Leg length discrepancy or lower limb discrepancy (LLD) is a medical condition in which one leg is shorter than the other. The discrepancy may be in the tibia or the femur, or in both bones. If the difference in length is significant (over one 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 fast. It can also be the result of injury or a 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 one leg, especially if it affects the epiphyseal plate, or growth plate, of the tibia or femur, can also cause a discrepancy in leg lengths.
At one time, the neuromuscular disease polio was a common cause of leg length discrepancy, but the illness is now rare. Wilm’s tumor, a cancer of the kidney, is another possible cause of this condition, so it is important for children with LLD to have ultrasound examination of the kidneys in order to rule this possibility out. It is also important in the diagnosis of leg length discrepancy to rule out apparent length discrepancies in which the actual problem is a misalignment of the hips, not a difference in limb length.
For very mild LLD, under an inch (3 cm), a small heel lift in one shoe can 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 determining the length of each leg 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 an LLD patient can be stopped through a procedure called epiphyseodesis, in which the epiphyseal plate of the affected limb is removed. Epiphyseodesis is the most common surgery used to treat LLD. This method stops growth altogether and is only able to correct leg length discrepancy of two inches (5 cm) at most.
Lengthening the shorter leg is the most complicated and risky of the surgery options for LLD, but it is the best method if the discrepancy between the limbs is more than two inches. Usually, the affected bone is partially cut and an external device is used to slowly lengthen the limb, allowing gradual healing and bone growth as the leg is stretched. There is potentially no limit to how far a bone can be stretched using this method, but the longer the procedure takes, the higher the risk of complication.
Regardless of which surgery is used to treat leg length discrepancy, treatment is a lengthy process. The patient may need to be measured over a one or two year period in order to predict final leg lengths, and leg lengthening can take up to a year to complete. Luckily, many patients with LLD can be fully cured through the methods described above.