Small Thumb

Two different thumb birth differences

The thumb is our most important digit.  In the adult, we estimate that it affects about 40% of hand function.  So, a thumb that is not fully or normally developed may really affect our abilities- whether that be strength, motion, dexterity, etc.  I have written a number of posts (See HERE) about the thumb but thought I would share a few pictures and xrays of two patients with different thumbs.

The first patient has an extra thumb.  These come in a number of different patterns.  In this case, the extra thumb is smaller and less functional than the normal thumb.  The more normal thumb is still smaller than the opposite side but has good structure and tendons. 

Thumb polydactyly (extra thumb).  The outer thumb is not normal.
Thumb polydactyly

Surgery entails removal of the extra, outer thumb and reconstruction of the main thumb.  While it is not completely normal, it should function at a high level.  The pin stays in 5-6 weeks with a cast.  Then the cast is removed, the pin is removed and therapy is begun.

Thumb polydactyly after reconstruction with excision of extra thumb, ligament reconstruction, and pinning.
Thumb polydactyly after reconstruction with excision of extra thumb, ligament reconstruction, and pinning.

The other case is an extra bone within the normal thumb.  The thumb is different than the fingers.  The fingers have 3 bones, three phalanges.  The thumb normally only has two.  A triphalangeal thumb is more like a finger with 3 bones.  Sometimes it otherwise seems like a thumb and sometimes it can rest like a finger.  With an extra bone, the thumb is longer and may be more deviated (the extra bone is often not normally shaped).  It also bends and functions differently.  We often (but not always) consider surgery for these patients. 

Triphalangeal thumb.  Note some deformity, angulation

Triphalangeal thumb x-ray. See the small bone in the middle of the two other bones.  

We removed the middle bone, reconstructed the supporting ligaments, and adjusted the tension on the tendons.  This patient should also do well with a strong, aligned thumb for the future.  Sometime motion takes time to recover but most patients have a highly functional thumb after this surgery.

Triphalangeal thumb after excision of the abnormal bone.

The patient’s other side.  More deformity with the triphalangeal thumb due to the triangular shaped bone.

These are just two examples of birth differences of the thumb.  Both of these patients should do well over the long term with strong, stable, well aligned thumbs.

Charles A. Goldfarb, MD              

My Bio at Washington University     

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