BaiLing Chen, YiQiang Li, XiaoXi Yang and DengHui Xie
The diaphysis bending test is generally accepted to assess the biomechanical properties of bone in osteoporotic animals. However, bone strength loss was more pronounced at the metaphysis than diaphysis. Therefore, the biomechanical test should be focused on the metaphysis. This study aimed to validate a novel biomechanical test for femoral metaphysis in ovariectomized rats. Twenty 5-month-old female Sprague-Dawley rats were randomly divided into the ovariectomized (OVX) and sham-operated (Sham) groups. Examination of femur bone mineral density (BMD) and histomorphometry of the distal femur were performed. Femur biomechanical parameters (maximal load, yield load, and stiffness) were determined by the diaphysis bending test and a novel designed metaphysis bending test. Pearson's correlations were used to analyze the relationships between the biomechanical parameters and BMD or bone histomorphometry indexes (%Tb.Ar, Tb.N, Tb.Th), respectively. The femur BMD, bone histomorphometry indexes, and biomechanical parameters of OVX were inferior to those of the Sham group (P < 0.05). In the diaphysis bending test, the mean difference of the maximum load and yield load between the OVX and Sham groups were 13.83 ± 5.27 and 15.69 ± 4.15 N, which were significantly lower than in the metaphysis bending test (43.34 ± 4.27, 48.90 ± 4.35 N; all P < 0.05). 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 histomorphometry indexes. The femoral metaphysis bending test was validated to assess osteoporosis in our study, and it was more sensitive than the diaphysis bending test in evaluating the change of biomechanical properties of the femur in osteoporotic rats.