Small Thumb Ulnar Deficiency

Ulnar Deficiency- Thumb Rotation

I have posted a number of times about both ulnar longitudinal deficiency and thumb anomalies.     As previously noted, in ulnar longitudinal deficiency, we more commonly offer surgery for the hand compared to the forearm.  The forearm rotation abnormality is usually something that kids can adapt to as the shoulder offers so much compensatory motion.  The hand is, however, a bigger challenge.  I have previously posted about syndactyly and thumb rotation but I wanted to show a classic case of ulnar longitudinal deficiency in an older child.

This is a seven year old male who I have followed for years during which time he has not required any significant treatment.  He has ulnar deficiency affecting the hand.  His forearm is affected as well (absent ulna) but it does not functionally limit him.

Ulnar longitudinal deficiency with 3 fingered hand.

Ulnar longitudinal deficiency with 3 fingered hand.

This patient with ulnar longitudinal deficiency has excellent finger motion and a thumb which is somewhat under- rotated.  For that reason, we have watched him grow and develop for years and he has done well.  But over the last year he has noticed that he can’t pinch well with that thumb- specifically he can’t perform pulp-to-pulp pinch between the thumb and index finger.  The benefit of watching and waiting over the years (in this child with a moderate but not terrible deformity) is that he can better describe his frustration given his age and maturity.

Image from a non- affected patients.  Typical pulp to pulp pinch which maximizes fine motor skills such as stringing beads.

While he can pinch, as depicted below, he hopes to obtain more precise pinch.  At first glance, these pictures below show reasonable thumb function.  And, don’t mistake this message, his thumb function is good.  But he can’t quite rotate his thumb enough and he feels limited by this.  He has difficulties with certain fine motor tasks.  Many kids would not be bothered by this degree of under- rotation- but some, such as this child, are.  The general term for this issue is thumb in the plane of the fingers.  This child is somewhere between “normal” and the completely abnormal positioning.  This link shares our publication describing our experience with this issue.
Pinch with under rotated thumb in ulnar longitudinal deficiency.

Pinch with under rotated thumb in ulnar longitudinal deficiency.

And so, after many discussions with the patient, the family, and the hand therapists, we elected to proceed with a surgery to further rotate the thumb.  Sometimes we cut and rotate the metacarpal bone alone and sometimes we also add a tendon transfer.  In this case we only cut and rotated the bone.

Ulnar deficiency patient after thumb rotational osteotomy. 

Ulnar deficiency patient after thumb rotational osteotomy.

Our experience with rotational thumb osteotomy has been very good in children with ulnar longitudinal deficiency.  It improves precise function and kids and families have been pleased.

Charles A. Goldfarb, MD
My Bio at Washington University

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