The following patient information sheet is meant to help patients and family better understand a specific pediatric orthopaedic condition. It is not meant to be comprehensive, and only reflects one viewpoint. This page does not replace a medical evaluation by a pediatric orthopaedic surgeon, and your own surgeon may have a different approach to your condition.
What is leg length discrepancy?
Leg length discrepancy occurs when there is a difference in length between the two legs.
Why does my child have a leg length discrepancy?
It is very common for a person to have mild amounts of leg length discrepancy. The average person has approximately one half centimeter of discrepancy.
Larger amounts of discrepancy are generally the resulting of a separate underlying condition. Some of these conditions include previous fracture or growth plate injury, congenital femoral deficiency (the thigh bone and associated tissues are reduced), fibular or tibial hemimelia (the shin bones and associated tissues are reduced), hemihypertrophy (one side of the body is larger than the other side), or conditions where a child does not use one side of the body as much as the other (such as hemiplegic cerebral palsy).
How is the diagnosis of leg length discrepancy made?
Generally, a leg length discrepancy can be detected on physical examination. In a standing position, blocks are placed under the short leg until the pelvis is level. With the child lying down, the pelvis is squared and then the difference in length at the heels can be seen.
The exact amount of leg length discrepancy is best measured using x-rays. My preference is to obtain an image from the hips to the ankles with the child standing on blocks. An example is shown to the right. Note that one ankle appears higher in the image than the other...this is because the child is standing on a block to equalize the leg lengths. One thigh bone (femur) is significantly shorter than the other. This type of image can generally be performed on any child two years and older. Younger children generally cannot stand properly for this x-ray, and are typically imaged lying down.
When diagnosing leg length discrepancy, it is critical to determine whether there is an underlying condition associated with the discrepancy, and to determine if there are any other deformities in the bone. This requires a very careful physical examination and oftentimes a series of additional x-rays.
Will the amount of leg length discrepancy change with time?
In the growing child, most leg length discrepancies will increase as the child grows. Generally, increase in discrepancy is proportional to the growth of the child. Based on this, we can make predictions regarding how large the discrepancy will be at maturity. With repeat x-rays at regular intervals, this prediction is based on more data points and becomes more accurate. In the cases of congenital leg length discrepancy (discrepancy noted at birth), girls are half grown at 3 years and boys at 4 years, so the amount of discrepancy at these ages can be doubled to predict the ultimate discrepancy.
What amount of discrepancy requires treatment?
In general, discrepancies under two centimeters do not require treatment. Studies have suggested that people with less than two centimeters do not have any significant changes in the way they walk. Our own research is in progress, but preliminary results has suggested that less than two centimeters of discrepancy does not lead to increased arthritis in the spine, hips or knees.
Discrepancies above two centimeters do seem to make an impact. Studies have shown that discrepancies this high increase the amount of energy required to walk. People with discrepancies this high tend to report issues with their legs and back.
What treatments are available for leg length discrepancy?
The most simple treatment available is a shoe lift. I generally prescribe a lift one centimeter less than the actual discrepancy, which helps facilitate walking. Smaller lifts can be placed entirely within the shoe and are difficult to detect, while larger ones require some buildup of the bottom of the shoe. Shoe lifts can be used to treat discrepancies up to about five centimeters. Beyond this, there is a risk of ankle sprains and other issues with a large shoe lift.
In the growing child, we can take advantage of a child’s growth to equalize a leg length discrepancy. Epiphyseodesis is a procedure where a growth plate from the long side is drilled prior to maturity. This slows down growth at one particular site (the leg has four growth regions and the remaining regions continue to growth, as does the spine) and allows the legs to equalize. This is a very minor surgery. Generally it is an outpatient procedure (go home the same day), and your child is allowed to walk immediately with a brace and perhaps crutches. At about two weeks after surgery walking is usual close to normal, and at four weeks I generally allow return to sports. The most common complication is miscalculation of the amount of correction. Fortunately, the correction is generally within one centimeter of predicted amount, which should not cause any issues. As epiphyseodesis does shorten the “good” leg, we generally do not recommend corrections greater than five centimeters, which is thought to weaken the good leg due to shortening of the muscles.
In a full grown child, smaller discrepancies between two and five centimeters can be treated with acute shortening osteotomy, where the bone is shortened at the time of surgery and fixed with plate and screws or a rod. This is a more invasive surgery than epiphyseodesis. It will generally take about three months for the bone to heal, although your child may be able to walk on the leg sooner than that.
For larger predicted discrepancies, lengthening of the shorter limb is a reasonable option. This avoids the long term use of a large shoe lift, and avoids surgery on the better leg. For a fairly simple leg length discrepancy, lengthening with an implantable rod is an attractive option, although it does carry a large risk of significant complications. More commonly, there are other deformities in the leg that also need to be corrected, and thus I more often recommend lengthening with an external fixator frame. This is a large undertaking, and complications are common although in general treatable. Overall, this is a reliable way to correct all of the deformities in the leg, with a large success rate. Please see this link for more details on external fixation.