Lengthen an abnormally short leg



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送交者: heru1 于 2005-5-21, 04:06:24:


BONE LENGTHENING

Lengthening an abnormally short leg may be recommended for children whose bones are still growing. This series of treatments involves several surgical procedures, a lengthy convalescence period, and considerable risks -- but it can add up to 6 inches of length to a leg.

While the child is under general anesthesia, the bone to be lengthened is cut. Metal pins or screws are inserted through the skin and into the bone.

Pins are placed above and below the cut in the bone, and the skin incision is stitched closed.

A metal device (usually some sort of external frame) is attached to the pins in the bone and will be used later to gradually pull the cut bone apart, creating a space between the ends of the cut bone that will fill in with new bone. The lengthening device is used very gradually to ensure adequate filling of the bone and stretching of the soft tissues.

Later, when the leg has reached the desired length and has healed (usually after several months), another surgical procedure will be done to remove the pins.

Because the pins or screws are inserted through the skin into the bone, special care of the pin sites is important to prevent infection. Also, because the blood vessels, muscles, and skin are stretched with each lengthening, careful and frequent checking of the skin color, temperature, and sensation of the foot and toes is necessary to prevent circulatory, muscular, or nerve damage.

Limb lengthening is a surgical procedure used to treat a limb-length discrepancy (LLD) of the arm or leg. The goal is to achieve equal length with the corresponding opposite limb. LLD is the difference between the lengths of the upper arms and/or lower arms, or a difference between the lengths of the thighs and/or lower legs. In the past, surgeons rarely lengthened bones. That's because complications were common, the additional length gained was small, and the newly formed bone was weak. Today, advanced surgical techniques have reduced complications significantly. Patients are able to return to their daily activities soon after surgery.

LLD may be due to normal variation that occurs between the two sides of the body. Or it may be due to other causes. Some differences are so common that they are considered normal and need no treatment. For example, a study of 600 military recruits found that 32 percent had a 5 mm to 15 mm (approximately one fifth inch to three fifths inch) difference between the lengths of their two lower extremities; this is a normal variation. Greater differences may need treatment if the discrepancy affects a patient's well being and quality of life.


A physician can measure LLD during a physical examination. He or she may measure the difference between the:

Levels of the soles of the feet

Levels of each side of the pelvis when standing

Lengths from the hips to the ankles

If a more precise measurement is needed, the doctor may request an X-ray to measure the length of the bones. In growing children, a physician may repeat the physical examination and X-ray every six months to one year. This can determine if the LLD has increased or stayed the same.

Risk Factors/Prevention

There are many possible causes of LLD:


Previous injury: A previously broken bone may cause LLD if it healed in a shortened position. This can happen if the bone was broken in many pieces (comminuted) or if the skin and muscle tissue around the bone were severely injured and the bone was exposed (open fracture). In children, broken bones may grow faster for several years after healing. This causes the injured bone to become longer. A break in a child's bone through the growth center (located near the ends of the bone) can cause slower growth. This results in a shorter extremity.

Bone infection: Bone infections in growing children, especially infants, may cause significant LLD.

Bone diseases (dysplasias): These include neurofibromatosis, multiple hereditary exostoses and Ollier disease.

Inflammation: Juvenile rheumatoid arthritis is one example of inflammation of joints during growth that can cause unequal extremity length. Joint degeneration in adults (osteoarthritis) rarely causes significant LLD.

Neurological conditions: Neurological conditions during childhood, such as cerebral palsy, polio and obstetrical brachial plexus palsy, may affect the growth of an arm or leg and result in LLD.

Sometimes conditions are present at birth, but the LLD may not be detectable. As the child grows, the LLD increases and becomes more noticeable. Examples include:


Hemimelia: Underdevelopment of the inner or outer side of the leg is called hemimelia. One of the two bones between the knee and ankle (tibia or fibula) is abnormally short. There may also be foot and knee abnormalities.

Hemihypertrophy: Stimulation of growth of one side of the body from an unknown cause is called hemihypertrophy. It is a rare condition. Hemihypertrophy causes over-growth of both the arm and leg on the same side of the body. There also may be differences between the two sides of the face.

Sometimes no cause for an unequal extremity can be determined using current diagnostic methods. This is called idiopathic.

Symptoms

The effects of LLD vary from patient to patient. Symptoms depend upon the cause of the discrepancy and the size of the difference.


Differences of 3.5 percent to 4 percent of the total length of the lower extremity (4 cm or 1 2/3 inch in an average adult), including the thigh, lower leg and foot, may cause noticeable abnormalities while walking. The patient may need considerably more effort to walk.

Differences between the lengths of the upper extremities may cause few problems, unless the difference is so great that it becomes difficult to hold objects or perform chores with both hands.

A LLD may be detected on a screening examination for curvature of the spine (scoliosis). However, LLD does not cause scoliosis. There is controversy about the effect of LLD on the spine. Some studies show people with LLD have a greater incidence of low back pain and are at increased risk for injury; other studies refute this relationship.

Treatment Options

The patient and physician should discuss whether treatment is necessary. An adult with no other deformity may not need treatment for a minor LLD. Because the risks may outweigh the benefits, surgical treatment to equalize leg lengths is usually not recommended if the discrepancy is less than one inch. For small differences, the physician may recommend a shoe lift. This is fitted to the shoe. It can often improve walking and running. It can also relieve back pain caused by LLD. Shoe lifts are inexpensive. They can be removed if they are not effective. They add weight and stiffness to the shoe.

BONE SHORTENING

Shortening a longer leg may be recommended for children whose bones are no longer growing. This is a technically complicated surgery that can produce a very precise degree of correction.

While the child is under general anesthesia, the bone to be shortened is cut and a section of bone is removed. The ends of the cut bone will be joined and a metal plate with screws or a nail down the center of the bone is placed across the bone incision to hold it in place during healing.

Because the blood vessels, muscles, and skin are involved, careful and frequent checking of the skin color, temperature, and sensation of the foot and toes is necessary to prevent circulatory, muscular, or nerve damage.





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