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.
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.
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.
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.
Treatment Options: Surgical
In some cases, the longer extremity can be shortened with surgery. However, a major shortening may cause weakening of the muscles of the extremity. In growing children, lower extremities can also be equalized by a surgical procedure that stops growth at one or two sites of the longer extremity. It leaves the remaining growth undisturbed. Using charts or formulas, a physician calculates how much equalization can be reached by surgically stopping one or more growth centers. This procedure is performed under X-ray control. The surgeon uses a very small incision in the knee area.
The procedure will not cause immediate correction in length. Instead, the LLD gradually decreases as the opposite extremity continues to grow and "catch up." The timing of the procedure is critical; the goal is to reach equal lengths of the extremity at skeletal maturity. This usually happens by the mid- or late teens. Disadvantages include the possibility of slight over-correction or slight under-correction of the LLD. The patient's adult height will be somewhat less than if the shorter extremity had been lengthened. Correction of a significant LLD by this method may make a patient's body look disproportionate because of the shorter legs.
Surgical lengthening of the shorter arm or leg is another treatment option. The process may be immediate or gradual.
In immediate lengthening, the desired increase in the bone's length is attained while the patient is under an anesthetic in the operating room. When performing acute lengthening, the orthopaedic surgeon makes a cut in the bone, slides it and maintains the length and position with an internal device (i.e., screws or metal plates). Or the surgeon may cut the bone, spread the two sections apart, and insert a graft and internal metal devices to maintain the length. Surrounding muscles, nerves and blood vessels do not tolerate a lot of stretching. So acute lengthening can only achieve limited increases. For example, forearm bones (radius or ulna) and foot bones (metatarsals) are lengthened by this method when only a small gain in length is needed.
In gradual lengthening, the surgeon attaches a scaffold-like frame (external fixator) to the bone with metal pins, wires, or both (Figure 1). The bone is cracked through a small incision; the bone then "rests" for a few days. The patient wears the frame until the correction is achieved. The frame creates tension when it is "distracted" by the patient or family member who turns an affixed dial several times daily. The surgeon determines the rate of turning by taking X-rays every 10 to 14 days during office visits. Although this lengthening process is often called "stretching," the bone is not stretched. Instead, the very small amount of tension that the frame exerts on the bone stimulates the bone to grow. This fills the gradually enlarging gap with new bone. The surrounding muscles, nerves, skin and blood vessels also grow. The maximum rate of lengthening in children is usually 1 mm per day, or 1 inch per month. Lengthening may be slower in adults. It may also be slower in a bone that was previously injured or had surgery.
After the bone is lengthened, it must heal in the lengthened position (consolidation phase). Then the frame is removed. Under ideal conditions, the time "in the frame" is approximately 2 1/2 months to 3 months per inch. This time varies depending upon your age, general health, whether you smoke, your participation in rehabilitation, etc. Some activities may be more difficult when wearing a frame (i.e., getting in and out of a car). Most patients can easily return to work, school or daily routines. When the surgeon determines that bone strength is nearly normal again, the frame, pins, and wires are removed. Gradual lengthening can achieve significant gains in length if the process is repeated several years later, or if it is performed at opposite ends of the same bone at the same time. This "double level lengthening" achieves lengthening rates greater than 1 mm per day. Deformities, such as malunion following a broken bone, can also be corrected while the bone is being lengthened.
Many patients ask about the amount of pain associated with limb lengthening. There is some discomfort with any surgery. Pain medicine is given as needed while the patient is in the hospital (usually two days to three days). The surgeon will prescribe pain medicine as needed when you leave the hospital. Little pain is experienced once the patient is home and the lengthening process is underway. If there is a sudden increase in pain, contact your surgeon immediately. Pain may be a warning sign of a possible complication and must be addressed quickly.
As with any surgical procedure, there are risks. See your surgeon after the operation for scheduled office visits to minimize complications:
The bone may heal too rapidly (premature consolidation) and need to be cracked again to continue the lengthening process.
The bone may heal too slowly (delayed union). This can require that you wear the fixator for extra time, use an external bone stimulator or undergo more surgery, such as insertion of a bone graft.
The pins or wire sites can become infected. If untreated, infection can spread to the bone. To minimize this risk, the surgeon will tell the patient how to very carefully clean the pins and wires.
Joint stiffness (contractures) may occur during lengthening. This is especially true for significant lengthenings. If joint stiffness happens, the lengthening may need to be stopped or further surgery may be needed. Participation in prescribed physical therapy and home exercises will minimize the chances of joint problems.
Fractures of the new bone may occur when the external fixator is removed. Initially, the new bone is not as strong as the original bone. If the bone breaks, the surgeon may apply a cast, reapply the fixator or restrict the patient's physical activities.
Research on the Horizon/What's New? A new way to lengthen the bones of the lower extremities combines use of an external fixator and a metal rod inserted into the canal of the bone (intramedullary nail). This procedure is very similar to lengthening performed with an external fixator; however, it decreases the risk of newly lengthened bone bending or breaking following removal of the external fixator. The patient spends less time "in the frame" when the combined procedure is used. The main disadvantages are prolonged use of crutches or a walker and the possible risk of a severe bone infection.
Another new way to gradually lengthen limbs uses a telescoping nail. In this surgery, an expanding metal rod is inserted into the internal canal of the thighbone (femur) or shin bone (tibia) (Figure 2). Then the surgeon makes a small crack in the bone. During the next few weeks and months, the length of the nail increases. This causes lengthening of the surrounding bone. Movement of the leg activates the lengthening components of the nail. An advantage of this technique is that there is nothing worn outside the extremity.
A telescoping plate for gradual lengthening of the femur (thighbone) is currently under development. The plate is attached to the surface of the bone and a small crack is made in the bone. Beginning several days after surgery, the bone is gradually lengthened by frequent adjustments made with a small wrench through a tiny hole in the skin.
Some patients inquire about lengthening both legs to achieve greater height. This process is called cosmetic lengthening. Because of the possible complications, patient commitment and expense, cosmetic lengthening is rare. Patients who are considering cosmetic lengthening must consult an orthopaedic surgeon skilled in performing these procedures. Carefully weigh the risks and benefits of surgery.
If you have a limb length discrepancy, an orthopaedic surgeon experienced in bone lengthening techniques can explain the treatment options and their risks and benefits in more detail. You and your surgeon can then decide what treatment, if any, is best for you.