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Functional Leg-Length Discrepancy

Overview

Differences between the lengths of the upper and/or lower legs are called leg length discrepancies (LLD). A leg length difference may simply be a mild variation between the two sides of the body. This is not unusual in the general population. For example, one study reported that 32 percent of 600 military recruits had a 1/5 inch to a 3/5 inch difference between the lengths of their legs. This is a normal variation. Greater differences may need treatment because a significant difference can affect a patient's well-being and quality of life.Leg Length Discrepancy

Causes

The causes of LLD are many, including a previous injury, bone infection, bone diseases (dysplasias), inflammation (arthritis) and neurologic conditions. Previously broken bones may cause LLD by healing in a shortened position, especially if the bone was broken in many pieces (comminuted) or if skin and muscle tissue around the bone were severely injured and exposed (open fracture). Broken bones in children sometimes grow faster for several years after healing, causing the injured bone to become longer. Also, a break in a child?s bone through a growth center (located near the ends of the bone) may cause slower growth, resulting in a shorter extremity. Bone infections that occur in children while they are growing may cause a significant LLD, especially during infancy. Bone diseases may cause LLD, as well; examples are neurofibromatosis, multiple hereditary exostoses and Ollier disease. Inflammation of joints during growth may cause unequal extremity length. One example is juvenile rheumatoid arthritis. Osteoarthritis, the joint degeneration that occurs in adults, very rarely causes a significant LLD.

Symptoms

Often there are few or no symptoms prior to the age of 25-35. The most common symptom is chronic lower back pain, but also is frequently middle and upper back pain. Same-sided and repeated injury or pain to the hip, knee and/or ankle is also a hallmark of a long-standing untreated LLD. It is not uncommon to have buttock or radiating hip pain that is non-dermatomal (not from a disc) and tends to go away when lying down.

Diagnosis

The most accurate method to identify leg (limb) length inequality (discrepancy) is through radiography. It?s also the best way to differentiate an anatomical from a functional limb length inequality. Radiography, A single exposure of the standing subject, imaging the entire lower extremity. Limitations are an inherent inaccuracy in patients with hip or knee flexion contracture and the technique is subject to a magnification error. Computed Tomography (CT-scan), It has no greater accuracy compared to the standard radiography. The increased cost for CT-scan may not be justified, unless a contracture of the knee or hip has been identified or radiation exposure must be minimized. However, radiography has to be performed by a specialist, takes more time and is costly. It should only be used when accuracy is critical. Therefore two general clinical methods were developed for assessing LLI. Direct methods involve measuring limb length with a tape measure between 2 defined points, in stand. Two common points are the anterior iliac spine and the medial malleolus or the anterior inferior iliac spine and lateral malleolus. Be careful, however, because there is a great deal of criticism and debate surrounds the accuracy of tape measure methods. If you choose for this method, keep following topics and possible errors in mind. Always use the mean of at least 2 or 3 measures. If possible, compare measures between 2 or more clinicians. Iliac asymmetries may mask or accentuate a limb length inequality. Unilateral deviations in the long axis of the lower limb (eg. Genu varum,?) may mask or accentuate a limb length inequality. Asymmetrical position of the umbilicus. Joint contractures. Indirect methods. Palpation of bony landmarks, most commonly the iliac crests or anterior iliac spines, in stand. These methods consist in detecting if bony landmarks are at (horizontal) level or if limb length inequality is present. Palpation and visual estimation of the iliac crest (or SIAS) in combination with the use of blocks or book pages of known thickness under the shorter limb to adjust the level of the iliac crests (or SIAS) appears to be the best (most accurate and precise) clinical method to asses limb inequality. You should keep in mind that asymmetric pelvic rotations in planes other than the frontal plane may be associated with limb length inequality. A review of the literature suggest, therefore, that the greater trochanter major and as many pelvic landmarks should be palpated and compared (left trochanter with right trochanter) when the block correction method is used.

Non Surgical Treatment

Treatment for an LLD depends on the amount of difference and the cause, if known. The doctor will discuss treatment options carefully with you and your child before any decisions are made. It is important to note that treatment is planned with the child?s final height and leg lengths in mind, not the current leg lengths. Treatment is generally not needed if the child?s final LLD is predicted to be 2 centimeters or less at full height. However, the child should return to an orthopaedic doctor by age 10 for re-evaluation. Treatment is often recommended for LLDs predicted to be more than 2 centimeters at full height. If treatment is done, it usually doesn?t begin until the child starts walking. Possible treatment options include, A ?lift? in one shoe to level the child?s hips. This is often the only treatment needed for small discrepancies.

Leg Length Discrepancy Insoles

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Surgical Treatment

Surgical treatments vary in complexity. Sometimes the goal of surgery is to stop the growth of the longer limb. Other times, surgeons work to lengthen the shorter limb. Orthopedic surgeons may treat children who have limb-length conditions with one or a combination of these surgical techniques. Bone resection. An operation to remove a section of bone, evening out the limbs in teens or adults who are no longer growing. Epiphyseal stapling. An operation to slow the rate of growth of the longer limb by inserting staples into the growth plate, then removing them when the desired result is achieved. Epiphysiodesis. An operation to slow the rate of growth of the longer limb by creating a permanent bony ridge near the growth plate. Limb lengthening. A procedure (also called distraction osteogenesis or the Ilizarov procedure) that involves attaching an internal or external fixator to a limb and gradually pulling apart bone segments to grow new bone between them. There are several ways your doctor can predict the final LLD, and thus the timing of the surgery. The easiest way is the so-called Australian method, popularised by Dr. Malcolm Menelaus, an Australian orthopedic surgeon. According to this method, growth in girls is estimated to stop at age 14, and in boys at age 16 years. The femur grows at the rate of 10 mm. a year, and the upper tibia at the rate of 6 mm. a year. Using simple arithmetic, one can get a fairly good prediction of future growth. This of course, is an average, and the patient may be an average. To cut down the risk of this, the doctor usually measures leg length using special X-ray technique (called a Scanogram) on three occasions over at least one year duration to estimate growth per year. He may also do an X-ray of the left hand to estimate the bone age (which in some cases may differ from chronological age) by comparing it with an atlas of bone age. In most cases, however, the bone age and chronological age are quite close. Another method of predicting final LLD is by using Anderson and Green?s remaining growth charts. This is a very cumbersome method, but was till the 1970?s, the only method of predicting remaining growth. More recently, however, a much more convenient method of predicting LLD was discovered by Dr. Colin Moseley from Montreal. His technique of using straight line graphs to plot growth of leg lengths is now the most widely used method of predicting leg length discrepancy. Whatever method your doctor uses, over a period of one or two years, once he has a good idea of the final LLD, he can then formulate a plan to equalize leg lengths. Epiphyseodesis is usually done in the last 2 to 3 years of growth, giving a maximum correction of about 5 cm. Leg lengthening can be done at any age, and can give corrections of 5 to10 cm., or more.
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