Finger Deformities

Clasped Thumb.

Clasped thumb is an uncommon diagnosis in which the thumb is held in the palm.  While there are several potential reasons for this positioning, in many cases it is simply due to a delay in muscle development of the thumb extensors.  Over time, those muscles (EPB and EPL) can (but may not) strengthen sufficiently to allow normal function.  Our job during the interval between diagnosis and recovery is to keep the thumb flexible so that if the muscles do develop, the thumb can straighten.  This mainly entails therapy to straighten the thumb to stretch it and sometimes we use splints to do the same.  Occasionally, a soft Benik Splint can help place the thumb in a better position to allow function.

Often clasped thumb affects both sides but the recovery may not be equal.  In the patient below, the right side was worse from early childhood.

Clasped thumb with the fingers straightened.

Over time, in this patient, the left side recovery but the right side did not.
Continued clasped thumb in a 2 year old.

This video demonstrates that the left thumb has recovered nicely but the right still has notable limitations.  We will continue to discuss surgery while giving this clasped thumb a bit longer to recover on its own.
I have previously blogged about congenital clasped thumb- see HERE.  I hope this video sheds light on the diagnosis.  
A couple of further thoughts on congenital clasped thumb.
1)  Surgery can be helpful.  If the patient fails to gain the strength to straighten the thumb, surgery can improve function.  Typically we rearrange tendons to add another muscle unit to help the straightening process.  We do want to allow sufficient time for the thumb to gain strength and recover on its own, but this does not always occur.
2) Generally the diagnosis of clasped thumb is clear but not always.  Other diagnoses must be considered including an association with syndromes or even things like cerebral palsy (CP).  CP can have a thumb in palm deformity but it is related to tight muscles (spastic muscles) rather than weak extensor muscles.
Clasped thumb is a diagnosis that can have a very favorable outcome with or without surgery.  
Charles A. Goldfarb, MD

My Bio at Washington University


  1. Dr. Goldfarb, thanks for writing this blog – what a great resource! My 3 month old has preaxial polydactyly as well as a clasped thumb on one of her hands. How common is it to have both conditions?

  2. M,
    Thank you. I am glad the blog is a good resource. It is unusual to have both conditions. Clasp thumb is often bilateral and, in my experience, is usually not associated with conditions like polydactyly. However, radial polydactyly can have thumbs that don't straighten fully although, in my experience, this is typically different than clasped thumb.

    I certainly hope you are being cared for by an experienced congenital hand surgeon. Good luck.

  3. Hi Dr. Goldfarb

    My daughter is almost 14 months and has had congenital clasped thumb since birth. She has seen an ortholedic and neurologist but no-one seems to be concerned. She is reaching all her developmental milestones but still struggles with eating solids as she prefers her bottle. She has had two different splints but neither have improved the mobility of her thumbs. Her right thumb is worse than the left similar to your patient in the video. She is able to actively abduct her thumbs to grab or hold items but once she drops the items, her resting position is with both thumbs tucked in. How is your patient now? Is there anything I could do or explore further?

    Thank you

  4. Shaunta,
    Thank you for writing. I am glad that your daughter is doing well overall. The fact that she can position her thumbs to grab bigger objects (if I am reading this correctly) is a good sign. With additional time, her thumb strength will improve and the thumbs will likely rest in a better position. We typically just keep up the exercises and stretching and splinting until around 2 years of age. If she still has limits at that age, surgery can be considered. Thankfully, it is not usually required. Good luck.

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