True Leg Length Discrepancy Test

Overview

The two major categorizations of LLD are structural and functional. A third more minor category is environmental. In structural LLD there is an actual anatomical difference in the bones of the lower extremities where one side becomes shorter than the other. This type of LLD may be genetic, where the person is born in this way. In other cases it may be due to injury or infection through the growth phases of early childhood or adolescence. Some spinal abnormalities like scoliosis can also cause this condition. Functional LLD is where the bones are not the cause of difference but a muscle or pelvic condition has the effect of weakening the leg on one side. Conditions that can cause this are muscle inflexibility, adduction contractures and pelvic obliquity (amongst others). The third less severe category of environmental LLD is caused by discrepancies in the surface that the feet and legs are resting or walking on. Banked, uneven or curved surfaces can all cause environmental LLD. In LLD the asymmetric nature of the legs in relation to hips and back caused the centre of gravity to shift from its natural position. This then results in the body attempting to compensate by either tilting the pelvic areas towards the shorter side, increased knee flexing on the longer side, flexion of the ankle plantar and foot supination towards the shorter side.Leg Length Discrepancy

Causes

There are many causes of leg length discrepancy. Structural inequality is due to interference of normal bone growth of the lower extremity, which can occur from trauma or infection in a child. Functional inequality has many causes, including Poliomyelitis or other paralytic deformities can retard bone growth in children. Contracture of the Iliotibial band. Scoliosis or curvature of the spine. Fixed pelvic obliquity. Abduction or flexion contraction of the hip. Flexion contractures or other deformities of the knee. Foot deformities.

Symptoms

Faulty feet and ankle structure profoundly affect leg length and pelvic positioning. The most common asymmetrical foot position is the pronated foot. Sensory receptors embedded on the bottom of the foot alert the brain to the slightest weight shift. Since the brain is always trying to maintain pelvic balance, when presented with a long left leg, it attempts to adapt to the altered weight shift by dropping the left medial arch (shortening the long leg) and supinating the right arch to lengthen the short leg.1 Left unchecked, excessive foot pronation will internally rotate the left lower extremity, causing excessive strain to the lateral meniscus and medial collateral knee ligaments. Conversely, excessive supination tends to externally rotate the leg and thigh, creating opposite knee, hip and pelvic distortions.

Diagnosis

Leg length discrepancy may be diagnosed during infancy or later in childhood, depending on the cause. Conditions such as hemihypertrophy or hemiatrophy are often diagnosed following standard newborn or infant examinations by a pediatrician, or anatomical asymmetries may be noticed by a child's parents. For young children with hemihypertophy as the cause of their LLD, it is important that they receive an abdominal ultrasound of the kidneys to insure that Wilm's tumor, which can lead to hypertrophy in the leg on the same side, is not present. In older children, LLD is frequently first suspected due to the emergence of a progressive limp, warranting a referral to a pediatric orthopaedic surgeon. The standard workup for LLD is a thorough physical examination, including a series of measurements of the different portions of the lower extremities with the child in various positions, such as sitting and standing. The orthopaedic surgeon will observe the child while walking and performing other simple movements or tasks, such as stepping onto a block. In addition, a number of x-rays of the legs will be taken, so as to make a definitive diagnosis and to assist with identification of the possible etiology (cause) of LLD. Orthopaedic surgeons will compare x-rays of the two legs to the child's age, so as to assess his/her skeletal age and to obtain a baseline for the possibility of excessive growth rate as a cause. A growth chart, which compares leg length to skeletal age, is a simple but essential tool used over time to track the progress of the condition, both before and after treatment. Occasionally, a CT scan or MRI is required to further investigate suspected causes or to get more sophisticated radiological pictures of bone or soft tissue.

Non Surgical Treatment

You and your physician should discuss whether treatment is necessary. For minor LLDs in adults with no deformity, treatment may not be necessary. Because the risks may outweigh the benefits, surgical treatment to equalize leg lengths is usually not recommended if the difference is less than one inch. For these small differences, your physician may recommend a shoe lift. A lift fitted to the shoe can often improve your walking and running, as well as relieve back pain caused by LLD. Shoe lifts are inexpensive and can be removed if they are not effective. They do, however, add weight and stiffness to the shoe.

LLD Shoe Inserts

Surgical Treatment

Limb deformity or leg length problems can be treated by applying an external frame to the leg. The frame consists of metal rings which go round the limb. The rings are held onto the body by wires and metal pins which pass through the skin and are anchored into the bone. During this operation, the bone is divided. Gradual adjustment of the frame results in creation of a new bone allowing a limb to be lengthened. The procedure involves the child having an anaesthetic. The child is normally in hospital for one week. The child and family are encouraged to clean pin sites around the limb. The adjustments of the frame (distractions) are performed by the child and/or family. The child is normally encouraged to walk on the operated limb and to actively exercise the joints above and below the frame. The child is normally reviewed on a weekly basis in clinic to monitor the correction of the deformity. The frame normally remains in place for 3 months up to one year depending on the condition which is being treated. The frame is normally removed under a general anaesthetic at the end of treatment.

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