The lower part of the human leg extends from the knee to the ankle. It is informally called the shank of the leg. The tibia is the second-largest and strongest bone present in the front of the shank. The tibia is known as the shank bone or shin bone. The upper portion of the tibia articulates at the knee joint, and the lower portion articulates at the ankle joint. The tibia is classified as a long bone and divided into three regions.
Epiphysis - Ends of the long bone.
Metaphysis - Portion of a long bone between the epiphysis and the diaphysis.
Diaphysis - Mid-section of a long bone.
What Is Blount’s Disease?
Blount’s disease is a disorder of the tibia bone. It is characterized by a bend in the shank region, which causes the lower leg to angle inward. It resembles a bowed leg. Blount’s disease usually affects children and adolescents. Children of Hispanics and Afro-Americans are more frequently affected than others.
Erlacher was the first scientist to describe this condition in 1922, but the article written by surgeon Walter Blount in 1937 prompted the diagnosis of Blount’s disease. Blount’s disease is also known as,
What Are the Types of Blount’s Disease?
Based on age, Blount's disease is classified as:
The infantile form is more common in girls, and the adolescent form is common in boys.
The following are the differences in both types of Blount’s disease.
What Causes Blount’s Disease?
The exact cause of Blount's disease is unknown. It is a developmental disorder characterized by disturbance in the orderly sequence of bone formation from cartilage at the upper end of the tibia. Thus the growth plate (active area of bone growth) of the bone is affected. Some of the causative factors are:
Infection of bone spreads from the bloodstream or nearby tissues.
Trauma or injury.
Osteonecrosis (bone death due to loss of blood supply).
Vitamin D deficiency.
Developmental abnormalities in the skeleton.
Blount’s disease has a multifactorial origin. Research also suggests a relationship between early walking and obesity to Blount’s disease. Excess load and genetics have also been attributed.
Certain children below the age of two years may have a bowed leg appearance, which seems to be a normal variation in leg position. This biological variation is called physiology genu varum. The condition improves after two years, and the leg becomes normal as the age advances.
What Are the Symptoms of Blount’s Disease?
The deformity is more evident.
Turning in of the feet.
Awkward walking pattern.
The bone spike at the knee joint.
Discomfort in the hip, knee, and ankle region.
How to Diagnose Blount’s Disease?
Physical examination and imaging techniques are used to diagnose Blount’s disease. Through physical examination, physicians may examine the extent and symmetry of the condition in both legs.
X-Rays: The angle of the deformity can be analyzed through X-rays. Any deviation in the angle (tibiofemoral angle) between the axis of the femur (thigh bone) and the axis of the tibia (shank bone) indicates Blount’s disease.
MRI (Magnetic Resonance Imaging): Abnormal thickness, height, and width can be assessed with MRI. Cartilage tears can also be seen.
What Are the Stages of Blount’s Disease?
Staging is done only for the infantile form. Langenskiold classified Blount’s disease into six stages depending on the severity and collapse of the bone ends. The stages are classified based on the radiographic evaluation.
Stage I: Irregular metaphyseal breaking.
Stage II: Saucer-shaped defect in the medial metaphysis.
Stage III: Saucer deepens into a step deformity.
Stage IV: The epiphysis slopes over the metaphysis break.
Stage V: Double epiphysis.
Stage VI: Bony bridge at the physis region.
How to Treat Blount’s Disease?
The treatment is selected based on the age and severity of Blount's disease.
KAFO (Knee Ankle Foot Orthosis): In infantile Blount’s disease, KAFO bracing can be used for children below three years of age. Pediatric KAFO offers non-surgical treatment for Blount’s disease. A unique KAFO can be custom fabricated for young patients. It is recommended to wear KAFO for 23 hours per day.
Graded Growth: Growth modulation can be done to allow the growth of the metaphysis to catch up with the regular growth, thus correcting the deformity. Plates and staples are used for growth modulation.
External Fixators: Currently, external fixators (Taylor spatial frame or Llizarov ring) are used in the correction of Blount’s disease.
Surgery: Tibial osteotomy (reshaping) is the recommended surgery for Blount’s disease. Realignment osteotomy is done in children under the age of four. A variety of fixation devices like cast, pins, screws, bars, and plates are used.
Postoperatively, the joint should be kept weight limited, and crutches are used for six to eight weeks for walking. Casting is done to limit the movements. The cast should be changed at four weeks and worn for eight weeks till the union is evident in X-rays. If external fixators are used after surgery, they should be kept in place for twelve weeks.
Continuing follow-up care after initial surgical correction is necessary because of the risk of recurrence.
The incidence of Blount’s disease is on the rise as the obesity rates in children are higher. Young children with stage I to stage IV can have spontaneous regression. In severe cases, there may be chronic joint pain that limits physical activity. The best treatment outcome can be achieved with early diagnosis and unloading the joint immediately with bracing or osteotomy. Parents should be educated regarding the condition, and the proper fit of the braces should be checked periodically.