Limb-Length Discrepancy After Hip Arthroplasty

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Overview

People with leg length discrepancy, when one leg is longer than the other, usually have a waddling-type gait where the hips seem to move up and down during walking as the body tries to compensate for the inequality. There are two types of leg length discrepancy. The first type of leg length discrepancy involves a structural defect, where one bone is longer or shorter than the corresponding bone of the other limb. This can occur within the femur (upper leg bone) or the tibia and fibular (lower leg bones). Functional leg length discrepancy results from altered mechanics due to a malalignment in the spine or lower extremity.Leg Length Discrepancy

Causes

Some limb-length differences are caused by actual anatomic differences from one side to the other (referred to as structural causes). The femur is longer (or shorter) or the cartilage between the femur and tibia is thicker (or thinner) on one side. There could be actual deformities in one femur or hip joint contributing to leg length differences from side to side. Even a small structural difference can amount to significant changes in the anatomy of the limb. A past history of leg fracture, developmental hip dysplasia, slipped capital femoral epiphysis (SCFE), short neck of the femur, or coxa vara can also lead to placement of the femoral head in the hip socket that is offset. The end-result can be a limb-length difference and early degenerative arthritis of the hip.

Symptoms

The symptoms of limb deformity can range from a mild difference in the appearance of a leg or arm to major loss of function of the use of an extremity. For instance, you may notice that your child has a significant limp. If there is deformity in the extremity, the patient may develop arthritis as he or she gets older, especially if the lower extremities are involved. Patients often present due to the appearance of the extremity (it looks different from the other side).

Diagnosis

Infants, children or adolescents suspected of having a limb-length condition should receive an evaluation at the first sign of difficulty in using their arms or legs. In many cases, signs are subtle and only noticeable in certain situations, such as when buying clothing or playing sports. Proper initial assessments by qualified pediatric orthopedic providers can reduce the likelihood of long-term complications and increase the likelihood that less invasive management will be effective. In most cases, very mild limb length discrepancies require no formal treatment at all.

Non Surgical Treatment

Internal heel lifts: Putting a simple heel lift inside the shoe or onto a foot orthotic has the advantage of being transferable to many pairs of shoes. It is also aesthetically more pleasing as the lift remains hidden from view. However, there is a limit as to how high the lift can be before affecting shoe fit. Dress shoes will usually only accommodate small lifts (1/8"1/4") before the heel starts to piston out of the shoe. Sneakers and workboots may allow higher lifts, e.g., up to 1/2", before heel slippage problems arise. External heel lifts: If a lift of greater than 1/2" is required, you should consider adding to the outsole of the shoe. In this way, the shoe fit remains good. Although some patients may worry about the cosmetics of the shoe, it does ensure better overall function. Nowadays with the development of synthetic foams and crepes, such lifts do not have to be as heavy as the cork buildups of the past. External buildups are not transferable and they will wear down over time, so the patient will need to be vigilant in having them repaired. On ladies' high-heel shoes, it may be possible to lower one heel and thereby correct the imbalance.

Leg Length

Surgical Treatment

Surgical options in leg length discrepancy treatment include procedures to lengthen the shorter leg, or shorten the longer leg. Your child's physician will choose the safest and most effective method based on the aforementioned factors. No matter the surgical procedure performed, physical therapy will be required after surgery in order to stretch muscles and help support the flexibility of the surrounding joints. Surgical shortening is safer than surgical lengthening and has fewer complications. Surgical procedures to shorten one leg include removing part of a bone, called a bone resection. They can also include epiphysiodesis or epiphyseal stapling, where the growth plate in a bone is tethered or stapled. This slows the rate of growth in the surgical leg.
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