How Might Leg Length Discrepancy Have An Impact On Gait

Overview

The majority of people in the world actually have some degree of leg length discrepancy, up to 2cm. One study found that only around 1/4 of people have legs of equal lengths. LLD of greater than 2cm is relatively rare, however, and the greater the discrepancy, the greater the chances of having a clinical problem down the road. A limp generally begins when LLD exceeds 2cm and becomes extremely noticeable above 3cm. When patients with LLD develop an abnormal gait, one of the debilitating clinical features can be fatigue because of the relatively high amount of energy needed to walk in the new, inefficient way. Poliomyelitis, or polio, as it is more commonly known, used to account for around 1/3 of all cases of LLD, but due to the effectiveness of polio vaccines, it now represents a negligible cause of the condition. Functional LLD, described above, usually involves treatment focused on the hip, pelvis, and/or lower back, rather than the leg. If you have been diagnosed with functional LLD or pelvic obliquity, please ask your orthopaedic surgeon for more information about treatment of these conditions.Leg Length Discrepancy

Causes

Some causes of leg length discrepancy (other than anatomical). Dysfunction of the hip joint itself leading to compensatory alterations by the joint and muscles that impact on the joint. Muscle mass itself, i.e., the vastus lateralis muscle, pushes the iliotibial band laterally, causing femoral compensations to maintain a line of progression during the gait cycle. This is often misdiagnosed as I-T band syndrome and subsequently treated incorrectly. The internal rotators of the lower limb are being chronically short or in a state of contracture. According to Cunningham's Manual of Practical Anatomy these are muscles whose insertion is lateral to the long axis of the femur. The external rotators of the hip joint are evidenced in the hip rotation test. The iliosacral joint displays joint fixations on the superior or inferior transverse, or the sagittal axes. This may result from many causes including joint, muscle, osseous or compensatory considerations. Short hamstring muscles, i.e., the long head of the biceps femoris muscle. In the closed kinetic chain an inability of the fibula to drop inferior will result in sacrotuberous ligament loading failure. The sacroiliac joint dysfunctions along its right or left oblique axis. Failure or incorrect loading of the Back Force Transmission System (the longitudinal-muscle-tendon-fascia sling and the oblique dorsal muscle-fascia-tendon sling). See the proceedings of the first and second Interdisciplinary World Congress on Low Back Pain. Sacral dysfunction (nutation or counternutation) on the respiratory axis. When we consider the above mentioned, and other causes, it should be obvious that unless we look at all of the causes of leg length discrepancy/asymmetry then we will most assuredly reach a diagnosis based on historical dogma or ritual rather than applying the rules of current differential diagnosis.

Symptoms

Many people walk around with LLD?s of up to 2 cm. and not even know it. However, discrepancies above 2 cm. becomes more noticeable, and a slight limp is present. But even up to 3 cm. a small lift compensates very well, and many patients are quite happy with this arrangement. Beyond 3 cm. however, the limp is quite pronounced, and medical care is often sought at that point. Walking with a short leg gait is not only unsightly, but increases energy expenditure during ambulation. It could also put more stress on the long leg, and causes functional scoliosis. Where the discrepancy is more severe, walking becomes grotesque or virtually impossible.

Diagnosis

A qualified musculoskeletal expert will first take a medical history and conduct a physical exam. Other tests may include X-rays, MRI, or CT scan to diagnose the root cause.

Non Surgical Treatment

After the leg length discrepancy has been identified it can be categorized in as structural or functional and appropriate remedial action can be instigated. This may involve heel lifters or orthotics being used to level up the difference. The treatment of LLD depends on the symptoms being experienced. Where the body is naturally compensating for the LLD (and the patient is in no discomfort), further rectifying action may cause adverse effects to the biomechanical mechanism of the body causing further injury. In cases of functional asymmetry regular orthotics can be used to correct the geometry of the foot and ground contact. In structural asymmetry cases heel lifts may be used to compensate for the anatomic discrepancy.

Leg Length Discrepancy

Surgical Treatment

Lengthening is usually done by corticotomy and gradual distraction. This technique can result in lengthenings of 25% or more, but typically lengthening of 15%, or about 6 cm, is recommended. The limits of lengthening depend on patient tolerance, bony consolidation, maintenance of range of motion, and stability of the joints above and below the lengthened limb. Numerous fixation devices are available, such as the ring fixator with fine wires, monolateral fixator with half pins, or a hybrid frame. The choice of fixation device depends on the desired goal. A monolateral device is easier to apply and better tolerated by the patient. The disadvantages of monolateral fixation devices include the limitation of the degree of angular correction that can concurrently be obtained; the cantilever effect on the pins, which may result in angular deformity, especially when lengthening the femur in large patients; and the difficulty in making adjustments without placing new pins. Monolateral fixators appear to have a similar success rate as circular fixators, especially with more modest lengthenings (20%).

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