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Heel Lifts For Leg Length Discrepancy After Hip Replacement

April 27, 2015
Overview

Shortening techniques can be used after skeletal maturity to achieve leg length equality. Shortening can be done in the proximal femur using a blade plate or hip screw, in the mid-diaphysis of the femur using a closed intramedullary (IM) technique, or in the tibia. Shortening is an accurate technique and involves a much shorter convalescence than lengthening techniques. Quadriceps weakness may occur with femoral shortenings, especially if a mid-diaphyseal shortening of greater than 10% is done. If the femoral shortening is done proximally, no significant weakness should result. Tibial shortening can be done, but there may be a residual bulkiness to the leg, and risks of nonunion and compartment syndrome are higher. If a tibial shortening is done, shortening over an IM nail and prophylactic compartment release are recommended. We limit the use of shortenings to 4 to 5 cm leg length inequality in patients who are skeletally mature.Leg Length Discrepancy

Causes

There are many causes of leg length discrepancy. Some include, A broken leg bone may lead to a leg length discrepancy if it heals in a shortened position. This is more likely if the bone was broken in many pieces. It also is more likely if skin and muscle tissue around the bone were severely injured and exposed, as in an open fracture. Broken bones in children sometimes grow faster for several years after healing, causing the injured bone to become longer. A break in a child's bone through the growth center near the end of the bone may cause slower growth, resulting in a shorter leg. Bone infections that occur in children while they are growing may cause a significant leg length discrepancy. This is especially true if the infection happens in infancy. Inflammation of joints during growth may cause unequal leg length. One example is juvenile arthritis. Bone diseases may cause leg length discrepancy, as well. Examples are, Neurofibromatosis, Multiple hereditary exostoses, Ollier disease. Other causes include inflammation (arthritis) and neurologic conditions. Sometimes the cause of leg length discrepancy is unknown, particularly in cases involving underdevelopment of the inner or outer side of the leg, or partial overgrowth of one side of the body. These conditions are usually present at birth, but the leg length difference may be too small to be detected. As the child grows, the leg length discrepancy increases and becomes more noticeable. In underdevelopment, one of the two bones between the knee and the ankle is abnormally short. There also may be related foot or knee problems. Hemihypertrophy (one side too big) or hemiatrophy (one side too small) are rare leg length discrepancy conditions. In these conditions, the arm and leg on one side of the body are either longer or shorter than the arm and leg on the other side of the body. There may also be a difference between the two sides of the face. Sometimes no cause can be found. This is known as an "idiopathic" difference.

Symptoms

The effects of limb length discrepancy vary from patient to patient, depending on the cause and size of the difference. Differences of 3 1/2 percent to 4 percent of the total length of the leg (about 4 cm or 1 2/3 inches in an average adult) may cause noticeable abnormalities when walking. These differences may require the patient to exert more effort to walk. There is controversy about the effect of limb length discrepancy on back pain. Some studies show that people with a limb length discrepancy have a greater incidence of low back pain and an increased susceptibility to injuries. Other studies do not support this finding.

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

Structural leg length discrepancy can be treated with a heel lift in the shorter leg?s shoe, if the leg length is greater than 5 mm. The use and size of the heel lift is determined by a physical therapist based on how much lift is needed to restore proper lumbopelvic biomechanics. In certain cases, surgical intervention may be needed to either shorten or lengthen the limb. An important component to any surgical procedure to correct leg length discrepancies is physical therapy. Physical therapy helps to stretch muscles and maintain joint flexibility, which is essential in the healing process. For a functional leg length discrepancy no heel lift is required, but proper manual therapy techniques and specific therapeutic exercise is needed to treat and normalize pelvic and lower extremity compensations. The number of treatments needed to hold the pelvis in a symmetrical position is different for each patient based on their presentation and biomechanical dysfunctions in their lower back, pelvis, hip, knee, and foot/ankle. If you have pain in your lower back or lower extremity and possibly a length discrepancy; the two symptoms could be related. A good place to start would be a physical therapy evaluation to determine whether you have a leg length discrepancy and if it could be contributing to your lower back pain, hip pain, knee pain, or leg pain.

Leg Length

Surgical Treatment

Surgical lengthening of the shorter extremity (upper or lower) is another treatment option. The bone is lengthened by surgically applying an external fixator to the extremity in the operating room. 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 tension is created by the frame when it is "distracted" by the patient or family member who turns an affixed dial several times daily. The lengthening process begins approximately five to ten days after surgery. The bone may lengthen one millimeter per day, or approximately one inch per month. Lengthening may be slower in adults overall and in a bone that has been previously injured or undergone prior surgery. Bones in patients with potential blood vessel abnormalities (i.e., cigarette smokers) may also lengthen more slowly. The external fixator is worn until the bone is strong enough to support the patient safely, approximately three months per inch of lengthening. This may vary, however, due to factors such as age, health, smoking, participation in rehabilitation, etc. Risks of this procedure include infection at the site of wires and pins, stiffness of the adjacent joints and slight over or under correction of the bone?s length. Lengthening requires regular follow up visits to the physician?s office, meticulous hygiene of the pins and wires, diligent adjustment of the frame several times daily and rehabilitation as prescribed by your physician.

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