Leg Lengthening/Shortening Health Article

Definition

Leg lengthening or shortening involves a variety of surgical procedures used to correct legs of unequal lengths, a condition referred to as limb length discrepancy (LLD). LLD occurs because a leg bone grows more slowly in one leg than on the other leg. Surgical treatment is indicated for discrepancies exceeding 1 in (2.5 cm).

Purpose

Leg lengthening or shortening surgery, also known as bone lengthening, bone shortening, correction of unequal bone length, femoral lengthening, or femoral shortening, has the goal of correcting LLD and associated deformities while preserving function of muscles and joints. It is performed to:

• Lengthen an abnormally short leg (bone lengthening or femoral lengthening). Leg lengthening is usually recommended for children whose bones are skeletally immature, meaning that they are still growing. The surgery can add up to 6 in (15.2 cm) in length. The leg lengthening and deformity correction process is based on the principle of distraction osteogenesis, meaning that a bone that has been cut during surgery can be gradually distracted (pulled apart), leading to new bone formation (osteogenesis) at the site of the lengthening. The procedure basically involves breaking a bone of the leg and attaching pins through the leg into the bone. The pins pull the bones apart by about 0.4 in (1 mm) each day and the bone grows new bone to try to mend the gap. It takes about a month to grow an inch (2.5 cm).
• Shorten an abnormally long leg (bone shortening or femoral shortening). Shortening a longer leg is usually indicated for patients who have achieved skeletal maturity, meaning that their bones are no longer growing. This surgery can produce a very precise degree of correction.
• Limit the growth of a normal leg to allow a short leg to grow to a matching length (epiphysiodesis). During childhood and adolescence, the long bones—femur (thighbone) or tibia and fibula (lower leg bones)—each consist of a shaft (diaphysis) and end parts (epiphyses). The epiphyses are separated from the shaft by a layer of cartilage called the epiphyseal or growth plate. As the limbs grow during childhood and adolescence, the epiphyseal plates absorb calcium and develop into bone. By adulthood, the plates have been replaced by bone. Epiphysiodesis is an operation performed on the epiphyseal plate in one of the patient's legs that slows down the growth of a specific bone.

Leg lengthening or shortening surgery is usually recommended for severe unequal leg lengths resulting from:

• poliomyelitis, cerebral palsy, or septic arthritis
• small, weak (atrophied) muscles
• short, tight (spastic) muscles
• hip diseases, such as Legg-Perthes disease

• previous injuries or bone fractures that may have stimulated excessive bone growth
• scoliosis (abnormal spine curvature)
• birth defects of bones, joints, muscles, tendons, or ligaments

Guidelines for treatment are tailored to patient needs and are usually as follows:

• LLD < 0.79 in (2 cm): Orthotics (lift in shoe)
• LLD = 0.79-3.2 in (2-6 cm): Epiphysiodesis or shortening procedure
• LLD > 3.2 in (6 cm): Lengthening procedure
• LLD > 5.9-7.9 in (15-20 cm): Lengthening procedure, staged or combined with epiphysiodesis (Amputation is done if the procedure fails.)

Demographics

According to the Maryland Center for Limb Lengthening and Reconstruction, the rate of increase of the leg length difference is progressive in the United States with one-fourth of the LLD present at birth, one-third by age one year, and one-half by age three years in girls and four years in boys.

LLD is common in the general population, with 23% of the population having a discrepancy of 0.4 in (1 cm) or more. One person out of 1000 requires a corrective device such as a shoe lift.