Hemihypertrophy is a term used when one limb is growing more than the other. "Hemi" translates to half, "hyper" means above, and "trophy" is Greek for food. Those affected by hemihypertrophy often have no identifiable cause. Not only does the limb grow longer, but typically the girth is bigger as well. Hemihypertrophy is not limited to the leg. Often times, the foot, upper extremity, and even face can be affected as well.
There are syndromes that may lead to hemihypertrophy. The three most classic include:
- Klippel- Trenaunay-Weber (KTW): This is a rare medical condition in which the blood vessels and/or lymphatic vessels do not form appropriately. It is characterized by three main features including - port wine stain (nevus flammeus), malformations of the venous and lymphatic vessels, and hemihypertrophy of the soft tissue of the involved limb. Due to the increased growth and blood flow to certain limbs, major surgeries are sometimes needed to prevent the heart from working too hard. KTW is very complex, and there is not a single treatment that can apply to every child and family. Therefore, extensive discussions would occur between your COA doctor and yourself regarding treatment options.
- Beckwith–Wiedemann syndrome (BWS): In this genetic disorder, overgrowth is the rule. Its severity varies widely in children. It occurs in approximately 1:14,000 live births; boys and girls are equally affected. Some common features of BWS include large birth weight and hemihypertrophy. Blood sugars may be low during the newborn period (hypoglycemia). Not only can the limbs overgrow, but the tongue (macroglossia), and even certain abdominal organs (such as kidneys, liver, and pancreas). Since the organs can overgrow, BWS is associated with an increased risk of developing certain types of childhood cancers (most of which can be cured with proper therapies). Many children have milder cases of BWS, and therefore may never be diagnosed.
- Sturge-Weber Syndrome (SWS): This is a disorder that involves both the skin and the nervous system. It is usually characterized by a large port wine stain on the face. Children with SWS may have learning problems and developmental delays. They tend to have visual problems as well. Hemihypertrophy of the soft tissues is very common.
Initially, hemihypertrophy may be more subtle, especially when the differences in limb length and girth are not as obvious. Often times, the diagnosis is not made until your child seeks medical attention. Similar to other limb length differences, diagnosis can be made with a history and physical exam, and radiographs are particularly helpful.
Similar to other limb length inequalities, treatment is dependent on the ultimate predicted limb length difference. Most cases of hemihypertrophy result in differences at skeletal maturity between 3-6 centimeters (1.5 - 2.5 inches). To best determine the differences in limb length, your doctor may recommend visits every 6-12 months. For those differences predicted to be between 2-5 centimeters, your doctor will likely recommend to stop the growth plate on the bottom of the femur bone, top of the tibia bone (or both). The surgery is called an epiphysiodesis. Growth is stopped via a simple outpatient surgery that is minimally invasive. Through a small incision, the growth area is arrested using a drill. When the bone heals, rather than cartilage being present (as is the case with a growth area), it is replaced with bone. Once the growth area has been replaced with bone, it will no longer grow.
For differences predicted to be 5 or more centimeters, limb lengthening may be a more reasonable option. Typically, shoe lifts are worn during childhood, and then when your child is done or nearly done growing is when the limb lengthening is performed. If the limb is straight, limb lengthening with an internal lengthening nail is a great option. For a bone that is both short and crooked, correction and lengthening is likely best performed using an external fixator. Your COA surgeon will best be able to work with you and your child to help determine the best treatment plan.