Triphalangeal Thumb

The normal thumb has two bones- 2 “phalanges”- which makes it different from the three bones of the fingers.  Occasionally, we see a thumb with 3 bones- 3 “phalanges”- and we call it a triphalangeal thumb.  I have previously blogged about different aspects of the triphalangeal thumb– 5- finger hand and another on the Five finger hand.  Also, sometimes, the triphalangeal thumb is part of radial polydactyly when there is one triphalangeal thumb and one more typical thumb with two phalanges.

I wanted to share a case in which there was a single triphalangeal thumb.  This case is somewhat typical in that the extra bone is a really small, triangular shaped bone.  This bone causes a deviation of the thumb and that is usually the reason that the family seeks help. Surgery, as shown below, is reliable in straightening the thumb but does not always restore full motion.

Triphalangeal thumb, crooked due to the extra triangular shaped bone.

Another view of the Triphalangeal thumb, crooked due to the extra triangular shaped bone.

X-ray of the triphalangeal thumb.  There is a really small triangular bone between the main 2 thumb bones.

Another view of the  X-ray of the triphalangeal thumb.  There is a really small triangular bone between the main 2 thumb bones.

This extra bone causes the thumb to be crooked and can also limit motion.  For both reasons, the patient may be taken to the operating room to remove the extra bone and tighten the joint.  A pin is placed to allow the soft tissues to heal.

This is the extra bone after removal.

Triphalangeal thumb after removal of the extra bone.  The thumb is straight once again.

Charles A. Goldfarb, MD
My Bio at Washington University


  1. Hi there. I've just seen this article. My 6 half year olddaughter is currently going through recovery open appointment discard after having 'huba transfer' for her right triphangular thumb movement and the base has improved but is not straight and still can not move the tip of her thumb and will undergo her 2nd for left in the next year's time. It's says in this article the thumb can be straightened. Will that enable thumb tip movement? Thank you. A Concerned mother.

  2. Hello. Thanks for the question. I believe she had a Huber transfer which is a muscle transfer in which the abductor digiti minimi is transfered to power the thumb. That surgery is done when the muscles of the thumb are weak or absent preventing the positioning of the thumb for ideal function. Thumb tip movement is dependent on a number of factors including the presence and independence of the muscles that bend and straighten the thumb (vs the thumb muscles in the palm). So, the surgery you have had will not help tip movement but should help position the entire thumb. I hope that helps and makes sense. Good luck.

  3. Hi Dr. Charles.My 1 year old daughter has Triphalangeal Thumb on both of her thumbs (more pronounced on left than right).We have scheduled the surgery to remove the extra triangular bone next week.Right now we see that her basic motor skills are fine and the movement of thumb tip is also not a problem.However we do see the discomfort when trying to hold small things.Will this surgery hinder her thumb tip movement in the future.Also is it the right time to have the procedure done with she being 13 month old or should we wait for another few years so that she can withstand the pain.Thank you.

  4. Avinash, thank you for the question. Good luck on the surgery for removal of the extra triangular bone. I have not seen this cause pain or discomfort- in fact, I usually would state the opposite- this does not seem to cause pain.

    The surgery can lead to some stiffness in the thumb. This is due to removal of the bone and its affect on the joint above and below the extra thumb. However, function is usually excellent.

    Finally, I usually wait until at least one year of age and often 18 months. But, as long as the surgeon feels comfortable with the size of the bone to be removed, surgery at this age seems reasonable.

    Good luck.

  5. In what ways does this condition hinder motion? My grandfather, father, I, and my daughter all have both thumbs like this and have no problems whatsoever. Thank you.

    1. I’m just finding this article and I agree. Me and my son also have it and never received any surgery for it and they are fully functional… crooked or what may be considered “deformed” but, they don’t hinder our lives in any capacity.

      1. Thank you. Your experience is helpful for others.

        However, not all of those affected would necessarily agree- sometime function is affected and the angulation is unacceptable.

  6. Doug,
    Thank you for the question. Different types of triphalangeal thumb affect different people differently. Some, like you and your family members do great while others have decreased thumb motion, possibly deformity, and decreased function. Interestingly, I have had some people with great motion complain about the extra joint creating an awkward motion.

  7. Hello, I think I have this condition on both my hands, but I have never had any pain or discomfort associated with it. Is there any benefit to having the extra knuckle removed anyway? Is there a specialist I could send a picture to?

    Thank you,

  8. My 21 yr old daughter just had a hand xray this week and it showed a extra triangular shape bone exactly like the above xray picture. The doctor kept pushing on it and asking if it hurt. It doesn't and hasn't caused a visual deformity. Is it possible to have this with no future issues? Dr. didn't know what it was.

  9. I have this and it has always been a burdon… I was always teased because the tip of my finger doesn't bend forward on both sides.. also it hurts alot when i write or type… Do you have a general idea of the price ranges for this surgery?

  10. Hello Mariah. I am sorry this has been a burden for you. Surgery won't help motion but could help alignment and may help with the discomfort. Cost for surgery is impossible to predict as it is based on so many factors including insurance, hospital, etc. Good luck.

  11. Hello Dr. I have the same issue and as the image shown above. I have it on both hands but my right thumb is more pronounced. The left one is hardly noticeable. I was also born with an extra phalanges next to the right thumb but that was removed at a very early age so I have no recollection of that. (I found out quite old actually thought a picture, lol). My mother has it and a sister and her daughter. None of my 3 boys were born with it thought. Im happy for that as it has been more of a social headache for me growing up. I work with prints a lot so im always very conscious about it when working with people. Do you recommend anyone who can perform this surgery in the Central Florida area. I have never had pain or discomfort really. Thank you for your time!

  12. Thank you for writing. I cannot give you a complete answer without more information regarding xrays and your specific anomaly. It may be that a correction of angulation would help. Some 'adult' hand surgeons might be helpful for you but ideally there would be a hand surgeon who takes care of both adults and kids born with birth anomalies. Feel free to contact me by email with additional specific questions: .

  13. Hello. I don't know of this appropriate to ask. My 3 year old daughter was born with this condition on both thumbs. Her function isn't affected but we have been told that as she gets older it will be more more look of the the as they both have a bend inwards. We have been offered surgery for her before she starts school but my husband and I are both on the fence about it. I have this as well and had my thumbs operated in. One over corrected and the other now looks more finger like.
    I have been trying to find pictures of adult tripalangeal thumb wuth a bend that have not been treated so that we can have an idea of what it could looking amd that .as have a bearing on our decision. Thanks in advance.

  14. Hello. Thank you for the question. I have spoken to a number of parents with triphalangeal thumbs who were not treated. Most of those (granted, these were the families in my office) wished to proceed with surgery for their affected children. There is no right or wrong answer. Surgery is not perfect, but in my experience, has been helpful for children. I hope this perspective is helpful. And, of course, the experience of your surgeon matters to outcomes.

  15. Hi grandma, dad, and I have crooked thumbs. It’s a genetic legacy. There is no precedent in our great dynasty except for one of my cousins. I am a member of a Turkish family that immigrated from Balkan Europe. Although this finger curvature is an anatomical defect, it is likely to be genetically related to other human populations and countries. Do you have any research on genetic factor? If so, I wish you (as children of our common ancestors) to meet people who will confirm this very interesting situation and gather members of such an elite group in a network.

Leave a Reply

Your email address will not be published. Required fields are marked *