Overview
The field of leg length inequalities or leg length discrepancy often abbreviated as LLD is well documented and understood. There are two types of short legs; functional (functional LLD) and structural (true LLD). A functional short leg occurs as a result of muscle imbalances, pelvic torsion or other mechanical reasons. The millimeters of ?appearing? short are typically less than 10, and are do not appear on Xray. This article is about structural or anatomical short legs.
Causes
Some children are born with absence or underdeveloped bones in the lower limbs e.g., congenital hemimelia. Others have a condition called hemihypertrophy that causes one side of the body to grow faster than the other. Sometimes, increased blood flow to one limb (as in a hemangioma or blood vessel tumor) stimulates growth to the limb. In other cases, injury or infection involving the epiphyseal plate (growth plate) of the femur or tibia inhibits or stops altogether the growth of the bone. Fractures healing in an overlapped position, even if the epiphyseal plate is not involved, can also cause limb length discrepancy. Neuromuscular problems like polio can also cause profound discrepancies, but thankfully, uncommon. Lastly, Wilms? tumor of the kidney in a child can cause hypertrophy of the lower limb on the same side. It is therefore important in a young child with hemihypertrophy to have an abdominal ultrasound exam done to rule out Wilms? tumor. It is important to distinguish true leg length discrepancy from apparent leg length discrepancy. Apparent discrepancy is due to an instability of the hip, that allows the proximal femur to migrate proximally, or due to an adduction or abduction contracture of the hip that causes pelvic obliquity, so that one hip is higher than the other. When the patient stands, it gives the impression of leg length discrepancy, when the problem is actually in the hip.
Symptoms
Faulty feet and ankle structure profoundly affect leg length and pelvic positioning. The most common asymmetrical foot position is the pronated foot. Sensory receptors embedded on the bottom of the foot alert the brain to the slightest weight shift. Since the brain is always trying to maintain pelvic balance, when presented with a long left leg, it attempts to adapt to the altered weight shift by dropping the left medial arch (shortening the long leg) and supinating the right arch to lengthen the short leg.1 Left unchecked, excessive foot pronation will internally rotate the left lower extremity, causing excessive strain to the lateral meniscus and medial collateral knee ligaments. Conversely, excessive supination tends to externally rotate the leg and thigh, creating opposite knee, hip and pelvic distortions.
Diagnosis
The only way to decipher between anatomical and functional leg length inequalities (you can have both) is by a physical measurement and series of biomechanical tests. It is actually a simple process and gets to the true cause of some runner?s chronic foot, knee, hip and back pain. After the muscles are tested and the legs are measured it may be necessary to get a special X-ray that measures both of your thighs (Femurs) and legs (Tibias). The X-ray is read by a medical radiologist who provides a report of the actual difference down to the micrometer leaving zero room for error. Once the difference in leg length is known, the solution becomes clear.
Non Surgical Treatment
You and your physician should discuss whether treatment is necessary. For minor LLDs in adults 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 one inch. For these small differences, your physician may recommend a shoe lift. A lift fitted to the shoe can often improve your walking and running, as well as relieve back pain caused by LLD. Shoe lifts are inexpensive and can be removed if they are not effective. They do, however, add weight and stiffness to the shoe.
Surgical Treatment
In growing children, legs can be made equal or nearly equal in length with a relatively simple surgical procedure. This procedure slows down the growth of the longer leg at one or two growth sites. Your physician can tell you how much equalization can be gained by this procedure. The procedure is performed under X-ray control through very small incisions in the knee area. This procedure will not cause an immediate correction in length. Instead, the limb length discrepancy will gradually decrease as the opposite extremity continues to grow and "catch up." Timing of the procedure is critical. The goal is to reach equal leg length by the time growth normally ends. This is usually in the mid-to-late teenage years. Disadvantages of this option include the possibility of slight over-correction or under-correction of the limb length discrepancy. In addition, the patient's adult height will be less than if the shorter leg had been lengthened. Correction of significant limb length discrepancy by this method may make a patient's body look slightly disproportionate because of the shorter leg. 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.
The field of leg length inequalities or leg length discrepancy often abbreviated as LLD is well documented and understood. There are two types of short legs; functional (functional LLD) and structural (true LLD). A functional short leg occurs as a result of muscle imbalances, pelvic torsion or other mechanical reasons. The millimeters of ?appearing? short are typically less than 10, and are do not appear on Xray. This article is about structural or anatomical short legs.
Causes
Some children are born with absence or underdeveloped bones in the lower limbs e.g., congenital hemimelia. Others have a condition called hemihypertrophy that causes one side of the body to grow faster than the other. Sometimes, increased blood flow to one limb (as in a hemangioma or blood vessel tumor) stimulates growth to the limb. In other cases, injury or infection involving the epiphyseal plate (growth plate) of the femur or tibia inhibits or stops altogether the growth of the bone. Fractures healing in an overlapped position, even if the epiphyseal plate is not involved, can also cause limb length discrepancy. Neuromuscular problems like polio can also cause profound discrepancies, but thankfully, uncommon. Lastly, Wilms? tumor of the kidney in a child can cause hypertrophy of the lower limb on the same side. It is therefore important in a young child with hemihypertrophy to have an abdominal ultrasound exam done to rule out Wilms? tumor. It is important to distinguish true leg length discrepancy from apparent leg length discrepancy. Apparent discrepancy is due to an instability of the hip, that allows the proximal femur to migrate proximally, or due to an adduction or abduction contracture of the hip that causes pelvic obliquity, so that one hip is higher than the other. When the patient stands, it gives the impression of leg length discrepancy, when the problem is actually in the hip.
Symptoms
Faulty feet and ankle structure profoundly affect leg length and pelvic positioning. The most common asymmetrical foot position is the pronated foot. Sensory receptors embedded on the bottom of the foot alert the brain to the slightest weight shift. Since the brain is always trying to maintain pelvic balance, when presented with a long left leg, it attempts to adapt to the altered weight shift by dropping the left medial arch (shortening the long leg) and supinating the right arch to lengthen the short leg.1 Left unchecked, excessive foot pronation will internally rotate the left lower extremity, causing excessive strain to the lateral meniscus and medial collateral knee ligaments. Conversely, excessive supination tends to externally rotate the leg and thigh, creating opposite knee, hip and pelvic distortions.
Diagnosis
The only way to decipher between anatomical and functional leg length inequalities (you can have both) is by a physical measurement and series of biomechanical tests. It is actually a simple process and gets to the true cause of some runner?s chronic foot, knee, hip and back pain. After the muscles are tested and the legs are measured it may be necessary to get a special X-ray that measures both of your thighs (Femurs) and legs (Tibias). The X-ray is read by a medical radiologist who provides a report of the actual difference down to the micrometer leaving zero room for error. Once the difference in leg length is known, the solution becomes clear.
Non Surgical Treatment
You and your physician should discuss whether treatment is necessary. For minor LLDs in adults 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 one inch. For these small differences, your physician may recommend a shoe lift. A lift fitted to the shoe can often improve your walking and running, as well as relieve back pain caused by LLD. Shoe lifts are inexpensive and can be removed if they are not effective. They do, however, add weight and stiffness to the shoe.
Surgical Treatment
In growing children, legs can be made equal or nearly equal in length with a relatively simple surgical procedure. This procedure slows down the growth of the longer leg at one or two growth sites. Your physician can tell you how much equalization can be gained by this procedure. The procedure is performed under X-ray control through very small incisions in the knee area. This procedure will not cause an immediate correction in length. Instead, the limb length discrepancy will gradually decrease as the opposite extremity continues to grow and "catch up." Timing of the procedure is critical. The goal is to reach equal leg length by the time growth normally ends. This is usually in the mid-to-late teenage years. Disadvantages of this option include the possibility of slight over-correction or under-correction of the limb length discrepancy. In addition, the patient's adult height will be less than if the shorter leg had been lengthened. Correction of significant limb length discrepancy by this method may make a patient's body look slightly disproportionate because of the shorter leg. 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.