Arm or Leg Length Discrepancies

Differences between the lengths of the upper and/or lower arms and the upper and/or lower legs are called limb length discrepancies (LLD). Except in extreme cases, arm length differences (congenital hand deformities) cause little or no problem in how the arms function. Therefore, the main focus is mostly on differences in the leg length.

Symptoms of limb deformities

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 short leg syndrome (noticeable abnormalities when walking). These differences may require the patient to exert more effort to walk.

Causes of leg length discrepancy

• Previous Injury to a Bone in the Leg: A broken leg bone may lead to a limb 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.
• Bone Infection: Bone infections that occur in children while they are growing may cause a significant limb length discrepancy. This is especially true if the infection happens in infancy. Inflammation of joints during growth may cause uneven leg length. One example is juvenile arthritis.
• Bone Diseases (Dysplasias): They may also cause limb length discrepancies. Examples are: Neurofibromatosis, Multiple hereditary exostoses and Ollier disease
• Other Causes: Other causes include inflammation (arthritis) and neurologic conditions

Treatment

Nonsurgical Treatment: For minor limb length discrepancy in patients with no deformity, treatment may not be necessary. Because the risks may outweigh the benefits, surgical treatment to equalize leg lengths is usually not recommended if the difference is less than 1 inch. For these small differences, the physician may recommend a shoe lift. A lift fitted to the shoe can often improve walking and running, as well as relieve any back pain that may be caused by the limb length discrepancy. Shoe lifts are inexpensive and can be removed if they are not effective.

Surgical Treatment: Surgery may involve either leg shortening or leg lengthening procedures. In some cases the longer leg can be shortened, but a major shortening may weaken the muscles of the leg. In the thighbone (femur), a maximum of 3 inches can be shortened. In the shinbone, a maximum of 2 inches can be shortened.
Surgical lengthening of the shorter leg is another choice. The bone is lengthened by surgically applying an external fixation device to the leg. 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 the frame creates tension when the patient or family member turns its dial. This is done several times each day. The lengthening process begins approximately five to 10 days after surgery. The bone may lengthen 1 millimeter per day, or approximately 1 inch per month.
The external fixator is worn until the bone is strong enough to support the patient safely. This usually takes about three months for each inch. Factors such as age, health, smoking and participation in rehabilitation can affect the amount of time needed.

Risks of this procedure include:

• Infection at the site of wires and pins
• Stiffness of the adjacent joints
• Slight over- or under-correction of the bone's length

Leg lengthening procedure requires:

• Regular follow-up visits to the physician's office
• Meticulous cleaning of the area around the pins and wires
• Diligent adjustment of the frame several times daily
• Rehabilitation as prescribed by the physician