Mechanobiology of femoral neck structure during adolescence.

Understanding femoral neck structure may be critical to preventing fractures at this site. We examined the correlates of changes in the femoral neck during adolescence. Dual energy x-ray absorptiometry measurements of proximal femora were made in 101 Caucasian youths (ages 9 to 26 years). Relationships were examined between developmental parameters (age, pubertal stage, height, body mass, lean mass, and fat mass) and femoral structure (bone mineral content, bone mineral density, neck width, cross-sectional area, and cross-sectional strength). Lean body mass was the best predictor of femoral neck structure, explaining 53-87 percent of the variance, and was independent of gender. Body mass only explained 51-79 percent of the variance. Previously we found body mass to be the strongest predictor of femoral mid-diaphyseal cross-sectional properties. These findings suggest that trabecular bone of the femoral neck may be more responsive to its mechanical environment than the cortical diaphysis. In addition, lean body mass may be a more reliable predictor of muscle loading than body mass.