Diseases & Conditions
Upper Extremity Limb Length Discrepancy
An upper extremity limb length discrepancy is a difference in the lengths of the arms. A discrepancy can be present when a child is born (congenital) or develop when a child is older as the result of injury, infection, or disease (acquired).
Most children are able to adapt to small differences in arm length and function well without treatment. Children with large differences may need physical therapy, surgery, or other treatments to help them function better and be more independent. Because significant limb differences typically develop early on in pregnancy when a baby’s bones are being formed, some children with large differences in arm length may have other musculoskeletal problems, as well.
The bones of the arm include:
- Humerus (upper arm bone)
- Radius (the forearm bone on the “thumb side”)
- Ulna (the forearm bone on the “little finger side”)
Most long bones in the body have at least two growth plates, including one at each end. Growth plates are located between the widened part of the shaft of the bone (the metaphysis) and the end of the bone (the epiphysis). The long bones of the body do not grow from the center outward. Instead, growth occurs at each end of the bone around the growth plate. When a child is fully grown, the growth plates harden into solid bone.
Children with an upper limb length discrepancy have arms that are different lengths. A discrepancy can be present at birth (congenital) or develop when a child is older (acquired). It can affect the whole limb or just part of the limb.
Congenital Upper Limb Length Discrepancy
In a congenital upper limb length discrepancy, the arm does not form normally as a baby grows in the uterus. As a result, the baby is born with an arm that is shorter than normal or is missing.
In many cases, the cause for a congenital limb length discrepancy is not known; doctors are simply not able to determine why it has occurred.
Sometimes, a congenital limb length discrepancy is associated with a medical condition or syndrome that affects multiple parts of the body.
Congenital conditions that may cause an upper limb length discrepancy include:
- Radial deficiency. In this condition, the radius bone and soft tissues of the forearm fail to develop properly. This causes the affected hand to be bent inward toward the thumb side of the forearm, giving it the appearance of a “club hand.” The forearm may also be shortened. A radial deficiency can sometimes be associated with other congenital conditions and syndromes, including:
- Thrombocytopenia-absent radius (TAR) syndrome. A disorder characterized by low levels of platelets in the blood and absence of the radius bone in the forearm.
- Fanconi anemia. A disease that affects the body’s bone marrow and can result in skeletal abnormalities.
- Holt-Oram syndrome. A disorder in which patients have heart problems and abnormally developed bones in the upper limbs.
- VACTERL. A disorder that causes multiple anomalies including vertebral, anal, cardiac, tracheal, esophageal, renal, and limb.
- Ulnar deficiency. In this condition, the ulna bone and soft tissues of the forearm fail to develop properly, causing the wrist to bend toward the little finger side of the hand (this is the opposite direction to that seen with a radial deficiency). The severity of the condition can vary greatly from patient to patient. In the mildest cases, there may be only a mild tilt of the wrist. In the most severe cases, the ulna may be missing entirely. Patients with an ulnar deficiency sometimes have other musculoskeletal problems that affect the spine, hips, legs, and feet.
- Madelung deformity. In patients with Madelung deformity, part of the radius stops growing early, while the ulna continues to grow and dislocates, leading to malalignment of the wrist joint. Some patients with Madelung do not have noticeable symptoms and the wrist deformity is not discovered until an x-ray is taken for an unrelated reason.
Acquired Limb Length Discrepancy
An acquired limb length discrepancy is a difference in arm length that develops when a child is older. Causes may include:
- Previous injury to a bone in the arm. A broken bone in the arm can lead to a limb length discrepancy if it heals in a shortened position. This is more likely to happen if the bone was broken into many pieces. It is also more likely to happen if the injury damages the growth plate near the end of the bone—particularly at the wrist or at the shoulder. When this occurs, the bone may grow at a faster or slower rate than the bone on the opposite side.
- Bone infection. Bone infections that occur in growing children can cause an upper extremity limb length discrepancy. This is especially true if the infection happens in infancy and affects the growth plate.
- Bone diseases. Some bone diseases may result in a limb length discrepancy. Multiple hereditary exostosis (MHE) is a disorder of bone growth in which bony bumps develop close to the growth plates. When these bony bumps form on the radius or ulna, they may cause shortening or angulation of the forearm.
The effects of an upper extremity limb length discrepancy can vary greatly from one child to another, depending on the cause and size of the difference. One child may have a growth plate injury that results in just minor shortening of a bone that is hardly noticeable. Another child may have a radial deficiency that results in significant shortening of the forearm. Your doctor will talk with you to learn more about your child’s specific symptoms.
Your doctor will carefully examine your child’s arm, checking range of motion in his or her shoulder, elbow, wrist, and hand.
If your child has had an injury or infection, your doctor will want to know when it occurred and how it was treated.
If your child has a congenital condition, it will most likely have been diagnosed soon after birth. Some cases are more complex and have more than one feature, however, and referral to a specialist may be necessary to make the correct diagnosis.
X-rays. X-rays provide images of dense structures, such as bone. Your doctor will order x-rays to confirm which bone is affected and to learn more about your child’s condition. An x-ray may also be used to measure the size of a discrepancy.
Genetic testing. An evaluation by a genetic specialist may be recommended if your child has a limb length discrepancy caused by a medical condition or syndrome
Additional tests. If your doctor suspects that your child has a medical condition or syndrome, he or she may order additional testing to determine if other parts of the body are affected, such as the heart or kidneys.
If your child has a small limb length discrepancy and no functional problems, treatment is typically not needed unless symptoms develop. Children who have a significant discrepancy may need surgery to be more independent and participate in activities they are interested in.
Your doctor will consider many things when determining your child’s treatment, including:
- The cause and size of the discrepancy
- Your child’s age and overall health
- The needs of your child and the goals of the family
Nonsurgical treatment may include:
- Observation. If your child has had a fracture or infection involving the growth plate and has not yet reached skeletal maturity, your doctor may recommend simple observation until growing is complete. During this time, your child will be reevaluated at regular intervals to determine whether the discrepancy is increasing or remaining the same.
- Physical therapy. Specific exercises can help strengthen and improve range of motion in the wrist and arm.
- Occupational therapy. Exercise and training can help improve handwriting and other fine motor skills.
- Assistive or adaptive devices. Using specialized devices can make dressing and other daily activities easier.
- Prosthetics. Artificial devices can be used to replace missing parts or limbs.
There are several surgical procedures used to treat upper limb length discrepancies. The procedure your doctor recommends—as well as the age at which the procedure is performed—will depend upon the cause and size of the discrepancy, as well as the type of surgery.
Surgical procedures may involve:
- Slowing down or stopping the growth of the longer limb
- Gradual lengthening of the shorter limb with an external device or a device placed inside the bone
- Shortening of the longer limb
- Reconstruction of parts of the hand, wrist, and arm to make them appear more normal and to improve the alignment
- Skin grafts to replace skin that is missing or has been removed as part of a surgical reconstruction
How long it takes your child to recover from surgery will depend upon the specific procedure performed. During recovery, your child will have regular follow-up visits with his or her doctor and x-rays will be taken to check the healing process of the affected bone.
Physical therapy will help your child gain muscle strength and improve range of motion in the affected limb and is often required for several weeks.
If the limb length discrepancy is the result of a medical condition or syndrome, your child may have other musculoskeletal issues that require treatment, as well. Your medical team will continue to address any concerns you may have and provide the ongoing support and treatment needed to help your child thrive.
For more information about treatment for an upper extremity limb length discrepancy, please visit the Limb Lengthening and Reconstruction Society.
The Limb Lengthening and Reconstruction Society strives to maintain the highest competency in the field of musculoskeletal deficiencies and reconstruction, including limb length and extremity defects, long bone and growth deformity, limb salvage, trauma and complex limb reconstruction.
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AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS Find an Orthopaedist program on this website.