Deterioration of bone quality by long-term magnetic field with extremely low frequency in rats

The aim of our study was to investigate the effects of long-term (45 days) magnetic field (50 Hz, 1 mT; MF) on femur biomechanical parameters of rats. Bone mineral density (BMD) and histological investigation were also evaluated. For this purpose, twenty-four 8-week-old, Wistar-Albino female and male rats were assigned randomly to female control (FC) and MF-exposed rats (F-MF); male control (MC) and MF-exposed rats (M-MF). BMD was measured by dual-energy X-ray absorptiometry. Cross-sectional area of the femoral shaft was evaluated by computerized tomography. Biomechanical measurements were performed at the mid-diaphysis of the left femur with tensile test. Maximum load, displacement, stiffness, energy absorption capacity (structural properties); ultimate stress, ultimate strain, elastic modulus and toughness (material properties) were calculated. Diaphysial cortical bone thickness was measured by using histological method from the right femur. In respect to the cortical thickness of the rats' femurs, there was statistically significant interaction between the gender and group (P<0.05), while the BMD and cortical area were not (P>0.05). The BMD, cortical thickness and area values of the femurs of MF-exposed rats (F-MF, M-MF) were significantly decreased in comparison to that of the controls (FC, MC) (P<0.05). There were no statistically significant differences between the control and the MF-exposed rats in respect to the femur length (P>0.05). There were no statistically significant interaction between the gender and group with regard to the maximum load, displacement, stiffness, ultimate stress, ultimate strain, elastic modulus and toughness endpoints, while the energy absorption capacity was significant (P<0.05). Maximum load, displacement and stiffness values of MF-exposed rats were significantly decreased compared to that of the controls (P<0.05). Femurs of M-MF rats had less absorbed energy than that in controls (P<0.05). Ultimate stress and elastic modulus parameters were significantly decreased in MF-exposed rats in comparison to that of the controls (P<0.05). Ultimate strain was higher in MF-exposed rats than that in controls (P>0.05). The mean of toughness was decreased in MF-exposed rats compared to that of the controls (P>0.05). In conclusion, the bone quality of rats is decreased by magnetic field exposure.