How To Gauge Apparent Leg Length Discrepancy

Overview

Your child has been diagnosed with a leg-length discrepancy. This means that your child?s legs are slightly different lengths, with one leg longer than the other. The difference in lengths can vary widely. The larger the difference in lengths, the more problems that can result as the child gets older. Because of this, your child may be referred to a pediatric orthopedist (doctor specializing in treating bone and joint problems in children) for evaluation and possible treatment.

Causes

Some causes of leg length discrepancy (other than anatomical). Dysfunction of the hip joint itself leading to compensatory alterations by the joint and muscles that impact on the joint. Muscle mass itself, i.e., the vastus lateralis muscle, pushes the iliotibial band laterally, causing femoral compensations to maintain a line of progression during the gait cycle. This is often misdiagnosed as I-T band syndrome and subsequently treated incorrectly. The internal rotators of the lower limb are being chronically short or in a state of contracture. According to Cunningham's Manual of Practical Anatomy these are muscles whose insertion is lateral to the long axis of the femur. The external rotators of the hip joint are evidenced in the hip rotation test. The iliosacral joint displays joint fixations on the superior or inferior transverse, or the sagittal axes. This may result from many causes including joint, muscle, osseous or compensatory considerations. Short hamstring muscles, i.e., the long head of the biceps femoris muscle. In the closed kinetic chain an inability of the fibula to drop inferior will result in sacrotuberous ligament loading failure. The sacroiliac joint dysfunctions along its right or left oblique axis. Failure or incorrect loading of the Back Force Transmission System (the longitudinal-muscle-tendon-fascia sling and the oblique dorsal muscle-fascia-tendon sling). See the proceedings of the first and second Interdisciplinary World Congress on Low Back Pain. Sacral dysfunction (nutation or counternutation) on the respiratory axis. When we consider the above mentioned, and other causes, it should be obvious that unless we look at all of the causes of leg length discrepancy/asymmetry then we will most assuredly reach a diagnosis based on historical dogma or ritual rather than applying the rules of current differential diagnosis.

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

The only way to decipher between anatomical and functional leg length inequalities (you can have both) is by a physical measurement and series of biomechanical tests. It is actually a simple process and gets to the true cause of some runner?s chronic foot, knee, hip and back pain. After the muscles are tested and the legs are measured it may be necessary to get a special X-ray that measures both of your thighs (Femurs) and legs (Tibias). The X-ray is read by a medical radiologist who provides a report of the actual difference down to the micrometer leaving zero room for error. Once the difference in leg length is known, the solution becomes clear.

Non Surgical Treatment

A personalized approach to leg length discrepancy treatment works best for each patient. Your child's doctor will consider many factors when deciding on a course of treatment for this condition. Such factors can include your child's age, extent of the leg length discrepancy, medical history, how your child tolerates certain treatments and procedures, your child's health and prognosis, growth rate, and parental preferences. There is no cookie cutter treatment for each child, or even each centimeter of leg difference. Once all of these factors have been carefully considered, your child's physician will come up with an appropriate course of care. In situations of a very small leg length discrepancy, no treatment, only periodic medical evaluation, may be necessary.



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Surgical Treatment

Surgical operations to equalize leg lengths include the following. Shortening the longer leg. This is usually done if growth is already complete, and the patient is tall enough that losing an inch is not a problem. Slowing or stopping the growth of the longer leg. Growth of the lower limbs take place mainly in the epiphyseal plates (growth plates) of the lower femur and upper tibia and fibula. Stapling the growth plates in a child for a few years theoretically will stop growth for the period, and when the staples were removed, growth was supposed to resume. This procedure was quite popular till it was found that the amount of growth retarded was not certain, and when the staples where removed, the bone failed to resume its growth. Hence epiphyseal stapling has now been abandoned for the more reliable Epiphyseodesis. By use of modern fluoroscopic equipment, the surgeon can visualize the growth plate, and by making small incisions and using multiple drillings, the growth plate of the lower femur and/or upper tibia and fibula can be ablated. Since growth is stopped permanently by this procedure, the timing of the operation is crucial. This is probably the most commonly done procedure for correcting leg length discrepancy. But there is one limitation. The maximum amount of discrepancy that can be corrected by Epiphyseodesis is 5 cm. Lengthening the short leg. Various procedures have been done over the years to effect this result. External fixation devices are usually needed to hold the bone that is being lengthened. In the past, the bone to be lengthened was cut, and using the external fixation device, the leg was stretched out gradually over weeks. A gap in the bone was thus created, and a second operation was needed to place a bone block in the gap for stability and induce healing as a graft. More recently, a new technique called callotasis is being use. The bone to be lengthened is not cut completely, only partially and called a corticotomy. The bone is then distracted over an external device (usually an Ilizarov or Orthofix apparatus) very slowly so that bone healing is proceeding as the lengthening is being done. This avoids the need for a second procedure to insert bone graft. The procedure involved in leg lengthening is complicated, and fraught with risks. Theoretically, there is no limit to how much lengthening one can obtain, although the more ambitious one is, the higher the complication rate.