KidsMD Health Topics

Thumb Hypoplasia/Aplasia

  • Thumb hypoplasia, also commonly called hypoplastic thumb, means that your child’s thumb is unusually small or underdeveloped. Thumb aplasia means that your child’s thumb is missing altogether.

    In general, there are five types of thumb hypoplasia or aplasia:

    • Your child’s thumb is slightly smaller than normal, but all of its structures — the bones, tendons, ligaments, muscles and joints — are normal.
    • Your child’s thumb is small and there are often minor abnormalities in the tendons and muscles within the thumb.
      • The middle joint of the thumb is unstable, causing the thumb to wobble. The web space between the thumb and index finger is tight and restricts movement.
      • The bones of your child’s thumb are abnormally small.
    • There are abnormalities in many of the thumb's muscles along with a range of problems in the joints of the thumb and an abnormal tight web space between the thumb and index finger.
    • Your child’s thumb is "floating" with no bony support and is attached to the hand by only skin and soft tissue.
    • Your child’s thumb is missing.

    hypoplastic thumb

    Partners in care

    If your child has mild thumb hypoplasia, she may undergo a course of occupational therapy, which will help improve the function of the thumb. The Occupational Therapy Program at Children’s is dedicated to collaborating with you and your child’s doctor to provide the best possible care for your child.

    Treatment programs are based on thorough evaluations and are always individualized to meet the needs of your child.

    Hand and Orthopedic Upper Extremity Program

    The Hand and Orthopedic Upper Extremity Program provides comprehensive care involving occupational and physical therapy, splinting, casting and reconstructive surgeries for infants, children and adolescents with complex congenital, neuromuscular, sports-related oncologic and traumatic upper limb conditions. 

    Boston Children's Hospital
    300 Longwood Avenue
    Fegan 2
    Boston MA 02115
     fax: 617-739-1093

    Boston Children's Hospital at Waltham
    9 Hope Avenue
    Waltham MA 02453

    Boston Children's North
    10 Centennial Drive
    Peabody MA 01960

    Hand and Reconstructive Microsurgery Program

    The specialists in the Hand and Reconstructive Microsurgery Program at Boston Children's are experts in the management of congenital and acquired hand deformities. We recognize the social elements involved in pediatric hand surgery, so an essential part of these operations has been making the child's hand as symmetrical as possible with his unaffected hand.

    Boston Children's Hospital
    300 Longwood Avenue
    Hunnewell 1
    Boston MA 02115

  • What causes an underdeveloped or absent thumb?

    Researchers still haven’t discovered the exact cause of this condition.

    How common is an underdeveloped or absent thumb?

    It’s rare, occurring in about 1 out of every 100,000 babies.

    • It can occur by itself or may be associated with other conditions where the radial side (thumb side) of the forearm does not develop properly.
    • These include Holt-Oram and Fanconi Syndromes.
    • It’s also routinely seen with radial club hand.

    In some cases, both the right and left hands may be affected.

    What symptoms might my child have?

    Because of the reduced functionality of your child’s thumb, he may have some problems with using his hand.

    What’s going to happen to happen to my child?

    Children will adapt and can function without a missing finger. Children who have no use of a thumb will learn to rely on a lateral pinch between the long and index fingers.

    However, they may have problems with fine motor activities such as pinching and grasping. It is these children who may require surgery to correct the problem.

  • How is an underdeveloped or absent thumb diagnosed?

    Thumb hypoplasia and aplasia are usually detected during your baby’s first newborn exam.

    Seeing this deformity will prompt your child's doctor to look for other deformities that are sometimes associated with this condition.

    An x-ray can help doctors examine the internal structures of your child’s thumb.

    Other tests will depend on whether the doctor believes the thumb deformity is associated with another condition.

  • How is an underdeveloped or absent thumb treated?

    Since the thumb is responsible for about half of a person's hand function, children born with underdeveloped thumbs need to be closely evaluated.

    While most surgeons recommend an operation to correct the problem in cases where your child's hand's function is impaired, your feelings and attitudes about the procedures will be taken into account.

    If there are no other pressing medical concerns that need to be addressed, surgery is generally performed when your child is between 6 and 18 months old.

    Here's a general description of treatment options that your child's doctor will discuss with you:

    • Occupational therapy— If your child has a mild case of thumb hypoplasia in which the thumb is slightly shorter or the web space between the thumb and index finger is slightly tighter than normal, surgery may not be necessary and occupational therapy is recommended.
    • Reconstruction of the thumb— This may involve one operation to accomplish the following:
    • release the tight web space between the thumb and index finger using skin grafts.
    • stabilize the middle joint through ligament reconstruction.
    • improve function and stability by transferring a tendon from another part of the hand.
    • Pollicization— This procedure is used when your child has no thumb or when the hypoplasia is more severe.


    The operation involves creating a functional thumb by transferring another finger (usually the index) to the thumb position.

    • This may seem drastic because an index finger is being sacrificed. However, since thumb function is crucial to overall hand function, having a three-fingered hand with a thumb will enable your child to have considerably better hand function than a four-fingered hand with no thumb.
    • Surgeons and parents sometimes find that a hand with one thumb and three fingers can actually be quite acceptable in appearance. This operation has an excellent track record and its results are reliable. In cases where the index finger is normal and functional, a very good thumb results.
    • The decision to undergo this procedure depends heavily on the condition of your child's index finger. If the index finger cannot move independently or has other problems, your child's doctor may not recommend pollicization.

    What's my child's long-term outlook?

    After surgery (or occupational therapy in mild cases), your child's thumb should function very well.

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