Similar, but opposite of hemihypertrophy, "hemiatrophy" is a term used when one limb is growing less than the other. "Hemi" translates to half, "a" translates to "without" and "trophy" means food. Not only is the limb shorter, but typically the girth is narrower as well.
Those affected by hemiatrophy often have an identifiable cause. The most classic example of hemiatrophy is hemiplegic cerebral palsy. In this condition, half of the body is neurologically weaker compared to the other side. As a result of half the body having less neurologic input, growth of the bones and muscles on that side are affected as well and it becomes smaller. Another common cause of hemiatrophy is an isolated clubfoot. Those who have a clubfoot on one side not only have a smaller foot, but the leg itself is thinner and shorter.
Initially, hemiatrophy may be 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 hemiatrophy rarely result in differences that need to be treated. 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, which are extremely rare, limb lengthening may not be an option. Limbs that are neurologically impaired are often not safe for lengthening due to increased risk of muscle contractures and/or joint dislocations. Ultimately the decision on how to treat this large of a difference will require careful planning between you, your child, and your COA doctor.