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Measuring All Angles of Early Versus Late Blount Disease

Blount disease looks like bowlegs. Bow legs is also known as tibia varum (singular) or tibia vara (plural) Most toddlers and young children with bow legs grow out of it. Those who don't may have pathologic tibia varum or Blount disease.

In this study, children who developed Blount disease early (by age two) were compared to children with late onset (around age 10). X-rays were used to measure the angles of the lower leg bones from the front and from the side. This is called multiplanar analysis.

The curve of the bone viewed from the front of the tibia(lower leg bone) is called varum. The curve of the bone viewed from the side is called procurvatum. And any rotation or twist of the bone is called tibial torsion. All three of these changes were measured and compared between a group of children with early-onset versus late-onset Blount disease.

They found that patients with early-onset Blount disease had greater severity and worse deformity. The older patients were more likely to have changes in the lower part of the femur (upper leg bone). Deformity in younger children was mostly caused by changes in the tibia.

The authors suggest measuring all angles of both the lower femur and upper tibia is important in Blount disease. The goal of treatment is to line the bones up as normally as possible. It's important to keep equal leg lengths until the child has stopped growing.

Having multiplanar analysis of deformities can help the surgeon avoid overcorrecting or undercorrecting the problem. The right amount of correction prevents other deformities from occurring.

References: Sanjeev Sahbharwal, MD, et al. Multiplanar Deformity Analysis of Untreated Blount Disease. In Journal of Pediatric Orthopaedics. April/May 2007. Vol. 27. No. 3. Pp. 260-265.

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