Sunday, January 11, 2015

The Extra Thumb

An extra thumb, or radial polydactyly, can represent a difficult problem in congenital hand surgery.  The difficulty is that each child with an extra thumb is somewhat different.  There are certainly patterns (as we see with the Flatt Classification system) but not every thumb fits this classification system.  Zuidam and all (under the leadership of Steven Hovius in Rotterdam, The Netherlands) added to our understanding of radial polydactyly with these additional thoughts on the Topic.

The goals for reconstruction of the extra thumb are well accepted- a stable, straight thumb that functions well and looks good.  Patients don't like crooked thumbs (and nor do we) and no one likes thumbs that are not stable either (see our Publication). A thumb without stability is weak for pinch.  The surgeon's job is more difficult when the joints are not straight and the bones are not straight.  These situations require a more complex reconstruction of bone, joint, tendon, and muscle insertion.  Here is one such case of a Type IV extra thumb- which means the duplication is at the level of MCP joint with two proximal and distal phalanges (as you will see below).   In this case we had to narrow the metacarpal bone, reconstruction the ligament, and reconstruct the tendon insertion but did not have to cut and re- align the bones.

Radial polydactyly, type IV.  Not the deviation of both thumbs.

Radial polydactyly, type IV.  Not the deviation of both thumbs.  Palm view.

Radial polydactyly, type IV.  Not the deviation of both thumbs.  X- ray.

The outside thumb, the radial thumb, is removed to allow the best thumb (which is generally but always the inside thumb).  
Planned incision for radial polydactyly surgery.

Planned incision for radial polydactyly surgery.

Surgery allows straightening and stabilization to a now straight thumb.

The green sutures indicate where the ligament and the tendon were reconstructed for radial polydactyly.

After radial polydactyly surgery.

After radial polydactyly surgery.  Note that we avoid straight skin incisions as they can tighten over time.
Charles A. Goldfarb, MD
My Bio at Washington University


  1. thanks for the post. my son was born with an extra thumb. for him, it seems the outer thumb is much stronger than the inner thumb. and the outer thumb is more also more bent than the inner thumb. he is 2 month old now, both of his thumbs are the size of his pinky. do you know if this will stay that way as he grows older? we are getting concerned that after the surgery the thumb will be much smaller.

    1. Congratulations on the birth of your son. Your question is interesting and challenging. The vast majority of the time, the inner thumb is preserved as this preserves a key ligament. But sometimes, the outer thumb is maintained and sometimes the best parts of both thumbs are merged (either side to side or longitudinally). Your son's situation is more challenging than most. In addition, the small size is a challenge. While the thumb is critical for activities, a high level of functioning is based on position and stability. Size may be important for appearance but is less important functionally (unless really small and, more importantly, really short). Again, sometimes the two thumbs can be merged.
      Good luck. Your situation makes it more important to seek and experience congenital hand surgeon.

  2. Thank you for sharing your post, Dr Goldfarb. It helped me understand my baby daughter's condition & surgery.

    She underwent thumb surgery 2 years ago, during which her 2 thumbs were merged for stability. Her inner thumb was deemed too small and would not be able to carry heavy loads.

    Now that she has turned 3 and is very articulate(!), she has informed that her right thumb is damaged as she can't bend it. Is this a common phenomenon? Can it be rectified? Her thumb is also significantly larger and misshapened, i presume with the greater bone mass due to the merger of 2 thumbs, this is inevitable?

    1. Lena,
      Thank you for the question. First- it is very difficult to regain motion (and is not an uncommon issue). The good news is that function can be outstanding even without motion. More problems develop with a lack of stability or deformity. Second, the size and shape are not uncommonly affected and can sometimes be corrected. I hope this is helpful.

  3. Hello Mr. doctor
    My name is Marian Mihai and I am the father of a boy aged 1 year and 8 months who was born with polydactilie left wing.
    Our boy was operated in Romania in June 2017, and after the operation he wore gypsum for 30 days.
    One week after removing the gypsum, the operated finger curved inward.
    I decided to write these lines in the hope of helping you.
    I know that in the past a blog-like situation was posted on our blog.
    Considering your experience, please support me with advice on whether it is necessary to wear a system (orthosis) to keep the child's finger in the correct position after surgery.
    The orthopedic doctor informed us that in Romania there is no such device of contention for keeping the finger operated in the correct position.
    To better understand our situation, I can send you photos before and after surgery.
    Sorry for my bad english.

    1. Marian. Thank you for writing. I don't find orthoses or splints to be helpful as surgery usually solves the problem of an extra digit (and the surgery may be more than just removing the extra digit). I hope this helps.