Thumb position and the 3 digit hand

I have posted on thumb rotation and if you search the blog, you will find a number of posts on ulnar longitudinal deficiency.  Scrolling through the pictures, a pattern begins to develop in these kids with ulnar longitudinal deficiency- that is, many of the kids have a well developed thumb and 2 very good fingers.

When we think about ulnar longitudinal deficiency, we think mainly about the forearm.  And we should as deficiency of the ulna with its associated tendon and muscle limitations are important.  But from a functional standpoint, as Dr Manske taught us so many years ago with this classic article, the hand and thumb specifically are very important.  Dr Manske focused on the thumb web but, as we later demonstrated in this article, the rotation of the thumb is important also.  Because if the thumb is in the plane of the fingers, some function of the thumb is lost and pinch is neither strong nor precise.

This child with ulnar longitudinal deficiency has a thumb and 2 fingers.  All are well developed.  But the position of the thumb is not great for function.  The family is considering a rotation of the thumb to allow improved function.

Ulnar longitudinal deficiency with a thumb and 2 fingers.  Note the position of the thumb.

Ulnar longitudinal deficiency with limited pinch.  No that the child is pinching with the side of the the thumb, not the 'meaty' pulp which gives the best strength and function

I posted these pictures and this brief discussion simply because I though the pictures were so powerful.  This is a challenging situation because the child functions well.  However, I believe that he can function better with more precise thumb function with surgery.

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