Blount’s Disease: Definition, Causes, Symptoms, Diagnosis and Treatment

It is a rare growth disorder that affects children.

It is located in the medial tibial physis, characterized by an abrupt varus deformity in the proximal tibia.

Blount’s disease in children causes the legs to bend outward just below the knees and can lead to future problems with gait.

This disorder is usually identified early in gait and is not self-correcting.

Early onset is more common, usually bilateral, and is associated with heavier children who walk early.

Blount’s disease has two predominant incidence peaks, a more common childhood form (onset <5 years of age) and an adolescent form.

The infantile form usually begins as early as 1 to 3 years of age and is commonly first noticed when starting to walk, with the greatest progression seen in the first 4 years of life.

Almost all children who receive early treatment respond very well.

Anatomy

The tibia (lower leg bone) or more commonly called the shin is affected by Blount’s disease.

In the growing child, there are special structures at the end of most bones called growth plates.

The growth plate is sandwiched between two special areas of the bone called the epiphysis and metaphysis.

The growth plate is made of a special type of cartilage that builds bone on top of the end of the metaphysis and lengthens the bone as we grow.

In Blount’s disease, both the epiphysis and the metaphysis are involved and only the medial or medial border of the bone is affected.

The metaphysis is the widest part of the shaft of the tibial bone. In the early stages of Blount’s disease, the medial metaphysis ruptures and growth stops.

In the growing child, the metaphysis that contains the growth zone consists of cancellous bone that has not yet hardened.

Causes of Blount’s disease

The exact cause of Blount’s disease remains unknown.
However, scientists believe it is the combination of several contributing factors, including genetic, environmental, and mechanical.

Mechanical factors

Skeletal discharge is associated with a significant reversible adverse effect on bone. This must be taken into account when interpreting radiographs.

Obesity and gait before 1 year can exacerbate curvature deformity in soft, non-mineralized bones. Even normal bones can lean when exposed to excess weight.

Blount’s disease is a lower extremity tilt disorder that can mimic localized metaphyseal dysplasia or rickets.

Although individuals with a high body mass index develop an increase in body mineral density, this does not compensate for the increase in body weight.

Overweight teens can also develop Blount’s disease.

Nutritional and environmental factors

Several nutritional and environmental factors influence bone and mineral metabolism. Insufficient calcium, vitamin D, vitamin C, or copper can lead to physical abnormalities.

Maternal illness, nutrition, and toxic exposure can affect the skeletal health of the fetus.

Blount’s disease is more common in African Americans and more common in women in the infantile and adolescent form, and bilateral in 80% of childhood patients, but generally unilateral in the late-onset form.

Symptoms of Blount’s disease

Blount’s disease becomes evident between the ages of two and four as the tilt worsens.

In Blount’s disease, the characteristic finding is an abrupt angulation of the medial aspect of the superior tibia.

A general pattern of radiographic progression has been described. The earliest findings are medial fragmentation of the proximal tibial metaphysis, medial metaphyseal knocking, and generalized metaphyseal irregularity.

Subsequently, there will be a progressive medial metaphyseal depression resulting in varus angulation and deepening of the metaphyseal peak.

The medial epiphysis will appear sloping downward and will enlarge to fill the metaphyseal space.

In later stages, the epiphysis will appear divided into two parts. In the last stage, there is a bony fusion through the medial physis. Advanced cases can also show lateral subluxation of the tibia.

Physiologic tilt will manifest on standing radiographs as tilt of the entire lower limb measuring> 10 degrees at 18 months or more.

In adolescents (older than 11 years of age), Blount’s disease is more likely to be unilateral and affect only one leg.

Diagnosis of Blount’s disease

Blount’s disease is often first suspected when tilting of the legs in a child is observed during a normal visit to a pediatrician, who will usually refer the case to an orthopedic surgeon.

The older a child is when the condition is detected, the more obvious these changes will be on the X-ray.

Identification of Blount’s disease is done through a careful physical examination, followed by x-rays of the legs.

These x-rays will show the abnormal shape of the tibia and possibly changes in the growth plate of the bone just below the knee.

Orthopedic surgeons will take measurements from X-rays of the angles of different segments of the leg, to distinguish between normal bone growth and development and Blount’s disease, which shows a more severe tilt.

If the diagnosis of Blount’s disease is made, these measurements will allow the surgeon to create the best treatment plan and track the correction of the deformity as a result of future treatment.

Treatment of Blount’s disease

Treatment of Blount’s disease ranges from simple observation to surgery.

Observation

Decisions about the best treatment for each child depend primarily on the age of the child at diagnosis and the severity of the leg tilt.

If a slight tilt is detected in a child younger than 2 years old, the best treatment is observation, in which an orthopedic surgeon monitors the progression of the condition.

In many cases, the bow will prove to have been normal growth and development, and will correct itself within about 1 year without any further treatment by a physician.

Orthosis

However, if the tilt worsens or is found in a 2- to 4-year-old child, Blount’s disease can be treated with the use of braces placed on the child’s legs by an orthopedic surgeon.

These braces, called a knee-ankle-foot orthosis, extend from the upper thigh to the tips of the fingers.

There are several different models of braces, but the goal is the same with each of them to gradually guide the growth of the legs to a straighter position of the legs, so that the knees and feet are aligned correctly, without bending. .

Each child’s brace is designed specifically for them, requiring the creation of leg casts.

The continued development of the legs with the use of braces is then monitored by an orthopedic surgeon, through follow-up exams and x-rays.

Surgery

If the treatment is not effective and requires surgery to correct the problem.

Surgical correction may be necessary, especially for the younger child with advanced stages of tibia varum or the older child who has not improved with the brace.

Surgery is generally not done in children under the age of two because at this young age, it is still difficult to tell if the child has Blount or just excessive tibial tilt.

In an osteotomy, a wedge-shaped piece of bone is removed from the medial side of the femur (thigh bone).

It is then inserted into the tibia to replace the broken inner edge of the bone.

Tools such as pins and screws can be used to hold everything in place.

If the fixation is used inside the leg, it is called an internal fixation osteotomy.

The 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 adolescent Blount disease patients, the bowed leg is shorter than the normal or unaffected side.

Simple surgery to correct the angle of the deformity is not 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 distraction osteogenesis. The frame gives the patient stability and allows immediate weight loading.

Rehabilitation

Internal fixation osteotomy usually heals in 6 to 8 weeks.

The cast is removed five to six weeks after the operation if there is enough bone accumulation to prevent change or loss of position.

A second cast is applied that keeps the knee straight but the foot and ankle free so that the weight passes through the leg.

When the child has surgery with external fixators and distraction osteogenesis, gradual correction of the deformity takes place over the next three weeks.

After the tibia is straightened, additional rods are used to stabilize the outer frame. The frame is removed about 12 weeks after the operation.

Parents / guardians should be informed that Blount’s disease may not be cured with surgery.

Results are usually good with the Infant Warm Wand. When it is treated at a young age and at an early stage, the problem usually does not return.

Older patients with advanced deformity have a much higher risk of deformity recurrence.

Patients must be carefully followed throughout their growth and development.

The one-sided bend can make that leg shorter than the other leg. This is known as a leg length discrepancy and may need additional treatment.