Biomechanical evaluation in osteoporosis: ovariectomized rat model

The aim of our study was to investigate the effects of ovariectomy on rat femur biomechanical parameters. Bone mineral density (BMD) and histological investigation were also evaluated. Fourteen female Sprague-Dawley rats (seven ovariectomized, seven control) were used. BMD was measured by dual-energy X-ray absorbsiometry. Bone biomechanical parameters were measured in femoral midshaft with tensile test using a biomaterial testing machine and maximum load, stiffness, energy absorption capacity (structural properties), ultimate stress, ultimate strain, and elastic modulus (material properties) were calculated. Diaphyseal cortical bone thickness was measured by using histological method. The ovariectomized (OVX) rat femur's BMD was 14% lower than control rats (p=0.006). Mean maximum load was 55% less than the control group's (p=0.0001). Stiffness was 72% less in OVX rats (p=0.05). Femurs of rats with OVX had 32% less absorbed energy than controls (p=0.09). From the stress-strain curve ultimate stress, ultimate strain and elastic modulus was calculated. Elastic modulus was 53% less than controls (p=0.05). Ultimate stress decreased 21% in OVX rats (p=0.097). Ultimate strain was 25% less than controls in OVX rats. Cortical thickness was significantly decreased in OVX rats than in controls (p<0.05). In conclusion, femur biomechanical parameters are decreased in osteoporosis.