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Leg Length Discrepancy (Pediatric)

What is leg length discrepancy?

Leg length discrepancy (LLD) is an orthopedic problem that usually appears in childhood, in which a child’s two legs are of unequal lengths. A leg length discrepancy may be caused by or associated with a number of other orthopedic or medical conditions, but is generally treated in a similar way, regardless of cause and depending on severity.  

What causes leg length discrepancy?

There are many causes for a leg length discrepancy and can be divided into 3 categories: those that cause a limb to shorten, those that cause it to lengthen and those that are caused by an issue above the legs such as a tilt in the pelvis. 

Causes that shorten the leg are more common than those that lengthen it and include congenital growth deficiencies such as genetic conditions affecting growth, infections that affect the growth plate, tumors, fractures that occur through the growth plate, and radiation treatment for cancer.   

Lengthening can result from rare conditions such as when one side of the body is larger than the other side, vascular malformations or tumors such as hemangiomas, Wilm's tumor (of the kidney), septic arthritis, healed fractures, or other orthopedic surgeries.

If a child has a tilt in their pelvis or another issue within the spine that may cause the leg to appear to be shorter or longer on one side it is considered a functional LLD and not a “true” LLD.

How is leg length discrepancy diagnosed?

Leg length discrepancy may be diagnosed as an infant or later in childhood, depending on the cause.   

In older children, LLD is frequently first suspected by a parent or pediatrician because of a limp that appears to be getting worse. The standard workup for LLD is a thorough physical examination, including watching the child walk and run as well as a 3-joint standing x-ray or an x-ray scanogram to determine the actual length of the bones of the legs.

The orthopedic surgeon uses the measurements from the imaging to determine how big the discrepancy will be when the child is done growing and this helps determine the best treatment plan for the child.

How is leg length discrepancy treated?

The treatment of LLD depends on the cause, the age of the patient, and the severity of the discrepancy.   Non-operative treatment is usually the first step in management and, in many cases; LLD is mild or is predicted to lessen in the future, based on growth rate estimates.   In such cases, no treatment may be necessary or can be delayed until a later stage of physical growth that allows for a better predictive estimate.  

For children with a small discrepancy (less than 2 cm) a lift placed into the shoe can be an adequate treatment while some children with the same discrepancy may choose no treatment at all. 

For children with a predicted LLD of 2.5 cm or more a surgical operation is the best treatment for LLD.   Surgeries for leg length discrepancy are designed to do one of three general things: 

  1. shorten the long leg
  2. stop or slow the growth of the longer 
  3. more rapidly growing leg or lengthen the short leg

Stopping or slowing the growth of the longer leg is the most commonly used of the three approaches and incorporates an operation known as a growth modulation, in which the growth plate of either the lower femur or upper tibia (or both) are either fastened temporarily using small metal plates or it is drilled to stop the growth. The operation usually is planned for the last 2 to 3 years of growth and has excellent results. However, it is only appropriate for LLD of less than 3-4 cm.

Leg lengthening is an option that is used for LLD more than 4 cm. An external fixator is placed in the operating room and a cut is placed through the bone (either tibia or femur). The fixator is then used to gradually lengthen the affected leg. This process takes several months including the time needed for the new bone to form in the space made from lengthening.  Unlike the growth modulation, leg lengthening procedures can be performed at almost any age. 

Leg shortening is used when a LLD is severe and when a patient has already reached the end of growth.   The surgery is called an osteotomy, which includes the removal of a small section of bone in the tibia (shinbone) or femur (thigh bone) and placement of a metal plate. This would result in the child being as tall as their shortest side.

If large enough, a LLD left untreated can contribute to other serious orthopedic problems, such as scoliosis, arthritis, or lower back pain.  

However, with proper treatment, children with leg length discrepancy often do quite well, without lasting functional or cosmetic deficiencies and can participate in sports and other demanding activities.