Leg Length Discrepancy After Knee Replacement Surgery

Overview

Surgeries to lengthen a leg are generally only performed when there is a difference in leg length of greater than four centimeters. These types of surgeries can be more difficult and have more complications, such as infections, delayed healing, dislocations, and high blood pressure. In a several step process, bone lengthening surgeries involve cutting a bone in two in order to allow new bone growth to occur. After the bone is cut, a special apparatus is worn with pins that will pull the bone apart at approximately one millimeter per day. This causes osteogenesis, or new bone growth, in between the cut bone segments. A cast or brace may be required for several months after surgery to allow the new bone growth to harden and provide extra support.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

Many people walk around with LLD?s of up to 2 cm. and not even know it. However, discrepancies above 2 cm. becomes more noticeable, and a slight limp is present. But even up to 3 cm. a small lift compensates very well, and many patients are quite happy with this arrangement. Beyond 3 cm. however, the limp is quite pronounced, and medical care is often sought at that point. Walking with a short leg gait is not only unsightly, but increases energy expenditure during ambulation. It could also put more stress on the long leg, and causes functional scoliosis. Where the discrepancy is more severe, walking becomes grotesque or virtually impossible.

Diagnosis

A systematic and well organized approach should be used in the diagnosis of LLD to ensure all relevant factors are considered and no clues are overlooked which could explain the difference. To determine the asymmetry a patient should be evaluated whilst standing and walking. During the process special care should be used to note the extent of pelvic shift from side to side and deviation along the plane of the front or leading leg as well as the traverse deviation of the back leg and abnormal curvature of the spine. Dynamic gait analysis should be conducted during waling where observation of movement on the sagittal, frontal and transverse planes should be noted. Also observe head, neck and shoulder movements for any tilting.

Non Surgical Treatment

In some circumstances, the physician will recommend a non-surgical form of treatment. Non-surgical treatments include orthotics and prosthetics. Orthotics are a special type of lift placed in or on a shoe that can be used in the treatment of leg length discrepancies between two and six centimeters. In pediatric patients who have large discrepancies and are not good candidates for other treatment forms, prosthetics can be helpful.

LLD Shoe Inserts

Surgical Treatment

Surgery to shorten the longer leg. This is less involved than lengthening the shorter leg. Shortening may be done in one of two ways. Closing the growth plate of the long leg 2-3 years before growth ends (around age 11-13), letting the short leg catch up. This procedure is called an epiphysiodesis. Taking some bone from the longer leg once growth is complete to even out leg lengths. Surgery to lengthen the shorter leg. This surgery is more involved than surgery to shorten a leg. During this surgery, cuts are made in the leg bone. An external metal frame and bar are attached to the leg bone. This frame and bar slowly pull on the leg bone, lengthening it. The frame and bar must be worn constantly for months to years. When the frame and bar are removed, a leg cast is required for several months. This surgery requires careful and continued follow-up with the surgeon to be sure that healing is going well.

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