Hypoplastic Thumb

Thumbs are essential for everyday hand movements, like gripping, pinching and picking up small objects. When a child is born with an underdeveloped or missing thumb - a condition called hypoplastic thumb - it can affect how they perform everyday tasks.

At Banner Children’s, we provide expert care for children with congenital hand differences, such as hypoplastic thumbs. Our team provides personalized treatment and long-term support to help your child build strength, function and confidence.

What is hypoplastic thumb?

Hypoplastic thumb, or thumb hypoplasia, is a congenital hand difference where a baby is born with an underdeveloped thumb or no thumb at all. The condition can range from mild to severe. The thumb may be slightly smaller or completely missing (thumb aplasia).

Because the thumb plays an important role in grip and pinch movements, children with hypoplastic thumb may have difficulty holding objects or performing fine motor skills. This condition can affect just one hand, but over half of the cases involve both hands.

Types of hypoplastic thumb

There are five main types of hypoplastic thumb. The type your child has depends on how developed the thumb is and how well it works. 

• Type I: The thumb is slightly smaller but still works well. Children with this type of hypoplastic thumb may not need surgery. 
• Type II: The thumb is small and weak. The muscles and joints may not work properly, making it hard to pinch and grip. Thumb reconstruction surgery can help improve strength and movement.
• Type III: The thumb is smaller and more unstable. The bones, muscles and ligaments may be missing or not formed correctly. Surgery is often needed to rebuild or replace the thumb.
  • Type IIIA: The base of the thumb (carpometacarpal joint) is stable but the muscles and tendons are weak.
  • Type IIIB: The base of the thumb is unstable. The joint connects the thumb to the wrist and helps it move. In this type, the joints, muscles and tendons are poorly formed and the thumb may not be functional.
• Type IV: The thumb is only connected to the hand by skin and soft tissue. It lacks the bones and support needed to function. It usually can’t be used and is often removed and replaced with a finger to act as a new thumb (pollicization).
• Type V: The thumb is completely missing. Pollicization is usually recommended so the hand can still pinch and grip.

Each child is different. A pediatric hand specialist or pediatric orthopedic surgeon will examine your child’s thumb and decide on the best treatment to help them use their hand as well as possible. 

What causes hypoplastic thumb?

Hypoplastic thumb develops during early pregnancy, often without a known cause. It usually happens by chance and is not caused by anything you did or didn’t do.

Sometimes, hypoplastic thumb is part of a larger condition that affects other parts of the body. These may include:

• Holt-Oram syndrome (hand-heart syndrome): A condition that affects the heart and upper limbs.
• Radial club hand: A condition where the bones on the thumb side of the forearm (radius) don’t form properly.
• VACTERL association: A group of birth differences that may affect the spine, heart, kidneys, arms and other areas.
• Fanconi anemia: A rare blood disorder that can lead to bone problems and other health issues.

Your child’s health care provider may recommend genetic testing or other tests for related conditions.

Symptoms of hypoplastic thumb

Children with hypoplastic thumb may show signs at birth or as they begin to use their hands. 

Signs may include:

• A small or weak thumb
• Poor thumb movement
• Trouble with pinching or grasping
• A tight web space between the thumb and index finger
• A floppy or unstable thumb
• Weak grip or hand strength
• The thumb may appear normal on the outside but lack internal bone or ligament support.
• Missing thumb entirely 

How hypoplastic thumb is diagnosed

Hypoplastic thumb is usually diagnosed shortly after birth during a newborn exam. Your child’s health care provider will perform a physical exam to check the thumb’s size, strength and movement. They may also order imaging tests like X-rays to look at bones and joints.

Your child may be referred to a pediatric hand specialist or orthopedic surgeon for further evaluation and treatment.

Treatments for hypoplastic thumb

Treatment depends on how developed the thumb is and how well it works. The main goal is to improve how the hand functions.

Non-surgical treatments

Mild cases (such as Type I) may not need surgery. Your child may benefit from:

• Occupational therapy: For mild cases, an occupational therapist can help your child build thumb strength and movement. If surgery is needed, therapy supports recovery and maximizes results.
• Follow-up visits: Your child will regularly see their health care team to track hand growth and function.

Surgical treatments

Surgery is often needed for moderate to severe types (Types II through V). There are two main procedures:

Thumb reconstruction

Thumb reconstruction is used for Type II or IIIA thumbs. It improves strength, movement and joint stability by repairing or rebuilding muscles, tendons or bones.

• Typically performed between 6 and 18 months of age
• Done as an outpatient procedure (your child goes home the same day)
• Recovery includes a cast followed by a splint
• Several months of pediatric hand therapy are needed for best results

Pollicization

Pollicization is often used for Type IIIB, IV or V thumbs. In this procedure, the index finger is moved and reshaped to act like a thumb - restoring pinch and grip ability.

• Usually performed as an inpatient procedure (your child stays overnight)
• Recovery involves a cast followed by a splint
• Hand therapy is needed after surgery to regain strength and function
• Additional procedures may improve finger spacing or motion

What is the outlook for hypoplastic thumb?

Many children with hypoplastic thumb go on to lead active, independent lives. Outcomes depend on how severe the condition is and the type of treatment your child receives.

Children with mild cases often do well with therapy alone. Those with more severe types who have surgery can gain strong, useful hand function. These treatments can help your child with everyday activities like writing, feeding, dressing and playing.

Your child’s hand may continue to grow and change, so ongoing therapy and checkups can help make sure they stay on track. Most children adjust well and learn new ways to use their hands with support from their family and care team.

Why choose Banner Children’s

At Banner Children’s, we care for children with all types of congenital hand differences, including hypoplastic thumb. Our team includes pediatric hand specialists and orthopedic surgeons, trained in advanced treatments like thumb reconstruction and pollicization. 

We offer:

• Pediatric hand specialists skilled in thumb reconstruction and pollicization
• Personalized treatment plans based on your child’s needs
• Therapy and support services to build strength and function
• Expert care for related conditions like radial dysplasia
• Long-term follow-up as your child grows

Make an appointment

If your child was born with an underdeveloped or missing thumb, early diagnosis and treatment can make a big difference.

Schedule an appointment with a Banner Children’s specialist today.

We’re here to answer your questions, support your family and help your child thrive.