Leg lengthening and shortening are types of surgery to treat children who have legs of unequal lengths, usually with differences of 1 inch or more.

These procedures may:

• Lengthen an abnormally short leg
• Shorten an abnormally long leg
• Limit growth of a normal leg to allow a short leg to grow to a matching length

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.

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.

BONE GROWTH RESTRICTION

Bone growth takes place at the growth plates (physes) at each end of long bones. Restricting bone growth may be recommended for children whose bones are still growing. It is used to restrict the growth of a longer bone to allow the shorter bone to continue to grow to match its length.

While the child is under general anesthesia, the surgeons make an incision over the growth plate at the end of the bone in the longer leg.

Destroying the growth plate by scraping or drilling it (epiphysiodesis or physeal arrest) will restrict further growth at that growth plate. Proper timing of this surgical treatment is important to assure good results.

REMOVAL OF IMPLANTED METAL DEVICES

Metal pins, screws, staples, or plates may be used to stabilize bone during healing. Most orthopedic surgeons prefer to wait several months to a year before removing any large metal implants. Removal of implanted devices requires another surgical procedure using general anesthesia.

Surgical treatment may be recommended for severe unequal leg lengths caused by the following:

• Poliomyelitis and cerebral palsy
• Small, weak (atrophied) muscles or short, tight (spastic) muscles which may cause deformities and prevent normal leg growth
• Hip diseases such as Legg-Perthes disease
• Previous injuries or bone fractures that may stimulate excessive bone growth
• Birth defects (congenital deformities) of bones, joints, muscles, tendons, or ligaments

In general, leg lengthening is considered for large differences (more than 5 cm). Leg shortening or restricting is considered for smaller differences (less than 5 cm). Lengthening is also considered more often when the patient is short to begin with.

Risks for any anesthesia include:

• Reactions to medications
• Problems breathing

Risks for any surgery include:

• Bleeding
• Infection

Additional risks include:

• Bone infection (osteomyelitis)
• Injury to blood vessels
• Poor bone healing
• Nerve damage

Epiphysiodesis (bone growth restriction) is usually successful when performed at the correct time in the growth period, though it may cause an undesirable short stature.

Bone shortening may achieve more precise correction than epiphysiodesis, but requires much longer convalescence.

Bone lengthening is completely successful only 40% of the time and has a much higher rate of complications.

With bone growth restriction, hospitalization of up to a week is common. Sometimes a cast is placed on the leg for 3 - 4 weeks. Healing is complete in 8 - 12 weeks, at which time full activities can be resumed.

With bone shortening, 2 - 3 weeks of hospitalization with bedrest is usual. Sometimes a cast is placed on the leg for 3 - 4 weeks. Muscle weakness is common, and muscle-strengthening exercises are started soon after surgery. Crutches are used for 6 - 8 weeks. Some children require 6 - 12 months to regain normal knee control and function. The intramedullary (inside the bone) rod is removed at 1 year.

With bone lengthening, hospitalization lasts a week or longer. The time that the lengthening device is in use depends on the amount of lengthening to be achieved. Intensive physical therapy is required to maintain normal range of motion. Frequent visits to the doctor are necessary to adjust the lengthening device. Meticulous care of the pins holding the device is essential to prevent infection. Healing time of the bone is determined by the amount of lengthening. For each centimeter of lengthening, 36 days of healing is allotted.

Following removal of the device, activities are usually restricted for several weeks to allow for healing of the holes in the bone where the pins were. This minimizes the risk of breaking the bone through these holes until healing has occurred.

Hosalkar HS, Gholve PA, Spiegel DA. Leg-length discrepancy. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 675.