Leg length discrepancy (LLD) refers to a condition where one leg is shorter than the other. The difference can range from subtle to significant. While many individuals have a minor difference that causes no issues, a more substantial discrepancy can affect movement and lead to physical symptoms.
Understanding Leg Length Discrepancy
Leg length discrepancies are categorized into two types: structural and functional. Structural LLD involves an actual difference in the bone lengths of the leg, typically affecting the femur (thighbone) or tibia (shinbone). This type arises from an anatomical shortening or lengthening of the leg bones.
Functional LLD occurs when the leg bones are of equal length, but other factors create an apparent difference. This can stem from issues like pelvic tilt, scoliosis (a sideways curvature of the spine), muscle imbalances, or joint contractures. These conditions can cause one hip to be positioned higher, making one leg appear shorter.
Causes of structural LLD can be congenital or develop over time. Developmental issues, such as growth plate injuries in children, certain bone diseases, or infections, may lead to uneven growth. Acquired factors like poorly healed bone fractures, previous surgeries (such as hip or knee replacements), or even radiation therapy can result in a structural discrepancy.
Common symptoms include a visible limp or an altered walking pattern, sometimes with toe-walking on the shorter leg. Individuals may also experience pain in the back, hip, or knee due to the uneven stress placed on these joints. Postural problems, such as one shoulder sitting higher than the other, can indicate leg length discrepancy.
Identifying Leg Length Discrepancy
Diagnosing a leg length discrepancy begins with a clinical examination. During the examination, the doctor may visually observe the patient’s posture and gait, looking for signs like an uneven pelvis or a noticeable limp. Physical measurements are also taken, often using measuring tapes or by placing blocks of varying heights under the shorter leg until the pelvis appears level.
Imaging techniques are employed for precise measurement of bone lengths. Standing X-rays, often referred to as scanograms or orthoroentgenograms, are commonly used. These specialized X-rays involve taking images of the hips, knees, and ankles with a ruler in the frame to accurately measure the length of the leg bones.
Computed tomography (CT) scanograms provide detailed images for precise measurement, particularly when a more in-depth view of bone and soft tissue structures is needed. Accurate measurement is important for determining the exact nature of the discrepancy, whether structural or functional, and for guiding the appropriate course of treatment. This process helps tailor interventions to individual needs.
Non-Surgical Approaches to Correction
For leg length discrepancies that are mild or functional, non-surgical approaches are often the first approach. One common method involves the use of shoe lifts or orthotics (insoles) to compensate for the length difference. These devices are placed inside or attached to the sole of the shoe to elevate the shorter leg, effectively equalizing leg lengths and improving balance.
Shoe lifts are recommended for discrepancies less than 2 to 2.5 centimeters. They can help alleviate symptoms such as back, hip, or knee pain by promoting more even weight distribution and reducing compensatory postures. For functional LLD, physical therapy plays a role in addressing underlying causes.
Physical therapy programs include exercises to improve posture, strengthen weakened muscles, and stretch tight soft tissues. This can help correct imbalances in the pelvis and spine that contribute to an apparent leg length difference. By improving muscle balance and flexibility, physical therapy can enhance gait mechanics and reduce discomfort, particularly in cases where the discrepancy is not due to bone length.
Surgical Options for Correction
When leg length discrepancies are significant or structural and not adequately managed non-surgically, surgical interventions may be considered. One surgical option, typically for growing children, is epiphysiodesis. This procedure involves slowing or stopping the growth of the longer leg’s growth plate, allowing the shorter leg to naturally catch up in length over time.
Epiphysiodesis is used for discrepancies between 2 and 6 centimeters. The surgeon can perform this by drilling the growth plate, placing screws across it, or tethering it with plates to inhibit further growth. The timing of this procedure is important, as it relies on the child’s remaining growth to achieve leg length equality.
For more substantial discrepancies or in individuals who have completed their growth, limb lengthening procedures are an option. These surgeries involve actively lengthening the shorter bone. One method utilizes external fixators, metal frames attached to the bone with pins or wires outside the body. After the bone is surgically cut (osteotomy), the external fixator is gradually adjusted to pull the bone segments apart, stimulating new bone growth in the gap.
Internal lengthening nails are another advancement. These implants are placed inside the bone, eliminating the need for external hardware. After an osteotomy, a magnetic or motorized mechanism within the nail is activated externally, slowly extending the bone. This gradual distraction process encourages the body to form new bone, ultimately increasing the limb’s length. Both external fixators and internal nails require a commitment to a lengthy process of bone regeneration and rehabilitation.