Effect of abnormal mineralization on the mechanical behavior of X-linked hypophosphatemic mice femora.

The Hyp mouse is an established animal model of X-linked hypophosphatemia, one of the most common genetic forms of metabolic bone disease in humans. This study describes the first determination of whole bone mechanical behavior in the heterozygous male and female Hyp mouse. Femora from 12-week-old mice were tested in torsion. The contribution of structural and material properties to mechanical behavior was determined by geometrical evaluation prior to testing and by analysis of the diaphyseal mineral after testing. The male and female Hyp femora were found to undergo significantly more angular deformation at failure than the same sex normal femora (82.49 +/- 24.37 vs. 22.63 +/- 8.02 rad/m [corrected] for the females and 128.90 +/- 37.05 vs. 22.79 +/- 7.24 rad/m [corrected] for the males) and to have a significantly lower structural stiffness (0.373 +/- 0.130 x 10(-3) vs. 1.33 +/- 0.380 x 10(-3) [corrected] [N-m/(rad/m)] for the females and 0.167 +/- 0.104 x 10(-3) vs. 1.60 +/- 0.502 x 10(-3) [corrected] [N-m/(rad/m)] for the males). The male Hyp femora had a significantly lower failure torque than male normal femora (1.58 +/- 0.62 x 10(-2) vs. 3.44 +/- 1.57 x 10(-2) N-m). Because the polar movement of inertia, a geometrical property that affects torsional behavior, was not significantly different between the Hyp femora and the same sex normals, differences in mechanical behavior were attributed to material properties.(ABSTRACT TRUNCATED AT 250 WORDS)