Effect of low-frequency pulsed electromagnetic field combined with whole-body vibration on bone density and mechanics performance of disuse osteoporosis rats

Objective To discuss the effect of low-frequency pulsed electromagnetic field (ELF-PEMFs) combined with-whole-body vibration(WBV) on the bone mineral density, bone microstructure and the biological mechanics performance in-hindlimb unloading osteoporosis rats. Methods Forty female 4 months aged SD rats were randomly divided into five groups: blank group, control group, ELF-PEMFs group, WBV group, low-frequency pulsed electromagnetic field combined with wholebody-vibration(ELF-PEMFs+ WBV) group. The blank group was the normal control which comprise the healthy rats. The controlgroup was the disused osteoporosis model. Except for the blank group, thehind limb unloading rats were kept for six weeks. No intervention were provided to the blank group and the control group, other three groups were treated with physical therapy. The bodyweight of rats in each group was record. Bone mineral density was measured by Dual energy X-ray absorptiometry. The right femurs was analyzed by Micro-CT and the left femur was tested through a biomechanical machine. Results After 8 weeks of continuous treatment, the ELF-PEMFs group, WBV group, ELF-PEMFs+WBV group were significantly increased in weight and bonedensity (PELF-PEMFs=0.015, PWBV=0.016, PELF-PEMFs+WBV=0.007), (tELF-PEMFs=5.956, PELF-PEMFs=0.000; tWBV=6.127, PWBV=0.000; tELF-PEMFs+WBV=4.639, PELF-PEMFs+WBV=0.000). The difference was statistically significant (F=0.091, P=0.018). The ELF-PEMFs+WBV group was significantly higher in bone formation index. The items of BV/TV, Tb.N, Tb.Th and SMI in Micro-CT analysis increased, while Tb.Sp and Conn.D index decreased significantly. Trabecular bone structure of all the three groups was improved, however the ELF PEMFs+WBV group was better than the other two groups (vs. ELF-PEMF group, PBV/TV=0.041, PTb.N=0.026, PTb.Th=0.009, PConn.D=0.030, PTb.Sp=0.045, PSMI=0.032; vs. WBV group, PBV/TV=0.018, PTb.N=0.004, PTb.Th=0.022, PConn.D=0.042, PTb.Sp=0.039, PSMI=0.049). The maximum load, energy absorption and bone stiffness index in biomechanicalperformance test were improved. The combination treatment group were significantly improved (F=0.167, P=0.038). Conclusion Low-frequencypulsed electromagnetic field combined with whole body vibration therapy can improve bone mineral density, bone microstructureand the biological mechanics performance. They have synergistic effect and the combination therapy is better than single treatment. Key words: Osteoporosis; Electromagnetic field; Vibration; Bone density; Biomechanics