DEFINITION

Polydactyly refers to having greater than the normal number of digits. Preaxial polydactyly is duplication or splitting of the thumb.

Central polydactyly is duplication of the central digits (index, middle, and ring). Postaxial polydactyly is duplication of the small finger.

ANATOMY

In cases of digit duplication, one may observe duplication in some or all of the elements of the finger (bone, nail, joints, and tendon). The duplicate finger may be well formed and near normal in appearance or underdeveloped and rudimentary in appearance.

Wassel published a classification of thumb duplication based on the work of Adrian Flatt, MD (Table 1). Postaxial polydactyly classification

Type A: well-formed duplicate small finger with bone or tendon attachments (FIG 1) Type B: small pediculated nubbin

PATHOGENESIS

Duplication of the digits occurs early in embryogenesis.

Patterning of the limb is demonstrated in three axis: proximodistal axis (modulated by the apical ectodermal ridge [AER]), anteroposterior axis (modulated by the zone of polarizing activity [ZPA]), and the dorsoventral axis regulated by the Engrailed 1 protein (EN1).

Abnormal or ectopic presence of sonic hedgehog protein is implicated in preaxial polydactyly. Familial cases of postaxial polydactyly demonstrate a defect in the GLI3 gene.

Table 1 Wassel Classification of Thumb Duplication

Type

Description

I

Bifid distal phalanx

II

Duplicate distal phalanx

III

Bifid proximal phalanx

IV

Duplicate proximal phalanx

V

Bifid metacarpal

VI

Duplicate metacarpal

VII

Triphalangeal thumb

From Wassel HD. The results of surgery for polydactyly of the thumb. Clin Orthop Relat Res

1969;64:175-193.

PATIENT HISTORY AND PHYSICAL FINDINGS

The diagnosis of polydactyly is straightforward, clinical examination and radiographs are sufficient to make the diagnosis.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Standard radiographs (three views—anteroposterior, lateral, and oblique) of the hand and affected digit are sufficient to determine the area of involvement (FIG 2).

Advanced imaging such as magnetic resonance imaging (MRI) and computed tomography (CT) is rarely needed.

DIFFERENTIAL DIAGNOSIS

Associated syndromes should be screened for, including trisomy 21 and Rubinstein-Taybi, Apert, and Russell-Silver syndrome.

NONOPERATIVE MANAGEMENT

Observation may be considered for duplicated digits that do not impair function of the hand.

SURGICAL MANAGEMENT

Preoperative Planning

Timing of surgery is variable.

Type B postaxial polydactyly may be removed in the office under local anesthesia, when the child is just a few weeks old.

Preaxial polydactyly reconstruction and type A postaxial reconstructions are elective procedures and are generally performed after 1 year of age and before the start of school.

FIG 1 • Type A postaxial polydactyly.

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FIG 2 • Preoperative radiograph of the patient in FIG 1 with type A postaxial polydactyly, depicting the bifacet metacarpal head.

Positioning

The patient is positioned supine on the table and the body is pulled over to the affected side. The arm is placed on a radiolucent hand table and an arm tourniquet is applied.

Approach

Deletion and reconstruction of a polydactyly is not simply an amputation. The surgeon should be aware of protecting and preserving vital structures such as the collateral ligaments and tendon insertions for

reattachment to the preserved digit.

Several approaches may be considered for the management of pre- and postaxial polydactyly. Skin incisions must take in to consideration preservation of nail folds where appropriate.

TECHNIQUE

• Type A Postaxial Polydactyly

   

   

  A racquet-type incision is made around the digit to be deleted. Skin flaps are developed. The adductor digiti minimi (ADQ) is identified and detached from its insertion and tagged.

   

  The ulnar collateral ligament (UCL) from the metacarpophalangeal joint (MCP) is released from the proximal phalanx with a large sleeve of periosteum and tagged.

   

   

  The digital nerves and vessels are identified and ligated. The duplicated digit is removed (TECH FIG 1).

   

   

  The ADQ and UCL are reinserted with 4-0 nonabsorbable suture (Ethibond). Skin is closed with absorbable suture (5-0 fast absorbing chromic gut).

   

  The hand is dressed and casted with the fingertips exposed for 2 weeks.

   

   

   

  TECH FIG 1 • Postoperative radiograph of the patient in FIGS 1 and 2 demonstrating well-aligned MCP joint.

• Type B Postaxial Polydactyly

   

  These rudimentary supernumerary digits can be addressed by simple ligature or excision.

   

  Ligature of the rudimentary digit can be accomplished via a surgical tie such as 2-0 silk or hemaclip.

   

  Application of the ligature should be tight enough to occlude the digital artery. A loose ligature will simple occlude the venous outflow and cause congestion, which can be painful for the child and prolong the time for the digit to become ischemic and fall off. A ligature placed too distal on the pedicle stalk will leave a stump and often a painful neuroma.

   

  Surgical excision can be performed in the office under local anesthetic.

   

  The child is placed in a papoose. A digital block is performed and the hand is prepped.

   

  The base of the supernumerary is pinched between the surgeon's index finger and thumb, and the stalk is cut with a pair of iris scissors. The vessel is identified and cauterized.

   

   

  The base is then sutured with interrupted locking absorbable 5-0 fast absorbing gut suture. Soft compressive dressings are applied with the tips available for the parents to observe.

   

   

   

  Dressings are removed in 3 days and bathing can be initiated after that. No follow-up is usually necessary.

   

• Wassel I or II Preaxial Polydactyly

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  Reconstruction of the duplicated thumb involving the distal phalanx may be accomplished in one of two ways.

   

  Bilhaut-Cloquet Procedure

   

  The Bilhaut-Cloquet procedure has been historically advocated for treatment of Wassel I or II thumb duplication.

   

  This involves a central wedge resection and reapproximation of the radial and ulnar structures (TECH FIGS 2 and 3).

   

  This procedure has fallen out of favor due to residual nail irregularities.

   

   

   

  TECH FIG 2 • A. Clinical photograph demonstrating conjoined nails in a Wassel I thumb. B. Preoperative radiograph. C. Postoperative photograph demonstrates normal IP alignment and nail fold following resection of small duplicated thumb.

   

  Removal of Duplicate Thumb

   

  Duplication of the thumb is rarely symmetric. One of the two duplicated thumb parts is usually larger. Deletion of the smaller thumb part is favorable.

   

  Racquet-shaped incisions are made about the thumb to excise the desired duplication. Careful attention is made to preserve the appropriate nail elements.

   

  Skin flaps are developed and the extensor tendons and flexor tendons are identified. Tendon insertions to the intended deleted digit are transected and tagged for reinsertion.

   

   

  The collateral ligament to the interphalangeal (IP) joint is elevated with a sleeve of periosteum. The duplicated digit is excised; if the head of the proximal phalanx has two facets, a chondroplasty

  (reshaping of the head) with a no. 15 blade may be necessary.

   

   

  The collateral ligament is reinserted and the joint is tested for stability. The flexor and extensor tendons are rebalanced.

   

  Skin is closed with 5-0 fast absorbing gut suture.

   

   

  Sterile dressings and a long-arm thumb spica cast are applied. Follow-up in 2 weeks for cast removal.

   

   

   

  TECH FIG 3 • Diagram depicting the Bilhaut-Cloquet procedure. (From Waters PM, Bae DS. Preaxial polydactyly. In: Pediatric Hand and Upper Limb Surgery: A Practical Guide. Philadelphia: Lippincott Williams & Wilkins, 2012:32-42.)

• Wassel Type III or IV Preaxial Polydactyly

Duplication of the thumb is rarely symmetric. One of the two duplicated thumb parts is usually larger. Deletion of the smaller thumb part is favorable (TECH FIG 4).

In most cases, the radial digit is the smaller of the two, and deletion is favored as it preserves the native UCL, which is important for pinch (TECH FIG 5A,B).

Racquet-shaped incisions are made about the thumb to excise the desired duplication. Skin flaps are developed and the extensor tendons and flexor tendons are identified. Tendon insertions to the intended deleted digit are transected and tagged for reinsertion.

TECH FIG 4 • Skin incisions for resection of Wassel III duplicate.

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The intrinsic musculature is elevated from its insertion and tagged.

The collateral ligament to the MCP joint is elevated with a sleeve of periosteum.

The duplicated digit is excised; if the head of metacarpal has two facets, a chondroplasty (reshaping of the head) with a no. 15 blade may be necessary.

If angulation of the thumb is present at the MCP joint, a closed wedge osteotomy of the metacarpal neck may be necessary to align the thumb. This can be accomplished with a small rongeur, removing bone on the radial side of the metacarpal, leaving the ulnar cortex intact, and closing the osteotomy and securing with wire.

TECH FIG 5 • A,B. Preoperative photograph and radiography, respectively, of Wassel IV duplicate thumb. C. Intraoperative photograph depicting reinsertion of intrinsic musculature following deletion of radial duplicate thumb. D. Postoperative skin closure following deletion of radial duplicate thumb.

The collateral ligament is reinserted, and the joint is tested for stability. The intrinsic musculature is reinserted (TECH FIG 5C).

The flexor and extensor tendons are rebalanced.

Skin is closed with 5-0 fast absorbing gut suture (TECH FIG 5D). Sterile dressings and a long-arm thumb spica cast are applied.

Persistent joint

angulation

• Failure to recognize deforming factors, such as misaligned tendons and

residual bony deformity

Persistent joint

instability

• Collateral ligaments must be properly reinserted.

Painful neuromas

(see FIG 3)

• Digital nerves must be identified and cut short to retract away from the

skin surface.

PEARLS AND PITFALLS

POSTOPERATIVE CARE

The first postoperative visit is 2 weeks from surgery, 4 weeks if an osteotomy is performed.

The cast is removed and digit is inspected.

Radiographs are obtained to evaluate healing in the case of and osteotomy. Pins are pulled where appropriate.

The family is instructed about wound care and scar massage.

Occupational therapy is not instituted unless there is concern for persistent joint stiffness.

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COMPLICATIONS

Irregularities with the nail fold and residual IP joint angulation are common following thumb

OUTCOMES

Outcomes from polydactyly reconstruction correction are generally good with most patients reporting good function and aesthetics.

reconstruction.

Neuroma sometimes occurs after suture ligation of postaxial polydactyly (FIG 3).

FIG 3 • Painful neuroma following suture ligation of postaxial polydactyly.

Failure to reinsert collateral ligaments or intrinsic musculature may lead to joint incompetence or weakness, respectively.

SUGGESTED READINGS

1. Al-Qattan MM, Kozin SH. Update on embryology of the upper limb. J Hand Surg Am 2013;38:1835-1844.

    

    

2. Dobyns JH, Lipscomb PR, Cooney WP. Management of thumb duplication. Clin Orthop Relat Res 1985: (195):26-44.

    

    

3. Ezaki M. Radial polydactyly. Hand Clin 1990;6:577-588.

    

    

4. Ganley TJ, Lubahn JD. Radial polydactyly: an outcome study. Ann Plast Surg 1995;35:86-89.

    

    

5. Goldfarb CA, Patterson JM, Maender A, et al. Thumb size and appearance following reconstruction of radial polydactyly. J Hand Surg Am 2008;33:1348-1353.

    

    

6. Manske PR. Treatment of duplicated thumb using a ligamentous/periosteal flap. J Hand Surg Am 1989;14:728-733.

    

    

7. Mih AD. Complications of duplicate thumb reconstruction. Hand Clin 1998;14:143-149.