By: esiwcala eratbuso
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|Thursday, 4-Jul-2013 04:55
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What is leg-length discrepancy?
Many people will have one leg longer than the other, and often this is why we have one foot larger than the other. Usually the larger foot corresponds to the longer leg, as it has to push down more on the foot, causing the arch to lower (pronate), and the foot to elongate.
Leg-length discrepancies are not uncommon. But most of the time the difference is small, and has no noticeable effect on appearance and function. The problem arises when the difference is too obvious, especially in the case of the lower limb.
Length of limbs
Anatomical/structural - meaning one limb is actually shorter than the other due to a smaller femur (thighbone) or tibia (lower leg bone); also called true limb length discrepancy.
Functional - in that both limbs are equal in length, but the hips are either dislocated or unstable, making one hip higher than the other one. As a result, one limb appears shorter than the other limb, without an actual difference in the length of two. This type of length discrepancy is also called apparent limb length discrepancy.
The difference in the length may range from less than one centimetre to six centimetres, or more. The greater the difference, the greater is the disturbance in the normal biomechanics of the lower limbs, as the body has to alter its posture and functioning to compensate for the difference in leg length. A difference of one cm is mild and does not cause much problem. However, above three-four cm the discrepancy becomes more obvious and has profound effects on posture and function. The extent of the problem will also be determined by the person’s activity level.
Trauma (bone fracture)
A fractured bone may heal with a shortened length, especially when the bone has sustained multiple fractures (i.e., it is broken in many pieces), or heals in an overlapped position.
In children, a broken bone may become shorter if the fracture has occurred near the end of the bone. As the growth of the bone occurs near its ends, a fractured end damages the growing cells of the bone, leading to slower growth and therefore, a shorter bone/limb length.
However, in children, a fractured bone may sometimes show a faster growth rate than the other bone, also leading to a discrepancy.
A bone disease, occurring during infancy or early childhood can lead to significant discrepancy. An infection affecting the growth area of the bone (near bone ends) destroys the growing cell leading to retarded growth and a shorter limb. Examples include:
• osteomyelitis (infection of the bone or bone marrow)
• septic arthritis (infection of the joints)
• tuberculosis of bones and joints
• juvenile arthritis: an autoimmune disease in children, causing inflammation of the joints.
Functional or Apparent LLD can occur due to:
• developmental dislocation of the hip
• neuromuscular problems such as polio, cerebral palsy, etc.
• spinal scoliosis: a sideways-curved spine that results in uneven hips and limb lengths
• coxa vara: a congenital or development deformity of the hip that leads to a shorter leg.
Moreover, a previous surgical procedure involving hip or knee joint replacement or a prolonged immobilisation (such as wearing a leg brace for long), or accidents, may also lead to a shorter length of the given limb.
The difference in length not only affects the gait of the person, but also disturbs the whole lower limb biomechanics, as the body tries to adapt to, or compensate for, the difference. Moreover, the symptoms not only depend upon the difference in leg length but also on the underlying cause.
• There could be limping or toe walking; a difference of about three-four cm is enough to cause an alteration in normal walking patterns. Moreover, the knee on the longer side becomes flexed.
• A person has to exert more effort as they walk and the longer limb takes more of the pressure. There is the risk of development of degenerative arthritis in the hip of the longer limb.
• Postural changes - the shoulders lean towards the shorter side, the spine also becomes curved sideways (functional scoliosis).
• It may also cause lower back, hip, and knee pains.
Additionally, symptoms could include any problem that is present on one foot and not the other. They can be as diverse as corns and callouses, plantar fasciitis, knee problems, bunions, capsulitus, heel pain, metatarsalgia, and even tendonitis.
A detailed history, as well as a careful examination, is essential to discover the underlying cause of the problem and to rule out any factors that cause an apparent length discrepancy such as hip displacement, joint contractures or sideways spinal deviation (scoliosis).
The length of the limbs is measured in two ways:
• the actual length of the limb - from hip to ankle.
• the apparent length - from navel to ankle.
The difference in length is further assessed by placing wooden blocks of different sizes under the shorter limb.
X-rays and CT scans assist in accurate measurement of the discrepancy and in diagnosing the underlying condition.
When dealing with discrepancies, the activity level of the patient, as well as the amount of limb length difference has to be considered. Treatment is generally aimed at reducing the difference to less than one cm at completion of growth. A discrepancy less than two cm is often asymptomatic and does not require any treatment. In a few cases, a heel lift is all that is required. A discrepancy greater than three cm usually requires treatment.
Non-surgical options include adding a heel lift or a shoe lift to compensate for the deficiency. Surgical options include shortening the longer limb or lengthening the shorter limb. The treatment of leg-length discrepancy requires months, even years, for completion and requires patience and full cooperation of the patient as well as the family.
Diagnosis is critical here, and appropriate treatment may also include strapping, orthotics and even referral for physiotherapy or to an orthopaedic specialist. Often, people will go through life with one leg longer than the other and have no problems at all.
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