand. The clinical features associated with thumb polydactyly will depend on the extent of the duplication and can range from a barely visible broadening of the distal phalanx to the presence of a complete, supernumerary digit. The Wassel classification1 is the most widely used for radial polydactyly. The modern Wassel classication is shown in the diagram below. For all of the possible osseous malformations associated with thumb polydactyly, there are as many additional deformities to tendons, ligaments, other types of connective tissue and skin. In light of this, there appears to be worldwide consensus among both patients and practitioners that the best approach to management – for both aesthetics and function – is to reduce the condition to the best possible thumb. This usually means resecting the radial thumb which is often the more hypoplastic one.    It should be noted that neither thumb has a complete set of normal full size components.8 

Incidence and Inheritance

  • 1 per 1000 to 10,000 live birth; more prevalent in boys than in girls.
     
  • Wassel Type IV is most common, followed by Type II.
  • More common in Whites than African Americans
  • Also seen in Native Americans and Asian populations 8

Associated Conditions and Syndromes

  • Blackfan-Diamond anemia
  • Cleft palate
  • Fanconi’s anemia
  • Holt-Oram syndrome
  • Imperforate anus
  • Tibial defects
ICD-10 Codes

  • BIFID THUMB (DUPLICATE THUMB, SUPERNUMERARY THUMB)

    Diagnostic Guide Name

    BIFID THUMB (DUPLICATE THUMB, SUPERNUMERARY THUMB)

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

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    BIFID THUMB (DUPLICATE THUMB, SUPERNUMERARY THUMB)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
  • Bifid Thumb Right Dorsal (Wassel II)
    Bifid Thumb Right Dorsal (Wassel II)
  • Bifid Thumb Right Palm (Wassel II)
    Bifid Thumb Right Palm (Wassel II)
  • Bifid Thumb Right (Wassel IV) dorsal view with small radial thumb
    Bifid Thumb Right (Wassel IV) dorsal view with small radial thumb
  • Bifid Thumb Left (Wassel IV) dorsal view
    Bifid Thumb Left (Wassel IV) dorsal view
  • Bifid Thumb Right (Wassel IV) palmar view with small radial thumb
    Bifid Thumb Right (Wassel IV) palmar view with small radial thumb
  • Bifid Thumb right (Wassel V) dorsal view
    Bifid Thumb right (Wassel V) dorsal view
Basic Science Photos and Related Diagrams
Basic Science Pics
  • Wassel's Duplicate (Bifid) Thumb Classification modified from Wassel (ref-1)
    Wassel's Duplicate (Bifid) Thumb Classification modified from Wassel (ref-1)
Symptoms
Deformed duplicated thumb
Positive Tests, Exams or Signs
Work-up Options
Images (X-Ray, MRI, etc.)
  • Bifid Thumb Right ( Wassel IV). Note wide metacarpal head (arrow).
    Bifid Thumb Right ( Wassel IV). Note wide metacarpal head (arrow).
  • Bifid Thumb Right ( Wassel V). Note bifid first metacarpal (arrow).
    Bifid Thumb Right ( Wassel V). Note bifid first metacarpal (arrow).
  • Bifid Thumb Right ( Wassel VI)
    Bifid Thumb Right ( Wassel VI)
  • Bifid Thumb Right ( Wassel II) post AP with shaved metacarpal head (arrow)
    Bifid Thumb Right ( Wassel II) post AP with shaved metacarpal head (arrow)
Treatment Options
Conservative
  • None
Operative
  • Excision: Excision of one small hypoplastic is rare but appropriate when:
    1. the duplicate is a small excrescence and attached to or protruding from the major normal appearing thumb
    2. a hypoplastic accessory thumb is widely separated from a near-normal thumb.
  • Combination of Parts from both Thumbs:
    • Bilhaut-Cloquet procedure: equivalent portions of the digits are removed, and they are brought together along the midline. This procedure is in frequently used becuase of the risks of nail deformity, growth plate damage and IP jjooint stiffness. A modified procedure described by Baek et al may be useful it minimizes the risk of nail and epiphyseal plate damge.9
    • Asymmetric or nearly symmetric: one digit is retained (usually ulnar thumb) and augmented by portions of the deleted radial thumb
  • Surgical reconstruction steps for Wassel IV Bifid (Duplicate) Thumb - Also see: Treatment Photos and Diagrams
    1. Design the skin incision to provide coverage for the defect that will be created by amputating the radial thumb.  This coverage can be facilitated by using a dorsal flap from the amputated radial thumb.  The skin incision should also be designed so that final closure will be a curvilinear incision that will not cause  skin contractures and subsequent thumb deformity.
    2. Open the incision and raise the dorsal radial flap to expose the extensor tendons and dorsal capsule of the radial thumb’s MP joint and the PIP joint.
    3. Release the radial thumb extensor pollicis longus (EPL) at or near its insertion into the distal phalanx of the radial thumb.
    4. Open the radial thumb MP joint dorsal capsule to expose the radial collateral ligament. Note the lack of collateral ligaments between the two proximal phalanges.
    5. Release the radial collateral ligament of the radial thumb from the proximal phalanx by raising the collateral off the proximal phalanx with a periosteal sleeve.
    6. Turn the hand over and exposed the radial thumb’s neurovascular bundle and FPL through the volar incision.
    7. Cauterize the radial thumb’s radial digital artery and transect the radial digital nerve.  Allow the digital nerve stump to recess into the stump’s soft tissues.  Do the same for the radial thumb ulnar digital artery and nerve; however, be careful to transect the ulnar digital nerve and artery distal to the bifurcation of the common digital nerve and artery in order to avoid damaging the radial digital nerve and artery to the retained ulnar thumb.
    8. Identified the radial thumbs flexor pollicis longus (FPL) and mobilize it before transecting it distal to the radial thumbs MP joint. Save this FPL to reinforce the ulnar thumbs flexor pollicis longus.
    9. Next exposed the radial thumb’s volar plate. Release the volar plate at its insertion into the base of the proximal phalanx.
    10. Now remove the radial thumb’s distal portions ( thumb tip, thumbnail, distal phalanx and proximal phalanx of the radial thumb).
    11. Begin the ulnar thumb reconstruction by trimming the radial half of the metacarpal head.  In young children this can usually be done with an appropriate sized scalpel. Carefully preserved the attachments of the radial thumb’s radial collateral ligament to the neck of the thumb metacarpal by retaining the connection between the collateral ligament and the periosteum.
    12. Place an appropriate size K wire retrograde through the ulnar thumb’s proximal and distal phalanges.  Then aligned metacarpal joint of the ulnar thumb and drive the K wire into the metacarpal head and shaft.
    13. Once the metacarpal head is narrowed and pinned, reattach the radial collateral ligament and any preserve thenar muscle insertions into the base of the ulnar thumb’s proximal phalanx. Occasionally, the retained metacarpal or phalanges may have angular deformities that require realignment by adding closing wedge osteotomies.
    14. Use the preserved radial thumb extensor pollicis longus (EPL) and flexor pollicis longus (FPL) if necessary to reinforce the ulnar thumb’s extensor and flexor tendons.  The alignment of these tendons can also be used to help balance the ulnar thumbs MP joint and IP joints.
    15. Irrigate the incisional areas, deflate the tourniquet and check for any excessive bleeding.  If necessary, reinflate the tourniquet and proceed with skin closure.
    16. The first step of closure will be to fit the dorsal skin flap into the defect created by removing the radial thumb.  This flap may be trimmed as necessary to fit the defect. Closed the incisions with the absorbable sutures.  Occasionally it is appropriate use nonabsorbable nylon sutures at areas of increased tension.
    17. Finally apply a soft dressing and a long arm thumb spica cast.
  • Revision: second surgeries for static/dynamic imbalance, instability, nail deformity and growth related deformities.
  • Surgical recommendations by Wassel Type include:
  • 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
Treatment Photos and Diagrams
  • Bifid Thumb (Wassel 2) with dorsal incisions outlined. The large dorsal flap on the radial thumb will eventually fold into the defect created by removal of the radial thumb.
    Bifid Thumb (Wassel 2) with dorsal incisions outlined. The large dorsal flap on the radial thumb will eventually fold into the defect created by removal of the radial thumb.
  • Bifid Thumb (Wassel 2) with palmar (I&II) incisions outlined. The larger palmar flap II on the radial thumb can fold dorsally and distally into the defect created by removal of the radial thumb. Alternatively palmar I can be used and the defect filled completely by the dorsal flap.
    Bifid Thumb (Wassel 2) with palmar (I&II) incisions outlined. The larger palmar flap II on the radial thumb can fold dorsally and distally into the defect created by removal of the radial thumb. Alternatively palmar I can be used and the defect filled completely by the dorsal flap.
  • Bifid Thumb (Wassel 2) with dorsal incisions opened. Radial EPL in clamp at arrow. This will reinforced the ulnar EPL.
    Bifid Thumb (Wassel 2) with dorsal incisions opened. Radial EPL in clamp at arrow. This will reinforced the ulnar EPL.
  • Bifid Thumb (Wassel 2) with dorsal incisions opened. Radial collateral and periosteum have been dissected off the radial distal phalanx (arrow). These tissues will be attached to the radial aspect of the ulnar thumb (double arrows).
    Bifid Thumb (Wassel 2) with dorsal incisions opened. Radial collateral and periosteum have been dissected off the radial distal phalanx (arrow). These tissues will be attached to the radial aspect of the ulnar thumb (double arrows).
  • Bifid Thumb (Wassel 2) with dorsal incisions opened. Noted there are no collateral ligaments eat the junction of the two portions of the bifid thumb.
    Bifid Thumb (Wassel 2) with dorsal incisions opened. Noted there are no collateral ligaments eat the junction of the two portions of the bifid thumb.
  • Bifid Thumb (Wassel 2) with dorsal incisions opened. The wide proximal phalanx head will be narrowed radially by cutting away cartilage without detaching the collateral ligament origin.
    Bifid Thumb (Wassel 2) with dorsal incisions opened. The wide proximal phalanx head will be narrowed radially by cutting away cartilage without detaching the collateral ligament origin.
  • Bifid Thumb (Wassel 2) with the final curved incision. Note the use of the palmar and dorsal flaps from the amputated radial thumb.
    Bifid Thumb (Wassel 2) with the final curved incision. Note the use of the palmar and dorsal flaps from the amputated radial thumb.
  • Bifid Thumb Right (Wassel IV) dorsal with radial thumb amputation defect (1) filled by large dorsal flap (2).
    Bifid Thumb Right (Wassel IV) dorsal with radial thumb amputation defect (1) filled by large dorsal flap (2).
  • Bifid Thumb Right ( Wassel IV) palmar view. Note split FPL (1) and FPL to ulnar thumb which will be reinforced by transfer of the radial FPL to insertion (2). Note preserved radial neurovascular bundle (3) and skin hook (4) stabilizing radial thumb.
    Bifid Thumb Right ( Wassel IV) palmar view. Note split FPL (1) and FPL to ulnar thumb which will be reinforced by transfer of the radial FPL to insertion (2). Note preserved radial neurovascular bundle (3) and skin hook (4) stabilizing radial thumb.
  • Bifid Thumb Right with preserved EPL and radial collateral to use in ulnar thumb reconstruction.
    Bifid Thumb Right with preserved EPL and radial collateral to use in ulnar thumb reconstruction.
  • Bifid Thumb Right ( Wassel IV) dorsal view with K-wire stabilizing reconstructed collateral ligament. Note original radial EPL insertion site (2) and skeletanized proximal phalanx (3) because must radial tissue used to reconstruct the ulnar thumb.
    Bifid Thumb Right ( Wassel IV) dorsal view with K-wire stabilizing reconstructed collateral ligament. Note original radial EPL insertion site (2) and skeletanized proximal phalanx (3) because must radial tissue used to reconstruct the ulnar thumb.
CPT Codes for Treatment Options

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Common Procedure Name
Supernumerary digit excision and reconstruction
CPT Description
Reconstruction of supernumerary digit soft tissue and bone
CPT Code Number
26587
CPT Code References

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CPT 2021 Professional Edition: Spiralbound

Complications
  • Reconstructed thumb almost always smaller than the normal thumb 10
  • Neurovascular trauma, paresthesias 
  • Postoperative deformities, inadequate or abnormal motor tendon units 
  • Joint instability, abnormal physis growth, bony malalignment and length discrepancy
  • Angulation of the IP joint very common after Wassel IV reconstruction 7
  • Limited range of motion
  • Scar contracture
  • Z-deformity of the thumb
Outcomes
  • 88% satisfied/very satisfied with cosmetic and functional outcome.2
  • Excellent functional and good aesthetic results.3
  • Long-term results are excellent; however, revision rates trend upward with time (20-25%).4,7
Key Educational Points
  • Parents should be told to expect a smaller than normal reconstructed thumb
  • Parents should be told to expect reversion surgeries as the child grows
  • Joint instabilities often require chondrodesis or athrodesis rather than ligament reconstruction
References
  1. Wassel HD. The results of surgery for polydactyly of the thumb. A review. Clin Orthop Relat Res 1969;64:175-93. PMID: 4894526
  2. Yen CH, et al. Thumb polydactyly: clinical outcome after reconstruction. J Orthop Surg (Hong Kong) 2006;14(3):295-302. PMID: 17200532
  3. Kemnitz S, De SL. Pre-axial polydactyly: outcome of the surgical treatment. J Pediatr Orthop B 2002;11(1):79-84. PMID: 11866087
  4. Stutz C, et al. Long-term outcomes following radial polydactyly reconstruction. J Hand Surg Am 2014;39(8):1549-52. PMID: 24996673
  5. Hasegawa K, Namba Y, Kimata Y. Thumb polydactyly with a floating ulnar thumb. Acta Med Okayama 2013;67(6):391-5. PMID: 24356724
  6. Iba K, et al. Arthrography in thumb polydactyly with bifurcation at the interphalangeal or metacarpophalangeal joints provides practical information at surgery. J Hand Surg Eur 2013;38(3):267-71. PMID: 22733700
  7. Goldfarb CA, Patterson JM, Maender A, Manske PR. Thumb size and appearance following reconstruction of radial polydactyly. J Hand Surg Am. 2008;33:1348-1353. PMID: 18929199 
  8. Ezaki M.  Radial polydactyly. Hand Clin 1990; 6: 577-588. PMID: 2269673
  9. Baek GH, Gong HS, Chung MS et al. Modified Bilhaut-Cloquet procedure for Wassel type II and III polydactyly of the thumb. J Bone Joint Surg Am 2007; 89:534-541. PMID: 17332102
  10. Mih ASD.  Complications of duplicate thumb reconstruction. Hand Clin 1998; 14: 143-149. PMID: 9526163
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