(Left) A discrepancy most often involves the femur or tibia. (Right) The location of the growth plates at the ends of the femur.
Limb length discrepancy is a difference between the lengths of the arms or legs. Except in extreme cases, differences in arm length do not usually impact how the arms function and do not require treatment. A discrepancy in leg length will usually become obvious to parents as they watch their child grow and begin to crawl and walk. Some children are born with legs of different lengths. In other cases, illness or injury causes a discrepancy in length to develop over time. While a slight difference in leg length may not cause symptoms, a significant difference can cause a noticeable limp and make it difficult for a child to run and play.
Treatment for a discrepancy depends upon the severity. Because of their complexity, limb lengthening procedures are usually reserved for patients with significant discrepancies in length.
Wooden blocks may be used to measure a discrepancy in leg length.
A broken leg bone can lead to a limb length discrepancy if it heals in a shortened position. This is more likely to happen if the bone was broken into many pieces. It is also more likely to happen if the skin and muscle tissue around the bone were severely injured and exposed, as occurs in an open fracture.
In a child, a broken bone sometimes grows faster for several years after healing, causing it to become longer than the bone on the opposite side. This type of overgrowth occurs most often in young children with femur (thighbone) fractures.
Alternatively, a break in a child's bone through the growth plate near the end of the bone may cause slower growth, resulting in a shorter leg.
Bone infections that occur in growing children may cause a significant limb length discrepancy. This is especially true if the infection happens in infancy.
Scanogram of a 13-year-old boy. The measurements at top indicate that his right leg is 30 mm (3 cm) shorter than his left leg.
Reproduced from Song K (ed): Orthopaedic Knowledge Update Pediatrics 4. Rosemont, IL. American Academy of Orthopaedic Surgeons, 2011, p. 225.
Certain bone diseases may cause limb length discrepancy, including:
Other causes of limb length discrepancy include:
Lengthening works by separating the bone and distracting (pulling apart) the bone segments very slowly so that new bone continues to form in the gap. As the bone segments are slowly distracted, the bone regenerates, resulting in increased length.
Dr. Vulcano will talk with you about your treatment options and explain the risks and benefits of limb-lengthening. Together, you and Dr. Vulcano will decide which procedure, if any, is best for your child.
X-ray of epiphysiodesis. Metal plates with screws have been placed around growth plates in both the femur and tibia to temporarily restrict growth.
Reproduced from Pierz K: Limb length discrepancy in children. Orthopaedic Knowledge Online Journal 2011; 9(6). Accessed May 2016.
(Left) In this x-ray, a section of bone has been removed to shorten the femur (arrow). A rod has been inserted to hold the bone in place during healing. (Right) After four months, the gap between the pieces of bone has healed.
Reproduced from Song K (ed): Orthopaedic Knowledge Update Pediatrics 4. Rosemont, IL. American Academy of Orthopaedic Surgeons, 2011, p. 226.
X-ray shows lengthening of a child's femur using an external fixator.