Improved Limb-Lengthening Techniques

New techniques in limb lengthening are being developed to treat leg-length discrepancy (LLD).

The basic technique of limb lengthening is standard. After applying an external fixator--a device placed outside of the leg that holds the bone in position with pins and wires--the bone is divided in a non-traumatic fashion to preserve the surrounding tissues and is gradually lengthened. As the bone lengthens, new bony tissue fills the gap.

However, several innovative ways to lengthen bones of the lower extremities have recently been introduced. These include the use of the combination of an external fixator and a metal rod inserted into the canal of the bone; the use of a telescoping nai--an expanding metal rod inserted into the internal canal of the thigh or shin bone--that is activated by leg movement; and the use of a telescoping plate, attached to the surface of the bone, gradually lengthened by frequent adjustments made by a small wrench inserted through a tiny incision in the skin.

Orthopedic experts gathered in March 2006 to discuss these and other advancements in limb lengthening and deformity correction techniques at the annual meeting of the American Academy of Orthopaedic Surgeons in Chicago (IL, USA).

Most people don't realize that if you pull bone apart slowly, it will stretch and grow, said Dr. William Mackenzie, M.D., chairman of the orthopedics department at the Alfred I. duPont Hospital for Children (Wilmington, DE, USA). However, since limbs can be lengthened only 1 mm per day, this is a very gradual process that takes a considerable amount of time.

While trauma is a common cause of LLD, many problems stem from muscle weakness, birth defects, or other deformities. LLD of up to 1 cm is common and usually treated with a shoe lift to make the legs feel the same length. But in LLD of over 2 cm, the patient usually prefers a surgical option. These include surgically shortening the longer limb or lengthening the shorter limb. While limb shortening is a less complicated and less painful procedure, there is a limit to how much the bone can shorten without causing permanent muscle weakness.



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Alfred I. DuPont Hospital for Children