Pediatric reference data for dual X-ray absorptiometric measures of normal bone density in the distal femur

Many children at risk for osteoporosis have substantial hip and knee contractures that prevent assessment of bone mineral density in the "usual" region, the proximal femur. As an alternative, bone density may be measured in the distal femur projected in the lateral plane. The purpose of this study was to provide normative reference data useful for interpretation of bone density measures in the distal femur of children and adolescents.

The study was a cross-sectional, single-observational assessment of 256 healthy children and adolescents between the ages of 3 years and 18 years 6 months (mean, 10 years 5 months). Bone mineral density was measured in the nondominant proximal femur, lumbar spine, and both distal femurs using dual X-ray absorptiometry.

We found that bone mineral density increases with age in the cortical, cancellous, and mixed regions of the distal femur, similar to the findings with other regional analyses of bone density. Bone density in the distal femur correlates very highly with bone density in the proximal femur and slightly less well with bone density in the lumbar spine.

In pediatric patients who have deformities, have experienced trauma, or have undergone surgical procedures that prevent reliable measures of bone density in the proximal femur, bone mineral density may be measured in the distal femur and interpreted relative to the bone mineral density findings in healthy age- and sex-matched controls.