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Plastic and Reconstructive Surgery

Hypoplastic thumb

What is a Hypoplastic Thumb?

A hypoplastic thumb is when the thumb does not develop properly or does not develop at all.

What are the Different Types of Hypoplastic Thumbs?

Hypoplastic thumbs have been grouped based on the amount of development of the thumb.

Type 1. The thumb is slightly smaller in size but function is usually like a normal thumb.

Type 2. The thumb may be slightly smaller in size. The thumb muscles are mildly underdeveloped and the thumb joint is slightly unstable. The web (skin) between the index finger and the thumb is often tight.

Type 3. The thumb may be a lot smaller in size. There is more significant loss of muscles in the thumb. The thumb joints are very unstable.

Type 4. The thumb is very small and is mostly skin and soft tissue. It may have a small bone. The thumb does not move on its own and hangs from the side of the index finger.

Level 5. No thumb.

How common is this?

Children with hypoplastic thumbs make up four percent of all congenital hand anomalies.

Why Does This Occur?

Hypoplastic thumbs may occur spontaneously or may be associated with a syndrome.

What are the Treatment Options?

Children with hypoplastic thumbs can demonstrate good use of their hand, depending on the amount of underdevelopment in the thumb. The thumb’s ability to move in the opposite direction of the other fingers (oppositional movement) is very important in the child’s ability to pick up objects of different sizes. Children with Type 1 and 2 hypoplastic thumbs may not need any surgery. Children with more hypoplastic thumbs may need surgery to stabilize the thumb joint and to create oppositional movement.

For children who are missing a thumb or can not use their thumb functionally, surgery that involves moving the index finger into the position of the thumb may be recommended. This operation is called pollicization. The children who undergo this surgery are able to pick up objects that they were not able to before surgery because of the ability to oppose with their index finger.

The Plastic Surgeon will discuss with you the best options that are most appropriate for your child.