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The Journal of Bone and Joint Surgery 79:65-8 (1997)
© 1997 The Journal of Bone and Joint Surgery, Inc.

Postaxial Type-B Polydactyly. Prevalence and Treatment*{dagger}

BRENT THOMAS WATSON, M.D.{ddagger} and WILLIAM L. HENNRIKUS, M.D.§, SAN DIEGO, CALIFORNIA

Investigation performed at the Department of Orthopaedic Surgery and Clinical Investigation, Naval Hospital, San Diego


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
A prospective screening program of 11,161 newborns identified twenty-one infants who had postaxial type-B polydactyly (a prevalence of one in 531 live births). Sixteen infants (76 per cent) had bilateral postaxial type-B polydactyly. Eighteen infants (86 per cent) had a family history of the anomaly. The racial prevalence was one in 143 live births of black infants and one in 1339 live births of white infants. The duplicated small fingers were treated in the newborn nursery with suture ligation at the base of the pedicle. One infant had a second procedure to remove a blackened digit that remained firmly attached one month after the initial treatment. No other complications occurred. Fifteen patients (twenty-eight fingers) were re-examined at an average age of twenty months (range, twelve to thirty-seven months). Twelve fingers (43 per cent) had a residual bump, with an average diameter of two millimeters (range, one to six millimeters). Despite the residual bumps, all of the parents were satisfied with the cosmetic result.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Postaxial polydactyly, or duplication of the small finger, is categorized as type A (the extra digit is fully developed) or type B (the extra digit is rudimentary and pedunculated)10 (Fig. 1).



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  		Fig. 1 Postaxial type-B polydactyly in a newborn.

 
Duplication of the small finger is genetically determined. When it occurs in isolation, it is usually inherited in the dominant mode. When there is an associated syndrome, the duplicated digit is often inherited in the recessive mode2.

To the best of our knowledge, the true prevalence of postaxial type-B polydactyly has never been established by a prospective study. Estimated prevalences are probably inaccurate because many rudimentary digits are tied off by pediatricians and obstetricians in the nursery without documentation1,2,14. Although the practice of tying off for the treatment of postaxial type-B polydactyly in the newborn nursery is common2,9,13, we are not aware of any reports of the results and complications of such treatment. In addition, although some authors have cautioned that exsanguination can result from this treatment2,7,9,14, to our knowledge no case report documenting this complication has been published.

The purpose of the present study was to determine the prevalence of postaxial type-B polydactyly through the use of a universal newborn screening program and to report the results and complications of treatment with suture ligation in the nursery.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
From January 1992 until May 1995, 11,161 consecutive infants were examined during a newborn screening program for instability of the hip. Of these infants, 6694 were white, 2008 were black, 1618 were Asian, 589 were Hispanic, and 252 were other or mixed races. In addition to the examination of the hip, a general orthopaedic screening, including examination of the hands for polydactyly, was performed on each child. All abnormalities were recorded in a logbook. A family history of postaxial type-B polydactyly and any associated anomalies were recorded.

Infants who had postaxial type-B polydactyly were treated in the newborn nursery. The pedunculated digit was ligated at its base with use of undyed 2-0 Vicryl suture (polyglactin; Ethicon, Somerville, New Jersey). Local anesthesia was not used. Patients were re-examined in the pediatric orthopaedic clinic at the age of one to two weeks (Fig. 2).



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  		Fig. 2 Necrosis of the rudimentary digit just before autoamputation.

 
The parents of fifteen children (twenty-eight fingers) were contacted by the junior one of us (B. T. W.), and the patients were re-examined at an average age of twenty months (range, twelve to thirty-seven months). The range of motion of the small finger was measured with use of a finger goniometer and compared with that on the contralateral side. The size of any residual bump was measured in millimeters. Residual deformity from the treatment of the polydactyly was rated on a 5-point cosmetic scale, with 1 point given for a normal digit without a noticeable scar or bump; 2 points, for a small, barely noticeable scar; 3 points, for a small bump (maximum diameter, less than three millimeters); 4 points, for a large bump (maximum diameter, three millimeters or more); and 5 points, for a scar or bump that prompted the parents to request a revision operation for cosmetic reasons.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Twenty-one newborns who had postaxial type-B polydactyly, which was bilateral in sixteen of them, were identified. Thus, the screening revealed a prevalence of one in 531 live births. Twelve infants (57 per cent) were boys, and nine (43 per cent) were girls. Fourteen patients (67 per cent) were black, five (24 per cent) were white, and two (10 per cent) had one black parent and one white parent. No Asian or Hispanic children were found to have postaxial type-B polydactyly. The prevalence of postaxial type-B polydactyly was one in 143 live births of black infants and one in 1339 live births of white infants.

Eleven of the sixteen patients who had bilateral polydactyly were black, and five were white. Eighteen (86 per cent) of the twenty-one infants had a family history of postaxial type-B polydactyly. Fourteen were black and four were white. No syndromes were identified in any of the infants in our study.

There was one complication of the treatment with suture ligation. One child needed a second procedure, in the operating room, to remove a blackened digit that had not fallen off one month after the original ligation. That digit had had a large base. The parents of the remaining twenty patients reported that the average time for the extra digit to fall off after suture ligation was ten days (range, four to twenty-one days). No infections or bleeding complications occurred.

The range of motion of all involved digits of the fifteen children who were re-examined at an average age of twenty months was equal to that on the contralateral side, and there were no angular deformities. No finger had a perfectly normal cosmetic appearance. Sixteen fingers (57 per cent) had a small scar that was barely noticeable (Fig. 3). Nine fingers (32 per cent) had a small bump, and three fingers (11 per cent), in two children, had a large bump (Fig. 4). No parent requested a cosmetic operation for their child. Revision was offered to the parents of both of the children who had a large bump, and it was declined. The average diameter of the residual bump was two millimeters, with the largest bump being six millimeters in diameter.



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  		Fig. 3 This patient had a small, barely noticeable scar (arrow) at the time of the most recent follow-up.

 


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  		Fig. 4 This patient had a large bump at the time of the most recent follow-up.

 


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Mellin, in a study of 5735 infants who weighed more than 500 grams, and other authors2,4,11, concluded that polydactyly is the most common congenital anomaly of the hand in black infants and that syndactyly is slightly more common than polydactyly in white infants11. Frazier, in a study of 120,127 records of live births, and other authors5,8,12, reported that postaxial polydactyly is about ten times more common in black infants than in white infants. This ratio was confirmed in our study, which revealed a prevalence of one in 143 live births of black infants compared with one in 1339 live births of white infants. Although we did not find postaxial type-B polydactyly in any of the 1618 Asian or 589 Hispanic infants that were examined, polydactyly has been reported in all countries and races2.

Eighteen of the patients in our series had a parent who also had postaxial type-B polydactyly. This finding confirms a dominant mode of inheritance in most individuals1,14. Bilateral duplication of the small finger has been reported more commonly in black infants1,9. In our study, eleven black and five white infants had bilateral involvement. Postaxial polydactyly can be associated with a variety of syndromes1,2,6,9, but no syndromes were identified in our series.

The treatment of postaxial type-B polydactyly is controversial. It has been recommended that suture ligation at the base of the pedicle be performed while the newborn is in the nursery1. The result is necrosis and spontaneous amputation. No bleeding complications were reported with this technique1. Other authors have admitted that suture ligation is commonly practiced but have advised caution because of the possibility of exsanguination2,7,9,14. Of these authors, Flatt as well as Tachdjian did not cite a reference for a case of exsanguination and Simmons as well as Wright and Jobe referenced Flatt's textbook when warning about this complication. Despite his admonition about a rare death from bleeding, which was reported to him by another surgeon (as one of us [W. L. H.] learned in a discussion with Flatt), Flatt still recommended suture ligation for the treatment of postaxial type-B polydactyly. In contrast, Tachdjian recommended division of the pedicle with a scalpel and coagulation of the stump with electrocautery, and Wright and Jobe advocated excision and closure of the skin with a tourniquet in place and inflated. Presumably, both recommendations for operative excision include the use of anesthesia and the performance of the procedure in the operating room. Simmons recommended that, when the parents decline suture ligation in the nursery, elective excision should be performed with the use of general anesthesia when the child is six months old.

The cosmetic result following treatment of postaxial type-B polydactyly with suture ligation has not been previously reported, to our knowledge. Flatt stated that tying off the duplicated digit produces a blackened stump that drops off, leaving an almost invisible scar. We found such a result in sixteen of the twenty-eight fingers that we examined after the patient was one year old. Twelve fingers had a noticeable bump, but no parent wanted their child to have a revision for the bump or scar. In fact, many of the parents had a residual bump on their own small fingers as a result of treatment of the same disorder as an infant. Before treatment is carried out, parents should be informed that the procedure always results in a small scar and that 40 per cent of patients have a residual bump.

In conclusion, we believe that suture ligation at the base of the pedicle is a simple, safe, and effective treatment for postaxial type-B polydactyly.


   Footnotes
 
*Although none of the authors has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article, benefits have been or will be received, but are directed solely to a research fund, foundation, educational institution, or other non-profit organization with which one or more of the authors is associated. Funds were received in total or partial support of the research or clinical study presented in this article. The funding source was Clinical Investigation Program S-93-094, Naval Hospital, San Diego, California.

{dagger}The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of Defense or the United States Government.

{ddagger}Department of Orthopaedic Surgery and Clinical Investigation, Naval Hospital, San Diego, California 92134-5000.

§Department of Orthopaedics, Valley Children's Hospital, 3151 North Millbrook Avenue, Fresno, California 93703.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Dobyns, J. H.; Wood, V. E.; and Bayne, L. G.: Congenital hand deformities. In Operative Hand Surgery, edited by D. P. Green. Ed. 2, vol. 1, pp. 479-490. New York, Churchill Livingstone, 1988.

  2. Flatt, A. E.: Extra fingers. In The Care of Congenital Hand Anomalies. Ed. 2, pp. 292-316. St. Louis, Quality Medical Publishing, 1994.

  3. Frazier, T. M.: A note on race-specific congenital malformation rates. Am. J. Obstet. and Gynec., 80: 184-185, 1960.[Medline]

  4. Kromberg, J. G., and |and |Jenkins, T.: Common birth defects in South African blacks.. South African Med. J., 62: 599-602, 1982.

  5. Mellin, G. W.: The frequency of birth defects. In Birth Defects, pp. 1-17. Edited by M. Fishbein. Philadelphia, J. B. Lippincott, 1963.

  6. Ruby, L., and |and |Goldberg, M. J.: Syndactyly and polydactyly. Orthop. Clin. North America, 7: 361-374, 1976.[Medline]

  7. Simmons, B. P.: Polydactyly. Hand Clin., 1: 545-565, 1985.[Medline]

  8. Simpkiss, M., and |and |Lowe, A.: Congenital abnormalities in the African newborn. Arch. Dis. Child., 36: 404-406, 1961.[Free Full Text]

  9. Tachdjian, M. O.: Polydactyly. In Pediatric Orthopedics. Ed. 2, pp. 240-257. Philadelphia, W. B. Saunders, 1990.

  10. Temtamy, S., and |and |McKusick, V. A.: Synopsis of hand malformations with particular emphasis on genetic factors. Birth Defects, 3: 125-184, 1969.

  11. Temtamy, S. A.,, and |and |McKusick, V. A.: Polydactyly as an isolated malformation. Birth Defects, 14: 364-392, 1978.

  12. Ventruto, V.; Theo, G.; Celona, A.; Fioretti, G.; Pagano, L.; Stabile, M.; and |and |Cavaliere, M. L.: A and B postaxial polydactyly in two members of the same family. Clin. Genet., 18: 342-347, 1980.[Medline]

  13. Woolf, C. M., and |and |Myrianthopoulos, N. C.: Polydactyly in American Negroes and whites. Am. J. Hum. Genet., 25: 397-404, 1973.[Medline]

  14. Wright, P. E., and Jobe, M. T.: Congenital anomalies of the hand. In Operative Pediatric Orthopaedics, p. 301. Edited by S. T. Canale and J. H. Beaty. St. Louis, Mosby-Year Book, 1991.


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