leg length discrepancy (LLD)

LEG LENGTH DISCREPANCY (LLD)

Introduction
Cause of leg length Discrepancy
Symptoms of LLD
Effects of LLD
Examination of LLD
Type of LLD
Test of LLD
Management of LLD
Summary

Introduction
Leg length discrepancy (LLD) or Lower limb discrepancy is a condition of unequal lengths of the lower limbs. The discrepancy may be in the femur, or tibia, or both. In some conditions, the whole side is affected, including the upper limbs. However, it is the discrepancy of the lower limbs that causes problems with ambulation, and the focus of this discussion will be about lower limb discrepancy.
When evaluating a child with limb length discrepancy, the cause and changing magnitude during growth must be considered. Asymmetry in limb lengths is not considered pathologic. Discrepancies of 1 cm to 1.5 cm are common, generally do not cause any symptoms, and may not require treatment. The greater the discrepancy, the more a child must compensate his or her normal posture and gait (walking pattern) in day to day life, which can lead to a variety of symptoms, such as functional scoliosis, hip, knee and ankle problems.

Causes of leg length Discrepancy

Structural / anatomical LLD
- Congenital defects
- Trauma (eg: motor vehicle accident)
- Burns
- Infection
- Post-surgical shortening
- Tumor
- Hemi atrophy and hemi hypertrophy

Functional LLD
- Pelvic / lumbar anomaly (e.g.: scoliosis)
- Muscle contracture (e.g.: psoas)
- Asymmetrical rear foot pronation

Symptoms of a leg length discrepancy

The symptoms of a leg length discrepancy vary widely and are often related to the underlying problem causing the discrepancy and the alignment problems that result from it. Every patient experiences symptoms of this condition differently. The following are symptoms of a leg length discrepancy:
1. One leg is obviously shorter than the other (although this is not always obvious) problems with posture (i.e. shoulder may tilt toward shorter side) leading to compensatory or functional scoliosis.

2. Gait problems, such as limping, toe-walking, or rotation of the leg, knee that's chronically hyper extended on the short side and flexed on the long side.

3. Pain in the back, hip, knee, and/or ankle

Effects of Leg length Discrepancy

Problems associated with LLD include
Structural scoliosis, lower back pain, degenerative arthrosis of the lumbar and sacroiliac articulations, long leg degenerative hip and patellofemoral arthrosis, equinus contracture of the ankle, foot callosities, cosmetically unappealing shoe lift or prosthesis, cosmetically unappealing gait disturbance, and increased energy consumption during gait

Examination on leg length Disrepancy

a) Clinical Examination
The initial clinical examination is simple. Examination begins with the patient shoeless and standing with both feet flat on the floor. The patient is viewed from both the front and rear sides. From the rear, relative hip, knee, and foot heights are observed. One-cm blocks are inserted under the shorter limb until the iliac crests are level and the trunk is balanced Leveling the pelvis should eliminate scoliosis if it is a result of LLD.

b) Measuring the Discrepancy
To determine the true discrepancy, the patient is placed in a supine position and then measured (using a tape measure) from the prominence of the anterior iliac crest to the lower prominence of the medial malleous. The relative knee heights are measured with the hips and knees flexed. Foot heights and lengths are obtained by direct observation.

c) Analyzing Gait
Adaptations of walking occur as a means of smoothing gait and minimizing energy expenditure. The patient's gait is evaluated for the compensatory mechanisms (adaptations) of pelvic tilting, long knee flexion, and vaulting on the short side. Another form of compensation, used less frequently, is pelvic internal rotation to lengthen stride. Patients with fixed deformities of the spine, pelvis, hip, knee, or ankle may not be able to use the usual compensation mechanisms. For these patients, walking can be difficult.Analysis of oxygen consumption shows little change in patients with mild LLD; however, easy fatigue is a common complaint of these patients

d) Radiologic Assessment
A history and clinical examination may not always allow for an accurate diagnosis. A screening leg length radiograph, known as a scanogram, aids in making a complete diagnosis.

TYPE
1. True Discrepancy in Length.
2. Apparent Discrepancy in Length

1.True Discrepancy in length
True shortening is the actual shortening or bony shortening.True shortening of one lower limb is present where there is a decrease in the distance between the upper surface of the head of the femur and lower surface of the calcaneus, compared with the other limb. This distance can not be measured accurately by clinical means because of the deeply placed position of the relevant bony points .Accurate measurement is possible only by taking a special radiograph on which both lower limbs from the hips to feet are shown alongside a scale.

For clinical purpose, measurements are taken from anterior superior iliac spine (ASIS) to the tibial platue and tibial platue to tip of the medial malleolus.It is accepted that the ASIS lies at the level of proximal and lateral to the upper surface of the head of the femur, and that part of the talus and calcaneus lies distal to the tip of the medial malleous.

2.Apparent Discrepancy in length
Shortening adopted by the patient or shortening which is visible or shortening which is adopted by patient is known as apparent shortening. Apparent shortening is also due to presence of a fixed adduction or abduction deformity at one hip.

In normal standing, the lower limbs are parallel when seen from in front. To bring the lower limbs into a parallel position when a fixed adduction or abduction deformity is present at one hip, the pelvis is tilted and one knee is flexed. In Presence of fixed adduction deformity, the ASIS on the same side is raised above the horizontal causing apparent shortening of ipsilateral limb. When fixed abduction deformity is present the ASIS is on the opposite side is raised above the horizontal causing apparent shortening of the contra lateral limb (apparent lengthening of the ipsilateral limb)

Test for Leg length Discrepancy

1. True leg length Discrepancy
To determine true leg length discrepancy, place the patient’s legs in precisely comparable position and measure the distance from the ASIS to the medial malleoli of the ankles.ASIS to Tibial platue and Tibial platue to medial malleoli also can measure.

True shortening measure on supine position:
a) Lie down the patient on supine position.
b) Stand on right hand side of the patient.
c) Identify ASIS.
d) Place the measuring tape on ASIS to the medial malleolus and note the total length. Note reading measurement of both lower limbs. (From one fixed bony point to another)
e) Any difference between the two measurements indicates the amount of true shortening present.

True shortening measure on standing position
a) Let stand the patient on erect position with both knees fully extended.
b) Identify both ASIS. ASIS on side of shorter limb will lie at a lower level.
c) Place flat wooden blocks of varying thickness under the foot of shorter limb until the ASIS lie at a horizontal plane.
d) The total height of the wooden blocks used equals the difference in limb length.

To determine in short order where the discrepancy lies (whether in the tibia or in the femur),ask the patient to lie supine , with knees flexed to 90 degree and feet flat on the table .If one knee appears higher than the other , the tibia of the extremity is longer .If one knee projects further anteriorly than other , the femur of the extremity is longer

2. Apparent leg length Discrepancy
Established that there is no true leg length discrepancy before testing for an apparent discrepancy in which there is no true bony inequality. Apparent shortening may stem from pelvic obliquity or from adduction or flexion deformity in the hip joint. During inspection pelvic obliquity manifest itself as uneven anterior or posterior superior iliac spines while the patient is standing.

The apparent lengths of the lower limbs are measured from a fixed point such as xiphisternum or umbilicus to the tip of the malleolus of both legs respectively.
a) Lie the patient on supine position with legs in neutral position as possible.
b) Measure the distance from xiphisternum or umbilicus to medial malleoli of the ankle respectively.
c) Difference between the measurements for each lower limb indicates the presence of a fixed adduction or abduction deformity at one hip, but only if true shortening or lengthening is absent.

Management of LLD

1. Non-surgical management
a) Compensation

2. Surgical management
a) Epiphysiodesis
b) Shortening
c) Lengthening

1. Non-surgical management
A lift is indicated when the inequality affects the gait pattern, shoe wear, function, or causes pain. A 1-cm lift can fit comfortably inside of the shoe; however, larger inserts can render the foot unstable in the shoe. Lifts placed on the sole of the shoe function well up to approximately 3 cm.Beyond this, the shoe becomes heavy and awkward. Compliance depends on the patient and family.

a) Compensation
Leg length inequality of 2 cm or less is usually not a functional problem. Often, leg length can be equalized with a shoe lift, which usually corrects about two thirds of the leg length inequality. Up to 1 cm can be inserted in the shoe. For larger leg length inequalities, the shoe must be built up. This need to be done for every shoe worn, thus limiting the type of shoe that the patient can wear. Leg length inequalities beyond 5 cm are difficult to treat with a shoe lift. The shoe looks unsightly, and often the patient complains of instability with such a large lift. A foot-in-foot prosthesis can be used for larger leg length inequalities. This is often done as a temporizing measure for young children with significant leg length inequalities. The prosthesis is bulky, and a fixed equinus contracture may result.


2. Surgical management
a) Epiphysiodesis
b) Shortening
c) Lengthening

a) Epiphysiodesis

Epiphysiodesis is a reliable procedure that inhibits growth with few complications. This obviously cannot be done on skeletally mature patients, and the final leg length inequality and the degree of growth inhibition need to be predicted and are subject to errors.Because the procedure effectively shortens the longer leg and is usually done on the uninvolved side. It may be unappealing to the patient and family.

b) Shortening

Shortening techniques can be used after skeletal maturity to achieve leg length equality. Shortening can be done in the proximal femur using a blade plate or hip screw, in the mid-diaphysis of the femur using a closed intramedullary (IM) technique or in the tibia. Shortening is an accurate technique and involves a much shorter convalescence than lengthening techniques.


c) Lengthening
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

Summary
Leg length discrepancy is a condition of unequal lengths of the lower limbs. The discrepancy may be in the femur, or tibia, or both. When evaluating a child with limb length discrepancy, the cause and changing magnitude during growth must be considered. LLD is associated with burn, infection, trauma, muscle contracture, congenital defect etc. LLD results lower back pain, scoliosis, ugly gait, more energy consumption etc. Discrepancies of 1 cm to 1.5 cm are common, generally do not cause any symptoms, and may not require treatment. LLD are categories on true discrepancy and apparent discrepancy. True discrepancy is bony or structure discrepancy, apparent discrepancy is adopted or functional discrepancy.Multi-disciplinary approach is necessary for effective management of LLD.Which include orthopedic doctor, orthotist & prosthetist, physiotherapist etc.