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Limb Length Discrepancy (LLD)

    • What is limb length discrepancy?

      Limb length discrepancy

      Limb length discrepancy (LLD) or limb length inequality refers to a condition where one arm or one leg is shorter than the other. Differences in arm length are less likely to affect normal function compared to differences in leg length, which impacts day-to-day activities such as walking and playing sports.

      The difference in leg length can vary widely, from less than an inch to several inches. Significant differences are more likely to affect a person’s posture while standing or walking. This can lead to problems in the hip, knee and ankle and cause an apparent scoliosis (abnormal curvature of the spine).

      LLD can be categorized as a static or progressive deformity:

      • Static - meaning the discrepancy stays the same, could be due to a malunion of a fracture of the lower limb bones.

      • Progressive - meaning the discrepancy can worsen with further growth, can be due to an injury to the growth plate; or a condition present from birth (congenital).

    • What are the causes of limb length discrepancy?

      Discrepancies in leg length can exist from birth. These may be due to conditions that interfere with the alignment of the hip, such as developmental dysplasia of the hip (DDH), or there may be no known cause.

      Other causes of leg length discrepancy include:

      • Bone injuries

        Fractures or trauma to the bone can affect its growth. For example, bone that has been broken in multiple places, with severe damage to the skin and muscle, can heal shorter than it was before. However, a child with a broken leg bone can sometimes go through accelerated growth that causes it to become longer than the bone in the other leg. This is more common in young children who experience fractures of the thigh bone.

      • Bone infection

        Bone infection (osteomyelitis) can damage the growth plate and lead to limb length discrepancies.

      • Bone tumours

        Bone tumours and its treatment can affect the rate of bone growth, leading to discrepancies in length.

      • Neuromuscular conditions

        Paralytic disorders like cerebral palsy can affect alignment and posture, and cause discrepancy.

    • What are the symptoms of limb length discrepancy?

      Symptoms of leg length discrepancy varies based on the difference in leg length, its cause and the presence of other health conditions. These include:

      • Problems with gait (pattern of walking), such as a limp, walking on toes or leaning to one side
      • Abnormal posture such as a tilting shoulder or having the ankle on the shorter leg chronically hyperextended
      • Pain in the ankles, knees, hip, or back as a result of compensating for the difference in leg length
      • Functional scoliosis (abnormal curvature of the spine)
      • Back pain
      • Osteoarthritis
    • How is limb length discrepancy diagnosed?

      In children, leg length discrepancy is often first noticed by parents. To properly diagnose this condition in children, a paediatric orthopaedist will examine the child’s medical history and perform a physical examination. This would include observing how the child sits, stands and moves around. If the child is old enough to walk, a gait analysis will be performed to see the way he or she walks and whether the child compensates for leg length discrepancy by walking differently.

      The difference in limb length can be measured in different ways. A measurement may be obtained of the limbs while the child is lying at rest. Alternatively, a series of blocks will be placed under the shorter leg until the hips are level, and the blocks measured for height.

      To get a more precise measurement of the difference in limb length, imaging tests may be recommended. This helps the doctor to identify the cause or origin of the problem so that the appropriate treatment can be determined. They may include one or more of the following:

    • How is limb length discrepancy treated?

      Treatment for leg length discrepancy will depend on its cause, severity and the child’s age. In many cases, minor differences in leg length can be corrected by wearing a lift or insert in one shoe.

      For more significant discrepancies, surgery may be recommended in order to obviate the complications highlighted above. Surgery procedures such as:

      Epiphysiodesis

      This procedure may be recommended for children who are still growing, to slow or stop the rate of growth in the longer leg, allowing the shorter limb to catch up in length. It is performed through small incisions around the knee and timed so that the leg lengths are equal by the time the child’s growth ends in their mid-to-late teens.

      Limb Shortening

      This is an option in cases with smaller discrepancies. This is done by removing a segment of bone from the middle of the longer limb. A metal plate or rod is inserted to hold the bones in place while it heals.

      Limb Lengthening

      This procedure is usually reserved for patients with significant discrepancies and may be performed externally or internally. Both types require regular follow-up visits to the doctor to monitor treatment progress, followed by extensive rehabilitation that includes physiotherapy.

      • External lengthening

        External lengthening involves cutting the bone in the shorter leg and inserting a frame, also known as an external circular-ring fixator, that is connected to the bone with pins or wires. The frame is manually turned to gradually pull the bones apart, allowing new bone to grow.

        The frame is worn until the newly-grown bone is strong enough to support the patient. During this time, careful maintenance and cleaning of the pins are important to prevent infection.

      • Internal lengthening

        Internal lengthening similarly involves cutting the bone in the shorter leg. An expandable metal rod is surgically implanted and gradually lengthened, pulling the bones apart and allowing new bone to grow in its place. The process may take months, but the advantage is that it has less potential for wound complications.

    • What are the complications and related diseases of limb length discrepancy?

      Leg length discrepancies, if significant, can lead to several complications. Left untreated, the patient may experience back pain, pain from osteoarthritis, functional scoliosis, problems with gait and joint problems.

      However, treatment must be titrated to each individual. Some may do well with a simple insert into the shoe, while others may require surgery. Surgery in itself should not be taken lightly as there are potential pitfalls and complications that may occur.

      If in doubt, it is best to consult with a paediatric orthopaedic surgeon.

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