Thumb Hypoplasia

What is Thumb Hypoplasia? Thumb Hypoplasia means that your child’s thumb is unusually small or under-developed. Severity ranges from a thumb that is slightly smaller with normal structures through varying degrees of bone, tendon, ligament, muscle and joint under-development, to complete absence of the thumb.

What causes an underdeveloped or absent thumb? The exact cause of the condition remains unknown.

How common is an under-developed 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 such as radial club hand in which the inner (radial) aspect of the forearm, wrist and hand do not develop properly. It can be associated with medical conditions such as Holt-Oram Syndrome and Fanconi’s Anaemia.

How is an under-developed or absent thumb diagnosed? Thumb Hypoplasia and Aplasia are usually detected during your baby’s first newborn examination. X-rays are used to examine how the underlying bones are affected. In addition your baby may be evaluated for other problems that are sometimes associated with this condition. Other scans and tests may be required in this regard.

How is an under-developed or absent thumb treated? Treatment is always discussed and planned to meet the needs of your child. 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.

There are a variety of different options that can be used:

Physiotherapy – If your child has a mild case of Thumb Hypoplasia surgery may not be necessary and physiotherapy with a specialist hand therapist is recommended.

Reconstruction of the thumb – This involves surgery to release the tight web space between the thumb and index finger. This may require the use of skin grafts. In addition, as part of the procedure, the middle thumb joint may need to be stabilized and a tendon transfer may be carried from another part of the hand to improve function and stability.

Pollicisation – This procedure is used when your child has a severely under-developed thumb or no thumb at all. The operation involves creating a functional thumb by transferring another finger (usually the index) to the thumb position. This operation has an excellent track record and its results are reliable.

Decisions regarding treatment are made very carefully and are always aimed at improving your child’s overall hand function.

What’s my child’s long-term outlook? After surgery (or physiotherapy in mild cases), your child’s thumb should function very well. Long-term follow-up is required to ensure that healing is going well and function is optimised. Your surgical team may see your child to help reduce scarring, swelling and stiffness and improve strength.  Your child will continue to be followed-up as they grow to ensure that they are adapting and functioning well.

Contact Reach charity for more information and support