Pulsed electromagnetic field therapy can be used to treat osteoporosis

Abstract

Objective To observe the effect of a pulsed electromagnetic field (PEMF) on the bone structure and metabolism of rats with disuse osteoporosis (DOP). Methods One hundred 4-month-old female Sprague-Dawley rats were randomly divided into a control group (INT group), an osteoporosis model group (DOP group), a sodium alendronate group (ALN group) and a pulsed electromagnetic field group (PEMF group), each of 25. The right hind-limbs of the rats in the DOP, ALN and PEMF groups were immobilized by tibia-tail fixation for two weeks to establish a DOP model. The rats in the ALN group were given 1 mg/kg of sodium alendronate once a day, while those in the PEMF group received PEMF at 3.82 mT and 10 Hz with a pulse time of 8 ms for 40 min/d. Five rats in each group were sacrificed at the 2nd, 4th, 8th and 12th week and their right hind-limbs were separated to measure the bone mineral density (BMD), structural mechanics indexes (the maximum load, maximum displacement and rupture energy) and material mechanics indexes (maximum stress, maximum strain and modulus). Moreover, the expression of tumor necrosis factor alpha (TNF-α) and bone morphogenetic protein 2 (BMP-2) were detected using immunohistochemical methods. Results The average BMD of the model group was significantly lower than that of the ALN group after 2 weeks, and lower than that of the PEMF group after 4 and 8 weeks. After 12 weeks the average BMD of the PEMF group was significantly higher than that of the ALN and model groups. After two and four weeks, all the structural and material mechanics measurements had decreased significantly compared with those of the control group. The average maximum displacement and load of the ALN group had increased significantly compared with the model group after 4 weeks of treatment. After 8 weeks the average maximum load, maximum displacement, rupture energy and maximum stress of the ALN and PEMF groups had increased significantly compared with the model group. Compared with the model group, the average level of TNF-α decreased gradually in both the ALN and PEMF groups from the 2nd week on, while that of BMP-2 increased from the same time point. However, at the 8th week the expression of BMP-2 protein in the PEMF group was on average significantly higher than in the ALN group. Conclusion Both PEMF and sodium alendronate can increase bone density, but PEMF has more persistent effects. Key words: Pulsed electromagnetic fields; Osteoporosis; Bone mineral density; Bone biomechanics