1. Types
The two types of Blount's disease are infantile and adolescent. This refers to the age of onset. Before two to three years of age, infantile Blount's is practically indistinguishable from physiologic bowlegs. Normally, after 18 months of age, the knees begin to straighten out. If they don't or if the bow worsens, this is likely due to infantile Blount's disease. Blount's is formally termed tibia vara, meaning that the tibia (shinbone) itself is bowed and is the problem. The femur (thigh bone) itself is usually not affected. This is in contrast to genu varum, in which both the femur and tibia contribute to the bowing. Patients with adolescent Blount's are usually born with fairly normal alignment of their knees. However, with increased body weight and activity, the growth plate is injured. Both the infantile and adolescent forms involve a growth disturbance to the medial portion of the proximal tibia physis (growth plate of the upper shin bone). The growth of the medial side is affected, but the lateral side continues to grow normally. This causes the shinbone to become progressively more bowed.
2. Infantile Blount's Disease
Of the two forms, infantile Blount's occurs more commonly. It is usually detected by two to four years of age, when the normally straightening out of the knees does not occur. Most times, it is bilateral (both legs). The infants are usually larger for their age, and may have begun walking early, which places more stresses on the growth plate of the upper shinbone. X-rays will usually confirm the diagnosis.
3. Bracing
Wearing long leg braces while walking can correct some of the abnormal forces across the growth plate, and can help correct the deformity if they are put on early on in the disease's progression.
4. Surgery
If bracing fails to correct the deformity, then surgery is usually required. A proximal tibial osteotomy cuts the shinbone and realigns it to try to equalize the forces across the growth plate. Most times, the smaller bone in the leg (fibula) also needs to be cut. Surgery of the growth plate itself may also be required.
5. Risk Groups
Adolescent Blount's disease tends to occur in African-Americans. It occurs more commonly in males than females. As with the infantile form, higher body weight and obesity is a risk factor. Again, the theory is that there are increased forces on the medial portion of the growth plate, causing growth disturbances. By this stage, bracing is not an option and surgery is required.
Member Comments