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    Thumb Hypoplasia | Absent Thumb

    What is thumb Hypoplasia/ Absent thumb ?

    Thumb hypoplasia/ hypoplastic thumb, means that child born with unusually small or underdeveloped thumb. Thumb aplasia means child born with complete absence of thumb.

    What are the types of thumb Hypoplasia or Aplasia ?

    In general, there are five types of thumb Hypoplasia or Aplasia:

    • Type I: Thumb is slightly smaller than normal, but all of its structures — the bones, ligaments, tendons, muscles and joints — are normal.
    • Type II: thumb is small with minor abnormalities in the tendons and muscles within the thumb.
      • Unstable joint with wobbly thumb. 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.

     thumb hypoplasia

    What causes an underdeveloped or absent thumb ?

    The exact cause of this condition not known.

    How common is an underdeveloped or absent thumb ?

    It is rare, occurs about 1 in 1 lacs childbirth.

    • It can occur alone or may be associated with other conditions where the radial side (thumb side) of the forearm does not develop properly (radial club hand).

    What problem going to happen with absent thumb ?

    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 at the time of child birth.

    An x-ray can help to provide internal structures of thumb.

    • How is an underdeveloped or absent thumb treated ?

    Since the thumb is responsible for 40% of a person’s hand function, children born with underdeveloped thumbs need to be closely evaluated.

    The surgery is generally performed in child between 1-2 year age.

    A general description of treatment options:

    • Occupational therapy— In 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:
    • Pollicization— This procedure is used when your child has no thumb or when the hypoplasia is more severe.
        • Stabilize the joint through ligament reconstruction.
        • Improve function and stability by transferring a tendon from another part of the hand.

    What is Pollicization ?

    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, quite acceptable in appearance than a four-fingered hand with no thumb.
    •  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, child may not be ideal candidate for pollicization.

     thumb hypoplasia

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

    After surgery (or occupational therapy in mild cases), thumb should function very well. With growth of child, may need some secondary corrective surgery.

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