Measuring Apparent Leg Length Discrepancy

Overview

Although many of us assume our legs are the same length, it is very common for people to have one leg that is longer than the other. A leg length discrepancy (LLD) sounds alarming but people who have a discrepancy of 1cm may not even know their legs are differing lengths as often they don?t experience any problems. A Pedorthist will advise you if a leg length discrepancy or another foot or lower limb condition is the cause of your discomfort and develop a treatment plan for it.Leg Length Discrepancy

Causes

LLDs are very common. Sometimes the cause isn?t known. But the known causes of LLD in children include, injury or infection that slows growth of one leg bone. Injury to the growth plate (a soft part of a long bone that allows the bone to grow). Growth plate injury can slow bone growth in that leg. Fracture to a leg bone that causes overgrowth of the bone as it heals. A congenital (present at birth) problem (one whole side of the child?s body may be larger than the other side). Conditions that affect muscles and nerves, such as polio.

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

There are several orthopedic tests that are used, but they are rudimentary and have some degree of error. Even using a tape measure with specific anatomic landmarks has its errors. Most leg length differences can be seen with a well trained eye, but I always recommend what is called a scanagram, or a x-ray bone length study (see picture above). This test will give a precise measurement in millimeters of the length difference.

Non Surgical Treatment

Heel lifts Raise the heel on the shorter leg. It is applied either to the heel of the custom orthotic or to the inside of the shoe under the insole at the heel. Generally if the discrepancy is greater than 3/8 of an inch, the modification is applied externally on the footwear. Custom made orthotics help to provide proper support and alignment to the foot, controlling conditions such as over pronation. Orthopedic Footwear, properly fitted, to which a lift might be applied inside or out.

LLD Shoe Inserts

Surgical Treatment

The bone is lengthened by surgically applying an external fixation device to the leg. The external fixator, a scaffold-like frame, is connected to the bone with wires, pins, or both. A small crack is made in the bone and the frame creates tension when the patient or family member turns its dial. This is done several times each day. The lengthening process begins approximately five to 10 days after surgery. The bone may lengthen 1 millimeter per day, or approximately 1 inch per month. Lengthening may be slower in a bone that was previously injured. It may also be slower if the leg was operated on before. Bones in patients with potential blood vessel abnormalities, such as cigarette smokers, may also need to be lengthened more slowly. The external fixator is worn until the bone is strong enough to support the patient safely. This usually takes about three months for each inch. Factors such as age, health, smoking and participation in rehabilitation can affect the amount of time needed.

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