Postaxial Polydactyly

November 1, 2007

This baby was born with an ulnar supernumerary digit on the left hand. This common congenital anomaly can be an isolated malformation or associated with other syndromes at birth.1-4 Although the true prevalence is unknown (because most hospitals do not report cases), the condition appears to be more common among males and African American infants.1-3 In African American infants, postaxial polydactyly is generally the result of autosomal dominant transmission. In white infants, the condition is frequently syndromic and is linked with autosomal recessive transmission.1

This baby was born with an ulnar supernumerary digit on the left hand. This common congenital anomaly can be an isolated malformation or associated with other syndromes at birth.1-4 Although the true prevalence is unknown (because most hospitals do not report cases), the condition appears to be more common among males and African American infants.1-3 In African American infants, postaxial polydactyly is generally the result of autosomal dominant transmission. In white infants, the condition is frequently syndromic and is linked with autosomal recessive transmission.1

Supernumerary digits range considerably in general size; dimensions around the base vary. Some extra digits may be fairly bulky and can contain bone.4 The defect can be postaxial or ulnar, central (in which digit 2, 3, or 4 is duplicated), or preaxial or radial (in which digit 1 is duplicated).1,3

Postaxial polydactyly is categorized as 2 types:

Type A defect--fully developed extra digit that articulates with the fifth metacarpal.

Type B defect--pedunculated, rudimentary extra digit with greater distal bulk that is small or poorly developed, or presents as a skin tag.2,3

Management depends on the complexity of the digit malformation.2-5

Ligature. Some training programs teach that suture ligation at the base of the deformity can be performed in infants with a type B supernumerary digit early in the postnatal period.5 Many pediatricians and surgeons favor this approach because it is inexpensive and relatively easy to perform. Suture ligation causes skin necrosis followed by spontaneous amputation of the leftover tissue.4

A few rare complications of suture ligation have been reported. A remnant of the digit can become enlarged after ligation and develop a central traumatic neuroma, which can divide into 5 digit-like outcroppings covered with hyperkeratotic epidermis.5 Rudimentary digits with distal bulk may result in increased necrotic tissue; those with a wider pedicle are at higher risk for infection, scarring, or imperfect amputation.4 Also, tying off the extra digit may leave a noticeable bump or nubbin with retained bone or cartilage.3 However, parents are generally satisfied with the cosmetic result, despite a residual bump.2

Surgical removal. Surgical excision may prevent the complications associated with suture ligation.3 Depending on the availability and referral patterns in your area, it may be advantageous to have the supernumerary digit surgically removed after the nursery course.

Removal of the extra digit prevents potential lifelong physical and emotional consequences.6 In children, negative psychological effects are possible by age 3 years, when they may be aware of the anomaly, and by age 7, when they typically experience close scrutiny from peers. Therefore, medical correction should be initiated early in life.1

This patient underwent surgical excision of the supernumerary digit at 9 months of age. *

References:

REFERENCES:

1.

Abel CG, McCarthy DM. Supernumerary digit. eMedicine Web site. Available at: http://emedicine.com/derm/topic692.htm. Accessed September 13, 2007.

2.

Watson BT, Hennrikus WL. Postaxial type-B polydactyly. Prevalence and treatment.

J Bone Joint Surg Am.

1997;79:65-68.

3.

Rayan GM, Frey B. Ulnar polydactyly.

Plast Reconstr Surg.

2001;107:1449-1454.

4.

Frieden IJ, Chang MW, Lee I. Suture ligation of supernumerary digits and "tags": an outmoded practice?

Arch Pediatr Adolesc Med.

1995;149:1284.

5.

Heras L, Barco J, Cohen A. Unusual complication of ligation of rudimentary ulnar digit.

J Hand Surg [Br].

1999;24:750-751.

6.

Sadove AM, Eppley BL. Pediatric plastic surgery.

Clin Plast Surg.

1996;23: 139-155.