ABSTRACT
Objective To observe the effect of pulsed electromagnetic fields(PEMFs)of different daily treatment durations on biomechanical properties of femur in ovariectomized rats,so as to find out the optimal daily treatment time.Methods Fifty female Sprague-Dawley rats were randomly divided into five groups:(1)SHAM control(no PEMFs treatment),(2)OVX control(no PEMFs treatment),(3)OVX I(PEMFs treatment at 8Hz fre- quency with 3.8 mT intensity,20 min daily for 30 days),(4)OVX 11(PEMFs treatment at 8 Hz frequency with 3.8 mT intensity,40 min daily for 30 days),and(5)OVXⅢ(PEMFs treatment at 8Hz frequency with 3.8 mT in- tensity,60 rain daily for 30 days).All the rats were subject to bilateral overiectomy except those in the SHAM control group.The biomechanical properties of the femur were assessed after 30 days of PEMFs treatment.Results The values of the parameters of the biomechanical properties obtained with the OVX control group were significantly lower than those of the other 4 groups(P0.05).Conclusion PEMFs of the three different daily treatment durations can maintain the biomechanical properties of the femur in ovariectomized rats.Under certain in- tensity(3.8 mT)and frequency(8 Hz),PEMFs of the three different treatment durations can significantly maintain biomechanical properties of femur in ovariectomized rats approximately to the nomal level,but among the three groups,the difference is not significant.It was shown that exposure to PEMFs for 20 to 60 minutes daily had similar effect of maintaining biomechanical properties of the femur in ovariectomized rats.