1.8 mT不同频率正弦电磁场对青年大鼠骨生物力学性能的影响

目的：研究1.8 mT不同频率的正弦交变电磁场对青年大鼠骨密度和骨生物力学性能的影响。方法：32只6周龄雌性SD大鼠随机分为对照组、10 Hz组、25 Hz组和40 Hz组，每组8只。除对照组外，均每日给予1.8 mT不同频率的正弦电磁场干预，干预时间均为90 min。干预后第4、8周经双能X线骨密度仪检测全身骨密度，并在第8周骨密度检测之后处死实验大鼠，分离骨组织，检测股骨与腰椎骨的骨密度，测量股骨长度、直径、内外两髁外侧间距，用电子万能材料试验机检测股骨和腰椎骨的生物力学指标，显微CT分析胫骨松质骨的骨微结构改变。结果：与对照组比较，10 Hz组、40 Hz组大鼠的全身骨密度、股骨骨密度、股骨最大载荷、屈服强度以及腰椎骨最大载荷、弹性模量差异均有统计学意义（均P<0.05）；而股骨的长度、直径、两髁间的宽度与对照组比较差异均无统计学意义（均P>0.05）。显微CT分析结果显示，10 Hz组、40 Hz组大鼠胫骨松质骨的骨小梁数量、分离度、骨体积百分比较对照组均增加（均P<0.01）。25 Hz组全身骨密度及股骨生物力学性能与对照组差异无统计学意义（均P>0.05）。结论：10、40 Hz的1.8 mT正弦交变电磁场可提高青年大鼠骨密度、改善骨微结构和骨生物力学特性。
Abstract: Objective: To study the effects of 1.8 mT sinusoidal electromagnetic fields of different frequencies on bone mineral density (BMD) and biomechanical properties in young rats. Methods: A total of 32 female SD rats (6-week-old) were randomly divided into 4 groups (8 in each):control group, 10 Hz group, 25 Hz group and 40 Hz group. The experimental groups were given 1.8 mT sinusoidal electromagnetic field intervention 90 min per day. The whole body BMD of rats was detected with dual-energy X-ray absorptiometry after 4 and 8 weeks of intervention. After 8 weeks of intervention, all rats were sacrificed, and the BMD of femur and lumbar vertebra, the length and diameter of femur, the width between medial and lateral malleolus were measured. Electronic universal material testing machine was used to obtain biomechanical properties of femur and lumbar vertebra, and micro CT scan was performed to observe micro structures of tibial cancellous bone. Results: Compared with the control group, rats in 10 Hz and 40 Hz groups had higher whole body BMD, BMD of femur, maximum load and yield strength of femur, as well as maximum load and elastic modulus of lumbar vertebra (all P<0.05). But no significant differences in the length and diameter of femur, and the width between medial and lateral malleolus were observed between control group and experimental groups (all P>0.05). Micro CT scan showed that the trabecular number and separation degree, bone volume percentage were significantly increased in 10 Hz and 40 Hz groups (all P<0.01). Rats in 25 Hz group also had higher BMD and better in biomechanical properties than control group, but the differences were not statistically significant (all P>0.05). Conclusion: 10 and 40 Hz of 1.8 mT sinusoidal electromagnetic field can significantly improve the bone density, microstructure and biomechanical properties in young rats. Key words: Rats, Sprague-Dawley Electromagnetic fields Tibia Bone density Osteoporosis/pathology Biomechanics