Limb Length Differences

Lower extremity growth disorders

  • Limb length discrepancy is a difference in the length of one leg as compared to the other leg. Most people have a little difference between the leg lengths and it is not noticeable. Bigger differences can be caused by a fracture that affected the growth of the leg, a bone infection that affected normal growth, or other diseases that caused bone deformities.
  • Genu valgum (knock knees) - Most children develop knock knees around age 3 and grow out of it by age 8-9 without any need for treatment. Knock knees in either one or both legs can be caused by other bone diseases or growth problems.
  • Blount's disease is a condition that affects the growth plate below the knee and causes the tibia to bow.
  • Rickets is a bone disease that causes bowed legs and other bone deformities. It is caused by lack of calcium, phosphorus and vitamin D. It can be caused by a genetic disorder which makes it hard for the body to absorb vitamin D and can be treated with medication.
  • Rotational deformities of the legs can cause too much turning in or turning out of the thigh (femur) or shin (tibia) bones. Usually children outgrow these as well without need for treatment.

 

Symptoms

In addition to the bone deformities, some children can develop hip, knee or ankle pain if any of these deformities cause a big change in the alignment of the legs. Sometimes they will limp or have problems with walking or running.

 

Evaluation

  • X-rays will be done to check the alignment of the legs and any bone deformities.
    • Scanograms are special x-rays that measure the length of the long bones and are used to measure a leg length difference. An x-ray of the wrist can be done to determine how mature the bones are to find out how much growth is left.
  • CT scan can be done to find out how much rotation of the long bones is present.
  • Blood test can determine if the child has rickets or other metabolic disorders causing the bone deformities.

Guided Growth Surgery

A variety of surgical techniques can be done to correct many of these growth abnormalities.
For a small difference in length, the growth of the longer leg can be slowed to allow the shorter leg to catch up. A bowed leg can be corrected by having a small plate placed internally on part of the growth plate to guide the leg to grow in a corrected position. Bigger differences in length or bowing can be corrected with the use of an external device attached to the leg during surgery. Daily adjustments of the device at home will gradually correct the deformity. The device is removed when the alignment has improved and the bone has healed. Severe rotational deformities can be corrected by surgically cutting and rotating the femur or tibia.