Functional Leg-Length Discrepancy

Overview

leg length discrepancy can be present from birth (congenital) or acquired (a result of an injury, infection or tumor). Some of the conditions that can cause limb problems in a child or young adult include congenital conditions present from birth. Osteogenesis imperfecta,. Bow legs. Knock knees. Neurofibromatosis. Arthritis. Infections of the bones and tumors. Injuries involving the growth center of the bone. There may also be deformities that are a result of the soft tissues and not the bones, such as with arthrogryposis and burns.Leg Length Discrepancy

Causes

Leg length discrepancies can be caused by poor alignment of the pelvis or simply because one leg is structurally longer than the other. Regardless of the reason, your body wants to be symmetrical and will do its best to compensate for the length difference. The greater the leg length difference, the earlier the symptoms will present themselves to the patient. Specific diagnoses that coincide with leg length discrepancy include: scoliosis, lumbar herniated discs, sacroiliitis, pelvic obiliquity, greater trochanteric bursitis, hip arthritis, piriformis syndrome, patellofemoral syndrome and foot pronation. Other potential causes could be due to an injury (such as a fracture), bone disease, bone tumors, congenital problems (present at birth) or from a neuromuscular problem.

Symptoms

As patients develop LLD, they will naturally and even unknowingly attempt to compensate for the difference between their two legs by either bending the longer leg excessively or standing on the toes of the short leg. When walking, they are forced to step down on one side and thrust upwards on the other side, which leads to a gait pattern with an abnormal up and down motion. For many patients, especially adolescents, the appearance of their gait may be more personally troublesome than any symptoms that arise or any true functional deficiency. Over time, standing on one's toes can create a contracture at the ankle, in which the calf muscle becomes abnormally contracted, a condition that can help an LLD patient with walking, but may later require surgical repair. If substantial enough, LLD left untreated can contribute to other serious orthopaedic problems, such as degenerative arthritis, scoliosis, or lower back pain. However, with proper treatment, children with leg length discrepancy generally do quite well, without lingering functional or cosmetic deficiencies.

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

After the leg length discrepancy has been identified it can be categorized in as structural or functional and appropriate remedial action can be instigated. This may involve heel lifters or orthotics being used to level up the difference. The treatment of LLD depends on the symptoms being experienced. Where the body is naturally compensating for the LLD (and the patient is in no discomfort), further rectifying action may cause adverse effects to the biomechanical mechanism of the body causing further injury. In cases of functional asymmetry regular orthotics can be used to correct the geometry of the foot and ground contact. In structural asymmetry cases heel lifts may be used to compensate for the anatomic discrepancy.

LLD Shoe Inserts

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.

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