The condition of a child born with two thumbs has many, many names but most commonly, we call it radial polydactyly, thumb duplication, or split thumb. While all are utilized, radial polydactyly is the medical term and split thumb is appropriate as both thumbs are smaller than the other thumb. I have posted about radial polydactyly previously as can be seen HERE.
We have learned over the years that surgical reconstruction of the extra thumb is much more than removing one of the thumbs. The remaining thumb requires stabilization and often straightening. This can be tricky and, I believe, is best accomplished by a surgeon with experience in treating these problems- really the more experience, the better. Even then, sometimes a second surgery may be required as the child ages. This has been discussed over the years but a nice long term follow- up study from Dallas, as detailed HERE, reports on 43 kids at an average follow- up of 17 years. These late surgeries were for different reasons but a crooked thumb was often the issue.
The surgical goals for radial polydactyly are to
1) Remove the extra thumb
2) Maintain the ‘better’ thumb. Typically that is the one closer to the hand but not always
3) Stabilize the thumb (i.e., make sure the ligaments are good)
4) Align the thumb (i.e., make sure the bones are straight)
We typically add a temporary metal pin to protect the surgery during the first 5 weeks when the child is casted. Cast and pin are removed at the first visit after surgery.
Here is an example of the early outcome after reconstructive surgery for radial polydactyly. This child was not as complex as some but still a challenge. One thumb was clearly larger and it was also crooked, requiring straightening of the bone at the time of surgery. Both the family and I are pleased at this point but we will follow the child over time to assure that the thumb stays straight and functional.
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| Radial polydactyly before surgery. Note that the large thumb is somewhat crooked. |
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| Here is the side view of the thumb after surgery for radial polydactyly. Not the subtle scar. |
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| Top view of the thumb after radial polydactyly reconstruction. The thumb is straight. |
Charles A. Goldfarb, MD
My Bio at Washington University
congenitalhand@wudosis.wustl.edu