Thursday, August 16, 2018

Unusual "Extra" Finger

I have posted many times on polydactyly- both on the thumb side and the pinky side- as can be seen HERE.  The following patient demonstrates an unusual presentation of what initial appears to be an extra finger, an ulnar polydactyly.  But, as a quick 'count' confirms, there are only 4 fingers with a thumb.


Ulnar deficiency with apparent polydactyly

Ulnar deficiency with apparent polydactyly, palmar view
The xrays are very helpful in understanding this patient's hand.  There is one thumb and four fingers BUT, there are only 4 metacarpal bones in the hand instead of the normal 5.  This is an ulnar deficiency of the hand as demonstrated by the lack of a fifth metacarpal.  The 4th metacarpal is wider than normal.  I have written about this uncommon form of ulnar deficiency HERE.  This is a scientific article sharing our experience.
Ulnar deficiency affecting the hand.

Occasionally the 4th metacarpal is wide enough to allow a surgery to split it to support both the ring finger and the pinky finger.  In this case, however, I did not feel that the metacarpal was wide enough to consider such a reconstruction.  

In addition, in this patient, the pinky finger was tethering or limiting the more normal ring finger, decreasing its motion and causing deformity.  The patient's family was initially hesitant to excise the pinky finger.  It is always difficult to make this decision despite the deformity.  With time, the limitations caused by the pinky finger to both function and appearance were appreciated and the family requested surgery to remove the finger.  Here are pictures and xrays only 6 weeks after surgery.  Function and appearance are excellent and the patient and family are both very pleased.  The function (motion and alignment) of the ring finger are much improved. 

After surgery for pinky excision in ulnar deficiency.  (The picture is a little hard to interpret because the index finger is bent).


Xray after pinky finger excision in ulnar deficiency.

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

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