Extra Digits (radial polydactyly)

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.

  2. 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.

  3. 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?

  4. 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.

  5. 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.

  6. 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.

  7. Thank you for the reply. His hand surgeon said the same thing. He sometimes uses his outer thumb to pick up things. but mainly uses the inner thumb for things like grabbing. Our surgeon ruled out merging the thumbs because it may look great right after surgery but may cause functionality issues later down the line. both of his thumbs are slightly smaller than his index finger. we are waiting to do the surgery until he turns 3 since there are reports on anesthesia hurt brain growth. Thank you so much for the reply and your time.

  8. Dr. Goldfarb i am in desperate need of your expertise. My son was born 6 weeks ago with polydactly on hands and feet as well as syndactly on all. He also has clindactly on thumbs. This is a heridaru thing that has been passed down 5 generations but with his being the most severe. My 5 year old son was born with polydactly of only feet and had the surgery here in maine where we live but they took the wrong big toe and now is left with a toe that has no bone and will need future surgeries. With my infant having more severe issues I don't want the same happening to him. Today my Dr sent a referral to the shriners children's hospital requesting you. I truly hope you will accept that referral as you are my only hope for my son. Thank you for reading this.
    Jayme Gibson

  9. Majied,
    Thank you for the question. There is no 'best age' and there are several factors to consider that your doctor can help with. I usually operate at approximately 18 months (but certainly sometimes earlier or later) for two main reasons.
    First, a larger hand is technically easier to work with surgically. The hand doubles in size from birth to 2 years of age and then almost doubles again. And second, anesthesia becomes somewhat safer with age.

  10. Surgery can be done at an older age but should be considered more carefully. Obviously, you have been living with this for 19 years- make sure you know why you want to think about surgery and how the surgery could change the way you use your hand.

  11. Hi Dr
    My daughter is turning one this month and she has polydactyl thumb on her left hand. Her outer thumb seems to be the one that has all the muscles and able to grab on to things. The surgeon here are thinking of removing the inner thumb and retain the outer thumb as that is one that is functioning but they are both the size of her pinky. Is there anyway to aesthetically retain a similar size to her other normal thumb?

  12. Hello. Good luck with surgery. It is rare for the outer thumb to be more functional but occasionally that is the case. This scenario for surgery can make the appearance more challenging as well. There is no great way to combine the thumbs for size (the so called Bilhaut procedure)- research has shown that this procedure does not work as well as excision and reconstruction. The goal is a well aligned, stable thumb, ideally also with good motion and hopefully that can be accomplished for your daughter.

  13. Hi. This is great info. My 3 yr old son has surgery coming up. On his left hand the thumb looks similar to this. The right hand thumb is only double at the tip. Because of insurance change we had to change doctors and I’m nervous. The original doctor performed my older two kids surgeries (feet) and my 3 yr olds feet. I hate we had to switch. I sent you an email

  14. Hi. My son is 7.5 months old and was born with radial polydactyly, an extra protruding thumb on his right hand. I’m super worried as a father. We are planning on having surgery in a couple of weeks. Can I contact you and send you the X-ray to get your thoughts? Is that ok?

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