Differences between lengths of the two upper extremities (upper and/or lower arms) or between the lengths of the two lower extremities (upper and/or lower legs) are called limb length discrepancy (LLD). A limb length discrepancy may be due to a normal variation that we all have between the two sides of our bodies, or it may be due to other causes. Some differences are so common that they are normal and need no treatment. For example, one study reported that 32 percent of 600 military recruits had a 5mm to 15mm (approximately 1/5 to 3/5 inch) difference between the lengths of their two lower extremities; this is a normal variation. Greater differences may need treatment because a discrepancy can affect a patient?s well being and quality of life.
Limb-length conditions can result from congenital disorders of the bones, muscles or joints, disuse or overuse of the bones, muscles or joints caused by illness or disease, diseases, such as bone cancer, Issues of the spine, shoulder or hip, traumatic injuries, such as severe fractures that damage growth plates.
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.
Leg length discrepancy may be diagnosed during infancy or later in childhood, depending on the cause. Conditions such as hemihypertrophy or hemiatrophy are often diagnosed following standard newborn or infant examinations by a pediatrician, or anatomical asymmetries may be noticed by a child's parents. For young children with hemihypertophy as the cause of their LLD, it is important that they receive an abdominal ultrasound of the kidneys to insure that Wilm's tumor, which can lead to hypertrophy in the leg on the same side, is not present. In older children, LLD is frequently first suspected due to the emergence of a progressive limp, warranting a referral to a pediatric orthopaedic surgeon. The standard workup for LLD is a thorough physical examination, including a series of measurements of the different portions of the lower extremities with the child in various positions, such as sitting and standing. The orthopaedic surgeon will observe the child while walking and performing other simple movements or tasks, such as stepping onto a block. In addition, a number of x-rays of the legs will be taken, so as to make a definitive diagnosis and to assist with identification of the possible etiology (cause) of LLD. Orthopaedic surgeons will compare x-rays of the two legs to the child's age, so as to assess his/her skeletal age and to obtain a baseline for the possibility of excessive growth rate as a cause. A growth chart, which compares leg length to skeletal age, is a simple but essential tool used over time to track the progress of the condition, both before and after treatment. Occasionally, a CT scan or MRI is required to further investigate suspected causes or to get more sophisticated radiological pictures of bone or soft tissue.
Non Surgical Treatment
Treatment depends on what limb has the deformity and the amount of deformity present. For example, there may be loss of function of the leg or arm. Cosmetic issues may also be a concern for the patient and their family. If there are problems with the arms, the goal is to improve the appearance and function of the arm. Treatment of leg problems try to correct the deformity that may cause arthritis as the child gets older. If the problem is leg length, where the legs are not "equal," the goal is equalization (making the legs the same length). Treatment may include the use of adaptive devices, prosthesis, orthotics or shoe lifts. If the problem is more severe and not treatable with these methods, then surgery may be necessary.
The bone is lengthened by surgically applying an external fixation device to the leg. The external fixator, a scaffold-like frame, is connected to the bone with wires, pins, or both. A small crack is made in the bone and the frame creates tension when the patient or family member turns its dial. This is done several times each day. The lengthening process begins approximately five to 10 days after surgery. The bone may lengthen 1 millimeter per day, or approximately 1 inch per month. Lengthening may be slower in a bone that was previously injured. It may also be slower if the leg was operated on before. Bones in patients with potential blood vessel abnormalities, such as cigarette smokers, may also need to be lengthened more slowly. The external fixator is worn until the bone is strong enough to support the patient safely. This usually takes about three months for each inch. Factors such as age, health, smoking and participation in rehabilitation can affect the amount of time needed.