Friday, April 24, 2015

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 thumb5- 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.

    1. 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.

  2. 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.

    1. 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.

  3. 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,

    1. Whitney,
      I am glad that you do not have pain. If you are functioning well and don't have other issues, I would not recommend surgery. But if you notice challenges, the knuckle removal can shorten the thumb and, for some, will improve function. A congenital hand surgeon would be helpful. I can be reached at

  4. 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. 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.