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HYPOPLASTIC THUMB & POUCE FLOTTANT

Introduction

Thumb hypoplasia is a rare congenital disorder in which the thumb is underdeveloped or completely absent. The condition is bilateral in ~60% of patients, and the male:female ratio is 1:1. Because most hand functions require the thumb, surgery to reconstruct a serviceable thumb is the usual treatment. For the same reason, even moderate outcomes have significantly positive effects on quality of life. The timing of surgery is controversial. Currently, it is usually performed at ~1 year of age. In addition to the functional deficits of thumb hypoplasia, the psychological impact on the child should be considered. Successful surgical outcomes can mitigate this impact.

Related Anatomy

  • Absence or weakness of intrinsic muscles
  • Extrinsic muscle weakness (less common)
  • Interphalangeal flexion insufficiency due to anomalies within the flexor pollicis longus
  • Narrowing of the first web space
  • Ulnar metacarpophalangeal (MP) joint instability due to collateral ligament laxity
  • Underdeveloped or absent extensor pollicis brevis tendon

Incidence and Related Conditions

  • Extremely rare (1 in 100,000 infants)
  • Thumb underdevelopment accompanies many congenital conditions, including:
    • Apert’s syndrome
    • Brachydactyly
    • Cleft hand complex
    • Congenital constriction ring syndrome
    • Rubinstein–Taybi syndrome
    • Symbrachydactyly
    • Thumb duplication (pre-axial polydactyly)
    • Transverse deficiencies
    • Ulnar longitudinal deficiency

Differential Diagnosis

  • Faconi anemia
  • Holt-Oram syndrome
  • Radial deficiency
  • Tar syndrome
  • VACTERL: Vvertebral abnormalities, Anal atresia, Cardiac abnormalities, Tracheo-esophageal fistula and/or Esophageal atresia, Renal agenesis and dysplasia, and Limb defects  
  • VATER syndrome: birth defects possible in the Vertebrae, Anus, Trachea, Esophagus, or Renal (kidneys) 

Exam Findings, Signs and Positive Tests

  • The patient may be unable to actively flex or oppose the thumb.
  • The Blauth classification of thumb hypoplasia
    • Grade 1: thumb small, but joints stable; minor hypoplasia; no treatment
    • Grade 2: all joints present, but MP is unstable; thenar hypoplasia; first web underdeveloped; tendon anomalies
    • Grade 3: proximal metacarpal absent and severe hypoplasia
      • 3A: Carpometalcarpal (CMC) joint is intact
      • 3B: CMC joint is deficient or absent
  • Grade 4: entire metacarpal absent; skin bridge with neurovascular bundle attaches thumb elements to hand; also called “floating” thumb (Pouce Flottant).
  • Grade 5: thumb absent
ICD-10 Codes

  • HYPOPLASTIC THUMB

    Diagnostic Guide Name

    HYPOPLASTIC THUMB

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

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    HYPOPLASTIC THUMBQ68.1   

    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
Hypoplastic Thumbs
  • Right Hypoplastic Thumb Type 3B
    Right Hypoplastic Thumb Type 3B
  • Pouce Flottant (Floating Left Thumb) - Hypoplastic Thumb Type 4
    Pouce Flottant (Floating Left Thumb) - Hypoplastic Thumb Type 4
  • Right Hypoplastic Thumb Type 4 (dorsal and palmar views)
    Right Hypoplastic Thumb Type 4 (dorsal and palmar views)
  • Right Hypoplastic Thumb Type 5
    Right Hypoplastic Thumb Type 5
  • Hypoplastic hand with relatively normal thumb
    Hypoplastic hand with relatively normal thumb
Pathoanatomy Photos and Related Diagrams
Incisions for Pollicization
  • Carroll's dorsal and palmar incisions for pollicization of the index finger.
    Carroll's dorsal and palmar incisions for pollicization of the index finger.
Symptoms
Thumb(s) smaller in size, or absent with difficulty or inability to grasp and pinch
Thumb MP joint instability
Index finger pronation with middle-index web space deep and wide
Typical History

The patient may be male or female. If the patient has reached developmental stages beyond 1 year (the typical age of surgical treatment), parents are likely to describe reduced mobility and function (eg, precision, grip, span, and strength) of the child’s thumb. Activities of daily living will have been negatively affected. There may or may not be a family history of the disorder. 

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Conservative

Thumb hypoplasia Grade 1 can be treated without surgery. 

Operative

Thumb hypoplasia beyond Grade 1 is treated surgically.

  • If the CMC joint is intact (Grades 2-3A), rebuild ligaments and tendons:
    • Stabilize MP joint
    • Release of first web space
    • Opponensplasty ( Huber type opponensplasty maybe useful in these patients)
  • If the CMC joint is deficient or absent (Grades 3B-4),* or the thumb is completely absent (Grade 5), pollicization is performed:
    • Amputation of the non-functional, unstable digit
    • Movement of the index finger to the thumb position
  • In all cases, post-surgical hand therapy is required for full mobility of the hand
  • Subsequent operations may be necessary to deepen the web space (eg, four-flap webplasty) or improve motion

* Note: reconstruction of Grade 3 and 4 thumbs is sometimes possible. However, results are inferior to those obtained from a well-performed pollicization. 

Pollicization surgical steps include:

  1. The incisions for pollicization are designed to allow excision of a hypoplastic thumb (if present), exposure of the neurovascular bundles, interosseous muscles and the bones of the index ray.  Finally, the incisions must provide a palm based skin flap which can be used to reconstruct a new first web between the pollicized index finger and the retained long finger ray.  (See figure in surgical images section).
  2. The first dorsal interosseous and the first volar interosseous muscles are detached distally from the index ray and later there distal tendons are sutured back into the base of the proximal phalanx of the pollicized index finger.  These muscles become the new abductor and abductor muscles of the reconstructed thumb.
  3. Ligation of the radial digital artery to the long finger and preserving the ulnar neurovascular bundle to the index finger is an important step in pollicization.  The common digital nerve in the index long web must be split in the internal epineurial plane at its bifurcation in order to provide two separate digital nerves, one to the ulnar aspect of the index finger and one to the radial aspect of the long finger with a new bifurcation at the level of the carpal tunnel.
  4. Through the dorsal incision the index metacarpal shaft is partially resected preserving the head of the index metacarpal and the base of the index metacarpal.  The index finger and the metacarpal head are rotated 120 degrees during the pollicization.  The new thumb is positioned in 45 degrees of abduction and 45 degrees of extension from the plane of the palm.  The preserved portions of the index metacarpal ultimately become the new trapezium.
  5. The distal metacarpal is preserved and rongeured proximal to the epiphyseal plate to make a point that can be placed into the hollowed out retained base of the index metacarpal.  This complex metacarpal osteoplasty is stabilized with a pin through the proximal phalanx, the distal portion of the metacarpal, the preserved proximal portion of the metacarpal and the carpal bones.  Ultimately. This metacarpal osteoplasty produces a new trapezium as a base for the pollicized index finger thumb.
  6. The web is finally reconstructing using the palmar based flap design while making the initial incisions for the pollicization.
  7. The new thumb is immobilized until the pin is remove around 3-4 weeks post-operatively.  After cast removal hand therapy and nighttime splinting is carried out for 2-4 months.
Treatment Photos and Diagrams
Surgical treatment of Hypoplastic Thumb
  • Left Hypoplastic Thumb Type 4 [ Flottant (Floating Left Thumb) ]
    Left Hypoplastic Thumb Type 4 [ Flottant (Floating Left Thumb) ]
  • Left Hypoplastic Thumb Type 4 Pollicization: Neurovascular bundles (1); Flexor tendons index (2); Palmar flap for web reconstruction (3)
    Left Hypoplastic Thumb Type 4 Pollicization: Neurovascular bundles (1); Flexor tendons index (2); Palmar flap for web reconstruction (3)
  • Left Hypoplastic Thumb Type 4 Pollicization: Carroll style incisions opened with exposed extensor tendons (1); web flap before elevation on palmar base (2); amputated pouce flottant (3).
    Left Hypoplastic Thumb Type 4 Pollicization: Carroll style incisions opened with exposed extensor tendons (1); web flap before elevation on palmar base (2); amputated pouce flottant (3).
  • Left Hypoplastic Thumb Type 4 Pollicization with thumb held in new position with a K-wire and web flap retracted.
    Left Hypoplastic Thumb Type 4 Pollicization with thumb held in new position with a K-wire and web flap retracted.
  • Left Hypoplastic Thumb Type 5 for pollicization
    Left Hypoplastic Thumb Type 5 for pollicization
  • Left Hypoplastic Thumb Type 5 pollicization skin incisions (palmar flap not used)
    Left Hypoplastic Thumb Type 5 pollicization skin incisions (palmar flap not used)
  • Left Hypoplastic Thumb Type 5 pollicization complete
    Left Hypoplastic Thumb Type 5 pollicization complete
  • Right Hypoplastic Thumb Type 3A after reconstruction. Note limited functional value (insert).
    Right Hypoplastic Thumb Type 3A after reconstruction. Note limited functional value (insert).
CPT Codes for Treatment Options

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Common Procedure Name
Pollicization of digit
CPT Description
Pollicization of a digit
CPT Code Number
26550
CPT Code References

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Complications
  • Conflict between stability and  mobility of the thumb
  • Pollicization is technically demanding, with high incidence of complications
  • Limited extension
  • Marginal skin necrosis
  • Poor opposition
  • Scar contracture
  • Venous congestion
  • Postoperative adhesions (rare)
Outcomes
  • Pollicization:
    • Tthumb not as strong or as mobile as a normal thumb
    • Functionality of the hand greatly improved
    • Newly possible skills (eg, handwriting, playing sports)
    • Optimal thumb function and satisfactory appearance
    • Quality of life greatly improved
  • Thumb reconstruction: results uniformly good 
Key Educational Points
  • Thumb hypoplasia may occur as an isolated condition, or along with radial hypoplasia.
  • The timing of surgery is chosen to according to the child’s transition from ulnar-sided to radial-sided prehension.
  • A triad of factors requires special consideration during surgical planning: narrowing of the first web space, lack of opposition, and ulnar MP joint instability. 
  • Evaluation of the thenar muscle and opposition function in very young children can be difficult due to poor infant/child cooperation and small hand size. 
  • Work-Up options for patients with hypoplastic thumbs include cardiac echocardiogram, complete blood cell count, genetic testing and counciling, hand ultrasound, after 6 years of age when thumb hypoplasia indeterminate, renal ultrasound and hand X-rays.
  • Pollicization is the treatment of choice for hypoplastic thumbs Type IIIB, Type 4 and Type 5.  Successful hypoplastic thumb reconstruction requires a stable thumb CMC joint.  If the thumb CMC joint is deficient or absent, then pollicization of the index finger is indicated.
  • Pollicization will require mobilizing the neurovascular bundle to the index finger and the index /long finger web.  The radial digital artery to the long finger will have to be ligated. The common digital nerve in  index/long finger interval will have to be split in the internal epineurium tissue plane to create a separate ulnar digital nerve to the index finger.  Next shortening and rotating the metacarpal will be performed to create a new trapezium.  Finally, a new first web will be constructed using the palmar based skin flap.
  • When treating hypoplastic thumbs distraction osteogenesis is not indicated because of unstable joints, web contractures and thenar muscle hypoplasia.2,3
  • The possible relationships of hypoplastic thumb to other congenital syndromes must be considered and appropriate imaging, cardiac evaluation and laboratory workup performed.3
References

New Articles

  1. Vuillermin C, Butler L, Lake A, et al. Flexor digitorum superficialis opposition transfer for augmenting function in types II and IIIa thumb hypoplasia. J Hand Surg Am 2016;41(2):244-9. PMID: 26718076
  2. Wall LB, Goldfarb CA. Tendon transfers for the hypoplastic thumb. Hand Clin 2016;32(3):417-21. PMID: 27387085

Reviews

  1. Dautel G. Management strategy for congenital thumb differences in paediatric patients. Orthop Traumatol Surg Res 2017;103(1S):S125-33. PMID: 27940039
  2. Kozin SH, Zlotolow DA. Common pediatric congenital conditions of the hand. Plast Reconstr Surg 2015;136(2):241e-257e. PMID: 26218399
  3. Soldado F, Zlotolow DA, Kozin SH, Thumb hypoplasia. J Hand Surg AM 2013; 38(7): 1435-1444.

Classics

  1. Matthews D. Congenital absence of functioning thumb. Plast Reconstr Surg Transplant Bull 1960;26:487-93. PMID: 13768282
  2. Bowe JJ. Transposition of the index finger for congenital absence of the thumb and thenar eminence. Plast Reconstr Surg (1946) 1954;13(6):475-80. PMID: 13177187
  3. Manske PR, McCarroll HR Jr, James MA. Type IIIA hypoplastic thumb. J Hand Surg AM 1995; 20: 246-253.
  4. Buck-Gramoko D. Pollicization of the index finger: method and results in aplasia and hypoplasia of the thumb. J Bone J Surg AM 1971; 53:1605-1617.
  5. Carroll RE. Pollicizatiion. In Operative Hand Sugerry 2nd edition. Green DP (ed). Churchill Livingstone, New York. 1988, pp 2263-2279.
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