Small or mild length leg discrepancies (LLD), i.e., below 3.0 cm, have been considered as enough to cause orthopaedic changes such as lumbar pain, stress fractures and osteoarthritis on lower limbs (LLLL) joints. In addition to the classification by its magnitude, discrepancies can also be categorized according to etiology, being structural when a difference is noted between bone structures' length or functional as a result of mechanical changes on the lower limb, and are found in 65% - 70% of the healthy population.
Sometimes the cause of LLD is unknown, yet the pattern or combination of conditions is consistent with a certain abnormality. Examples include underdevelopment of the inner or outer side of the leg (hemimelias) or (partial) inhibition of growth of one side of the body of unknown cause (hemihypertrophy). These conditions are present at birth, but the limb length difference may be too small to be detected. As the child grows, the LLD increases and becomes more noticeable. In hemimelia, one of the two bones between the knee and the ankle (tibia or fibula) is abnormally short. There also may be associated foot or knee abnormalities. Hemihypertrophy or hemiatrophy are rare conditions in which there is a difference in length of both the arm and leg on only one side of the body. There may also be a difference between the two sides of the face. Sometimes no cause can be found. This type of limb length is called idiopathic. While there is a cause, it cannot be determined using currect diagnostic methods.
The effects of a short leg depend upon the individual and the extent of discrepancy. The most common manifestation if a lateral deviation of the lumbar spine toward the short side with compensatory curves up the spine that can extend into the neck and even impacts the TMJ. Studies have shown that anterior and posterior curve abnormalities also can result.
Asymmetry is a clue that a LLD is present. The center of gravity will shift to the short limb side and patients will try to compensate, displaying indications such as pelvic tilt, lumbar scoliosis, knee flexion, or unilateral foot pronation. Asking simple questions such as, "Do you favor one leg over the other?" or, "Do you find it uncomfortable to stand?" may also provide some valuable information. Performing a gait analysis will yield some clues as to how the patient compensates during ambulation. Using plantar pressure plates can indicate load pressure differences between the feet. It is helpful if the gait analysis can be video-recorded and played back in slow motion to catch the subtle aspects of movement.
Non Surgical Treatment
Non-surgical treatment can be effective. A shoe lift may be recommended if the leg length difference is less than 1 inch. More significant leg length discrepancies may require a surgical procedure. In children, surgical procedures are available to help make leg lengths more equal.
Surgeries for LLD are designed to do one of three general things ? shorten the long leg, stop or slow the growth of the longer or more rapidly growing leg, or lengthen the short leg. Stopping the growth of the longer leg is the most commonly utilized of the three approaches and involves an operation known as an epiphysiodesis , in which the growth plate of either the lower femur or upper tibia is visualized in the operating room using fluoroscopy (a type of real-time radiographic imaging) and ablated , which involves drilling into the region several times, such that the tissue is no longer capable of bone growth. Because the epiphyseal growth capabilities cannot be restored following the surgery, proper timing is crucial. Usually the operation is planned for the last 2 to 3 years of growth and has excellent results, with children leaving the hospital within a few days with good mobility. However, it is only appropriate for LLD of under 5cm.