What is Blount’s Disease?
Blount’s disease, also known as tibia vara, is a developmental growth abnormality that affects the growth plate of the shin bone (tibia), causing the lower leg to angle outwards with a bow-like appearance. Growth plates, also known as the physis or epiphyseal plate, are found at the ends of long bones in children and adolescents and help to determine the shape and length of the adult bone.
Blount’s disease can occur in one or both legs and can result in shortening of the affected leg along with other changes within the bones of the legs. It is a progressive disease that worsens with growth if not treated, and hence, early diagnosis and aggressive treatment are extremely important to thwart the progress of the disease.
Types of Blount’s Disease
Infantile Blount’s disease:
- Occurs in toddlers under the age of 4
- Abnormality is noted only in the tibia
- Usually affects both legs (bilateral)
- More common than adolescent Blount’s disease
Adolescent Blount’s disease:
- Occurs in children over 10 years of age
- Usually affects only one leg (unilateral)
- Abnormality is noted in both the femur (thigh bone) and the tibia
- Less common than infantile Blount’s disease
Causes of Blount’s Disease
In Blount’s disease, severe pressure is applied on the growth plate at the uppermost part of the tibia. The growth plate is made up of cartilage, which is weaker than the bone. The job of the growth plate is to enable bones to lengthen and grow accordingly. But application of pressure on the growth plate hinders the bone from growing naturally. Instead, the outer or lateral portion of the tibia continues to grow but the inner or medial portion of the bone does not. This causes uneven bone growth resulting in outward bending of the tibia instead of growing straight.
Risk Factors of Blount’s Disease
The exact cause of Blount’s disease is still unclear; however, physicians believe it may occur due to a combination of several risk factors, including:
- Early walking in infants
- Genetic or hereditary factors
- Family history of Blount’s disease
- Overweight or obesity
- Female sex, as it is more common in girls
- Race, as this is more prevalent in children of African heritage
- Low vitamin D levels
Signs and Symptoms of Blount’s Disease
Typical signs and symptoms of Blount’s disease include:
- Bowing of the leg under the knee
- Knee pain
- Knee instability
- In-toeing (feet angling inward instead of straight out)
- Trouble walking
- Arthritis of the knee joint
Diagnosis of Blount’s Disease
Your child’s pediatric orthopedist will conduct a physical examination of the leg to look for signs and symptoms of Blount’s disease. If the condition is suspected, your pediatric orthopedist will order an X-ray for a detailed examination of the bone deformity and abnormalities at the growth plate, which helps to confirm the diagnosis.
Treatment for Blount’s Disease
The main objective of the treatment for Blount’s disease is to rectify the bone abnormality and improve overall alignment of the legs.
- Observation: Children who are younger than 2 years are put under regular observation by your pediatrician as there is a high likelihood of children recovering naturally from bowed legs.
- Bracing: Bracing is recommended to treat Blount’s disease in children who are 2 to 4 years old and involves the use of leg braces known as KAFOs (knee-ankle-foot orthotics). The braces are created using a mold of your child’s leg and covers from the thigh to the toes. The goal of the braces is to gradually shift the curved leg bones to a straighter position over a period of time.
If braces fail to correct the bowing of the legs, then different surgical interventions can be recommended to correct the deformity, including:
- Osteotomy: This procedure involves cutting the tibia, straightening it, and fastening it with screws and plate to allow the bone to heal. This surgical method usually helps to rectify the deformity immediately.
- Hemiepiphysiodesis (Guided growth): This is a minimally invasive surgical procedure in which a tension-band plate (also known as a guided growth plate) is applied to the curved tibia to gradually straighten it as the adolescent or child grows.
- External fixator: An external fixator device such as a hexapod frame is used at the time of surgery if an osteotomy is gradually corrected. The external fixator device is placed on the outer surface of the leg and connected to the bones through the skin after they are cut. The device holds the bones in position while gradually straightening the leg.