It’s a fact that more and more children, pre-teens, and teens are obese and developing diabetes early in life. But diabetes isn’t the only problem overweight adolescents face. Blount disease (severe bowlegged deformity) is another possible adverse effect of obesity. And it can lead to growth arrest at the knees, leg length differences, and early degenerative arthritis.
According to Dr. J. G. Birch from Texas Scottish Rite Hospital for Children, there are actually three distinct forms of Blount disease (infantile, adolescent, and juvenile). Dr. Birch provided a review article of Blount Disease presenting information on all three types. Cause, clinical features, natural history, and treatment (conservative and surgical) are discussed for each type.
The infantile form appears between ages two and five (boys are affected more often than girls). This type can be (but is not always) related to obesity. In fact, the cause of infantile Blount disease is still a mystery.
All of a sudden, growth at the proximal end of the tibia (upper portion of the lower leg at the knee) slows down or even stops. This change in growth is referred to as physeal arrest). Along with physeal arrest comes a curving (bowing) or varus deformity and internal rotation (“torsion”) of the tibia.
The child doesn’t usually complain of pain. The deformity is obvious and the way the child walks tips the parents (or pediatrician) that something is wrong. X-rays help the physician make an accurate diagnosis. About half of the children have Blount disease on both sides with an equal number only affected in one leg. The femur (thigh bone) does not have similar deformities but it will change over time to accommodate changes in the tibia if the Blount disease is severe.
Treatment for infantile Blount disease is on a continuum from wait-and-see (sometimes the problem corrects itself) to conservative (nonoperative) care using braces and finally, surgery to correct the deformity. Dr. Birch presents a full description and discussion of the various types of surgeries that can be done, when surgery should be considered, and expected outcomes.
In the case of adolescent Blount disease, as the name suggests, the condition develops later during the teen years. It is more likely to be linked with obesity and presents differently than infantile Blount, so that treatment is different as well. The growth disturbance is not as much but the deformity can be more severe if the changes affect the femur as well as the tibia. The distal (bottom end) of the tibia may become deformed, too. Adolescents who develop Blount disease are usually treated surgically as the condition does not resolve or correct itself and bracing is not effective.
The juvenile form of Blount disease is a bit more controversial. It is really a variation of Blount disease that fits in-between the infantile and adolescent forms. Many experts don’t even make this distinction, instead only using the infantile or adolescent forms to describe the child’s condition.
Juvenile Blount disease occurs between the ages of four and 10 years. It presents a little like the infantile form of Blount disease (growth disturbance) and a little like the adolescent form (later age with more involvement of the femur). There is a need to rule out other bone diseases such as metabolic bone disease and skeletal dysplasias until the differential diagnosis can be clearly established as juvenile Blount disease.
Treatment is usually surgical since these children are older and larger (compared with children who have infantile Blount disease). The author reports that his surgical approach is similar to the one used for adolescent Blount disease (e.g., growth modulation, gradual correction of the deformity, high tibial osteotomy with hardware fixation).
Growth modulation refers to the use of small tension band plates and screws to guide growth and correction of the deformity. The most common surgical procedure done (before permanent damage occurs) is called a tibial osteotomy.
In an osteotomy, a wedge-shaped piece of bone is removed from the medial (inner) 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. For more details on treatment, see our publication A Patient’s Guide to Blount’s Disease in Children and Adolescents.
In summary, this review article covers all aspects of clinical presentation, differential diagnosis, and management of Blount disease in its various forms. Dr. Birch provides a detailed discussion of each content area along with X-rays and photographs demonstrating treatment techniques. Before and after results of surgery are also included.
He suggests treating infantile Blount disease when deformity is asymmetric (different from one side to the other) or if the problem persists after age 18 months. Bracing can be used effectively for children up to age three. Older children or children who do not respond to the bracing are candidates for surgical correction. Recurrence of the condition and/or irreversible growth disturbance are two problems that create a challenge to successful treatment.