Leg Length Discrepancy

What Is Leg Length Discrepancy?

Leg length discrepancy (LLD) is a condition involving prominent unevenness among both limbs, with a widespread situation in almost 70 percent of the population. The average value of the difference in lengths between both legs is 0.5 cm (centimeter) to 2 (centimeter), and it can range from minor to significant shortening. The leg length discrepancy is also called leg length insufficiency or anisomelia. LLD can be mentally tiring as it limits people's normal functions like walking, running, posture, and balance. The LLD is considered significant if the amount of differentiation is more than 20 mm (millimeter).

What Are the Types of Leg Length Discrepancies?

Leg length discrepancy can be classified into three types.

• Anatomical LLD: As the name suggests, it occurs as a structural deformity due to bony discrepancies. These bony discrepancies can occur due to multiple reasons, mainly developmental disturbances during the intrauterine life or period of maturation of the bones, like adolescence.

• Functional LLD: It occurs due to recurrent or improper usage of the bony tissue and adjoining muscle fibers. Increased load and strain on specific areas lead to distortion of the surrounding soft tissue resulting in deformity. It is commonly seen in muscle weakening or inflexibility of the pelvis, foot, or ankle.

• Environmental LLD: It is a combination of structural and functional disturbances where the functional degradation occurs due to bony anatomical discrepancies like in the ankle with bony prominence; the pressure exhibited on that area causes the muscle to weaken.

What Are the Factors Which Cause Leg Length Discrepancy?

The causative factors for the type of LLD depend on the category it falls under. The leg length discrepancy can be divided into true and functional LLD. A true LLD is anatomical, and the functional LLD occurs due to the associated activities or adjoining soft tissues. The factors causing Leg length discrepancy are:

True LLD:

• Idiopathic congenital developmental abnormalities.

• Trauma during skeletal maturity.

• Fracture.

• Osteonecrosis conditions like Legg-Calve-Perthes disease.

• Infections.

• Malignancies.

Functional LLD:

• Degeneration of soft tissues.

• Joint stiffness.

• Mobility of the ligament.

• Malalignment of the axial bone.

• Increased flexion of the ankle.

What Are the Clinical Features of Leg Length Deformity?

Leg length discrepancies show an incidence of almost 70 percent globally, and the height difference is around two to five cm (centimeters), with only 20 percent of cases visibly more than five centimeters in incidence. Patients with leg length deformity have an uneven distribution of body mass, also known as center of mass (CoM) displacement leading to uneven workload resulting in muscle weakness. The clinical symptoms are:

• Clinically visible deformity in height.

• Pain due to uneven stretching of the limbs.

• Reduced surface joint loading.

• Increased strain on joint and bony structures.

• Bent knee.

• Lower back pain.

The actions altered by LLD during walking, standing, and running are associated with deformities of bone and soft tissue as follows:

LLD While Standing:

• Scoliosis.

• Increased muscle activity.

LLD While Walking:

• Abnormal gait posture.

• Increased vertical displacement (VD) of CoM leads to more energy expenditure.

• Decreased standing time.

• Shorter walking strides.

• Decreased walking pace.

• Increased walking sounds.

LLD While Running:

There is a more significant impact of LLD in running than in walking because of the increased velocity of force exerted during running, which shows the following symptoms.

• Increased vertical oscillation due to uneven distribution of weight or weight imbalances.

• Half the standing time compared to walking.

• Increased strain in lower limbs.

LLD in Adjoining Structures Include:

• Hip pain.

• Fractures of the bone due to stress and strain involving the tibia, femur, and metatarsals.

• Pain in the associated functional muscles.

How Is Leg Length Discrepancy Evaluated?

Imaging methods and clinical methods can evaluate LLD.

Clinical Methods: The clinical techniques are easier to use, more patient-friendly, and cost-effective. It uses measuring tapes and sanding blocks, and the distance of difference calculated is :

• From the most prominent part of the hip to the ankle.

• From the belly button to the ankle joint.

Imaging Methods: The imaging techniques of choice for LLD are:

• Computed Tomography (CT) - Computed tomography is a three-dimensional imaging technique used to examine the bone along with its orientation to cartilage and tissues.

• Radiographs (X-ray) - X-rays are two-dimensional imaging methods used to examine the condition and structure of the bone.

• Ultrasonography - These are scanning techniques used to examine the organs using sound waves.

• Magnetic Resonance Imaging (MRI) - This imaging technique is mainly used to examine soft tissue elements like organs, tissues, glands, and cartilage.

These methods study the structure of the hip and the legs. The computerized images help measure the length between the hip and the ankle. Also, the imaging methods are more precise than the clinical methods.

How Is Leg Length Discrepancy Treated?

The above-mentioned clinical features can be present over time before becoming prominently visible; hence, taking primary care improves the quality of life. The clinical modalities of LLD can be either clinical or non-clinical management, where clinical management includes surgical procedures, and non-clinical management enhances the patient's lifestyle.

The non-surgical treatment options are:

• Insole inserts in shoes.

• High sole shoes.

• Using a splint or braces is called an orthosis.

The surgical management methods are:

• Retarding or stopping the growth of the longer leg.

• Shortening the longer limb or lengthening the shorter limb through osteotomy procedures.

• Using implants for leg lengthening.

Differential Diagnosis:

The clinical conditions which occur similar to LLD and to be ruled out before diagnosis are:

• Juvenile rheumatoid arthritis.

• Ollier's disease.

• Polymylites.

• Avascular necrosis.

• Neurofibromatosis.

Conclusion

Leg length discrepancy or anisomelia, as discussed above, prevails very commonly. Though the cause can be idiopathic or a developmental deformity, it is a condition that can be both mentally and physically tiring for the patient. But with an early diagnosis which prevents or restricts pain and muscle wasting from the beginning, with the right treatment plan and with the help of non-surgical aids like shoe sole inserts or braces and physiotherapy for core strengthening, which helps in correcting the gait and posture, the quality of life and lifestyle of the patient can be drastically improved.