Effect of 4 Hz and multifrequency pulsed electromagnetic field (PEMF) on bone fracture healing

Pulsed electromagnetic fields (PEMF) have been used in bone fracture healing for many years. However, it is still not clear which frequencies are more effective. Therefore, the aim of this study was to investigate the effect of single frequency of 4 Hz and a package of multiple frequencies (220 Hz, 727 Hz, 880 Hz and 10 kHz) on bone fractures of rats. Rats were randomly divided into three groups: sham, R4 and RM. A transverse osteotomy was created in the right medial tibias diaphysis of each rat under anesthesia. The right tibia of the rats in the R4 and RM groups was exposed to 4 Hz, and a package of multiple frequencies, respectively. The rats in both irradiation groups were exposed to a pulsed magnetic field with an amplitude of 10 mT for 1 h/day during 1 month under anesthesia with ketamine (90 mg/kg, i.p.) and xylazine hydrochloride (9 mg/kg, i.p.). The rats in the sham group were kept under the same experimental conditions without any field exposure. At the end of the study, the right tibia of each rat was removed and bone healing was evaluated histopathologically and radiologically, and the concentrations of some elements were measured, such as Na, Mg, K, Cr, Mn, Fe, Zn, Se, Ca and P. The results showed that 4 Hz exposure was more effective in bone fracture healing than the other frequencies in this study. Further studies need to be conducted to determine the mechanisms underlying the effect of 4 Hz PEMF.