Limb Length Discrepancy
Limb length discrepancy is a difference between the lengths of the upper limbs or lower limbs.
Very rarely upper limb length discrepancies impact the function, so it usually does not require treatment. However, the lower limb length discrepancy becomes obvious to parents as they watch their child grow and begin to crawl and walk.
Most people don’t have legs of the same length, but most of the time they don’t notice.
The causes of limb length discrepancy include –
Previous injury to a bone – Fractured bone can result in limb length discrepancy if it heals in a shortened position.
Sometimes, broken bones grow faster for several years resulting in longer limb length.
If the fracture occurs through the growth plate, it will result in limb shortening due to physeal growth arrest.
Bone infection –A bone infection in a growing child may cause a significant limb length discrepancy due to physeal damage.
Bone dysplasia – Like Neurofibromatosis, Multiple hereditary exostoses, Ollier disease.
Rare causes – Idiopathic or unknown, Hemihypertrophy, Hemiatrophy
Other causes – Neurologic conditions, Juvenile arthritis.
A limb length difference may simply be a mild variation between the two sides of the body. This is usual and it is a normal variation.
The greater difference in length affects the patient’s well-being and quality of life.
Patients who have a difference of 3 to 4 percent of total leg length (about 4 cm or 1-2/3 inches) may limp or have other difficulties while walking. This is because the patients require more effort to walk and he or she will tire easily.
Young children may compensate mild to moderate leg length discrepancy by flexing the knee or walking in their toes.
On examination, the doctor will look for an identifiable cause of limb length discrepancy.
Then accurately measure the limb length, segment length, and calculate the predicted limb length discrepancy at maturity.
Scanogram is a special type of plain radiograph that uses a series of three images and a ruler to measure the length of bones.
Computerized tomography scans are indicated to know a more detailed image of bone and soft tissue of the limb.
Localized magnetic resonance imaging is indicated to study the underlying bone pathology like physeal arrest.
Non-surgical treatments are indicated for minor limb length discrepancies of less than 1 inch and have no deformity. Non-surgical treatments include either observation or wearing a shoe lift.
Surgical treatments are indicated for moderate to major limb length discrepancies and for those who have deformities. It includes either slows down/stop the growth of longer limb or shorten the longer limb or length the shorter limb.
Mild limb length discrepancy will have not any major long term consequences.
The severe limb length discrepancy will have long term morbidity, need multiple interventions and many will end up in early degeneration of the lumbar spine and lower extremity joints.