What’s leg length discrepancy?

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Leg length discrepancy or lower extremity discrepancy (LLD) is a medical condition in which one leg is shorter than the other. The discrepancy can be in the tibia or femur or both bones. If the difference in length is significant (more than an inch or 3 cm), it can cause difficulty walking and other orthopedic problems, most commonly scoliosis.
Leg length discrepancy can be caused by congenitally underdeveloped bones in one leg or by a congenital condition that causes one side of the body to grow abnormally rapidly. It can also be the result of an injury or secondary condition. A blood vessel tumor or hemangioma in one leg can cause increased blood flow to that side, resulting in increased growth. Injury to a leg, especially if it affects the epiphyseal plate, or growth plate, of the tibia or femur, can also cause a discrepancy in leg lengths.

Neuromuscular polio was once a common cause of leg length discrepancy, but the disease is now rare. Wilm’s tumor, a cancer of the kidney, is another possible cause of this condition, so it’s important for children with LLD to have an ultrasound examination of the kidneys to rule out this possibility. It is also important in diagnosing leg length discrepancy to rule out apparent length discrepancies where the actual problem is a misalignment of the hips, not a difference in limb length.

For very mild LLD, less than one inch (3 cm), a small heel lift in a shoe may be sufficient for treatment. For more severe cases, there are three basic types of surgery used to treat leg length discrepancy: shortening the longer leg, stopping growth in the longer leg, and lengthening the shorter leg. All surgical methods require the length of each leg to be determined when growth is complete, unless the patient is already fully grown at the time of surgery. If the patient is fully grown and of a reasonable height such that losing an inch is not problematic, shortening the longer leg is the preferred course of action.

Growth in the longer leg of a patient with LLD can be stopped through a procedure called epiphysiodesis, in which the epiphyseal plate of the affected limb is removed. Epiphysiodesis is the most common surgery used to treat LLD. This method stops growth altogether and is only able to correct the leg length discrepancy of two inches (5cm) at most.

Lengthening the shorter leg is the most complicated and risky of the surgical options for LLD, but is the best method if the limb discrepancy is greater than two inches. Usually, the affected bone is partially cut and an external device is used to slowly lengthen the limb, allowing for gradual healing and bone growth as the leg is lengthened. There is potentially no limit to how much a bone can be lengthened using this method, but the longer the procedure, the higher the risk of complications.

Regardless of which surgery is used to treat the leg length discrepancy, treatment is a lengthy process. It may be necessary to measure the patient over a period of one to two years to predict final leg lengths, and leg lengthening can take up to a year to complete. Fortunately, many patients with LLD can be completely cured with the methods described above.

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