Blounts Disease

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Blounts Disease (Bowlegs) is common in toddlers and young children. The condition is called physiologic tibia varum when it's a normal variation and the child will grow out of it. Most toddlers have bowlegs from positioning in the uterus. This curvature remains until the muscles of the lower back and legs are strong enough to support them in the upright position.

In some cases abnormal growth of the bone causes the bowing to get worse instead of better over time. This condition is called Blounts disease or pathologic tibia varum.

Blounts disease becomes obvious between the ages of two and four as the bowing gets worse. Overweight adolescents or teenagers can also develop Blounts disease.

Bowing of one or both legs that may:

  • Be rapidly progressive
  • Appear asymmetric
  • Primarily occur just below the knee

  • Causes:
    There are three types of tibia varum based on the age it begins:
    1) infantile (less than three years old),
    2) juvenile (occurs between four and 10 years), and
    3) adolescent (11 years of age and older).

    Physiologic tibia varum occurs between the ages of 15 months to three years. There's no need for treatment for this normal stage of development. But it's not always clear at this age if the tibia varum is a normal variation or Blount's disease.

    Blount's disease is caused by a growth disorder of the upper part of the tibial bone. Toddlers or children who are large or overweight for their age and who walk early are most often affected. As the child walks, the repeated stress and compression of extra weight slows or stops growth of the developing bone. When only one side of the tibia stops growing, there are abnormal changes in bone alignment resulting in this curvature or bowing of the bone.

    There can be other causes of bowed legs in toddlers or young children. Metabolic disorders such as a deficiency of vitamin D causing rickets is more common in other countries. In the United States many of our foods are fortified with vitamin D to prevent this problem. In a small number of children, vitamin D deficiency occurs as a result of a genetic abnormality. The child cannot absorb or metabolize vitamin D.

    Juvenile or adolescent Blounts disease is usually caused by obesity but can be the result of infection or trauma that disrupted the medial growth plate.

    Treatment depends on the age of the child and the stage of the disease. Between ages birth and two, careful observation or a trial of bracing (also called orthotics may be done. If the child doesn't receive treatment, Blount's disease will gradually get worse with more and more bowlegged deformity. Surgery may be needed to correct the problem. For the obese child, weight loss is helpful but often difficult.

    Nonsurgical Treatment
  • Most of the time bowlegs or genu varum resolves on its own with time and growth. No specific treatment is needed unless the problem persists after age two.
  • In the case of Blount's disease aggressive treatment is needed. Severe bowing before the age of three is braced with a hip-knee-ankle-foot orthosis or knee-ankle-foot orthosis. Bracing is used 23 hours a day. As the bone straightens out with bracing, the orthotic is changed every two months or so to correct the bowlegged position.

  • Surgery:
  • Surgical correction may be needed especially for the younger child with advanced stages of tibia varum or the older child who has not improved with orthotics. Surgery isn't usually done on children under the age of two because at this young age, it's still difficult to tell if the child has Blount's or just excessive tibial bowing. A tibial osteotomy is done before permanent damage occurs. Brace treatment for adolescent Blount's is not effective and requires surgery to correct the problem.
  • In an osteotomy, a wedge-shaped piece of bone is removed from the medial side of the femur (thigh bone). It's then inserted into the tibia to replace the broken down inner edge of the bone. Hardware such as pins and screws may be used to hold everything in place. If the fixation is used inside the leg, it's called internal fixation osteotomy. External fixation osteotomy describes a special circular wire frame on the outside of the leg with pins to hold the device in place.
  • Unfortunately, in some patients with adolescent Blount's disease, the bowed leg is shorter than the normal or unaffected side. A simple surgery to correct the angle of the deformity isn't always possible. In such cases an external fixation device is used to provide traction to lengthen the leg while gradually correcting the deformity. This operation is called a distraction osteogenesis. The frame gives the patient stability and allows for weight bearing right away.

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