A novel biomechanical testing protocol for osteoporosis in rats: femur metaphysis bending test

Objective To establish a new biomechanical test for evaluating biomechanical properties of femoral metaphysis in ovariectomized rats.Methods Twenty-five-month-old female Sprague-Dawley rats were randomly divided into ovariectomized (OVX) group and the sham-operated (Sham) group (n=10).Twelve weeks after operation,femur BMD and histomorphometry of distal femur were detected.Furthermore,femur biomechanical parameters were determined by diaphysis three-point bending test and a new designed metaphysis bending test.The relationships between the biomechanical parameters and BMD or bone histomorphometry were assessed with Pearson correlations.Results The femur BMD,bone histomorphometrical indexes (％Th.Ar,Tb.N,Tb.Th),and biomechanical parameters (maximum load,yield load and stiffness) of OVX group significantly decreased compared with Sham group.In metaphysis bending test,the mean difference of the maximum load (Fmax),yield load (Fy) between group OVX and Sham were significant higher than that in diaphysis three-point bending test.Positive correlations between biomechanical parameters and femur BMD or bone histomorphometry indexes were observed in both the diaphysis bending and metaphysis bending test.The biomechanical parameters in the metaphysis bending test showed stronger correlations with BMD and bone.Conclusion Femur metaphysis bending test could be used to evaluate the biomechanical properties of osteoporosis.When compared with diaphysis bending test,femur metaphysis bending test is more sensitive in evaluating the change of biomechanical properties of femur in osteoporotic rats. Key words: Osteoporosis;  Rats;  Femur; , Biomechanics