Sunday, April 7, 2019

Symbrachydactyly- The typical form defined

I have posted a few times on symbrachydactyly and those posts can be found HERE.  In addition, there are several reasonable summaries at other sites including this free ARTICLE from a friend and colleague, Michelle James.  Many hospital sites also offer a brief summary of the diagnosis.  In my practice, it is not common that patients come to the office with a diagnosis of symbrachydactyly.  In fact, that almost never happens.  Most patients are labeled as having amniotic band or constriction band syndrome incorrectly.

While there are a few classifications of symbrachydactyly, this one, to me, summarizes the different forms best:
  1. short finger
  2. cleft type (thumb and small finger present)
  3. peromelic (nubbins)
  4. monodactyly (only the thumb present)
  5. wrist bones present (but nothing more distal)
  6. wrist bones absent (ie, arm ends at the end of the forearm)
  7. transforearm (amputation at mid forearm level)

For this discussion, I would like to focus on the short finger type of symbrachydactyly (Type 1).  That is, patients with a thumb and four fingers but with shorter digits than expected (brachydactyly meaning short finger)  The size of the digits can vary dramatically and can include a failure of some of the bones to form or shorter bones than expected.  These patients also have webbing between the fingers (thus the name symbrachydactyly rather than just brachydactyly).

These two images help to show a relatively mild form of symbrachydactyly with short digits and a surgically corrected webbing between the fingers.

Symbrachydactyly after deepening of the spaces between the fingers.


Symbrachydactyly x-rays showing short middle phalanges

These x-rays demonstrate short middle phalanges which account for the overall short digits.  See the red arrow on the middle phalanx.  The metacarpals (in the hand) are normal, the proximal phalanges are normal, and the distal phalanges are normal or near normal.  But the middle phalanges are short, as expected, in this mild form of symbrachydactyly- thus making the overall finger length less than expected.  While the digits are short, function is typically excellent and surgery to address the length is not recommended.  The only surgery for patients with this type of symbrachydactyly is what has been provided for this patient- a correct of the syndactyly or webbing.

Charles A. Goldfarb, MD
My Bio at Washington University
congenitalhand@wudosis.wustl.edu

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