Effects of vibration treatment on tibial bone of ovariectomized rats analyzed by in vivo micro‐CT

Abstract

Daily low-amplitude, high-frequency whole-body vibration (WBV) treatment can increase bone formation rates and bone volume in rodents. Its effects vary, however, with vibration characteristics and study design, and effects on 3D bone microstructure of ovariectomized animals over time have not been documented. Our goal was to determine the effects of WBV on tibial bone of ovariectomized, mature rats over time using an in vivo micro-CT scanner. Adult rats were divided into: ovariectomy (OVX) (n ¼ 8), SHAM-OVX (n ¼ 8), OVX and WBV treatment (n ¼ 7). Eight weeks after OVX, rats in the vibration group were placed on a vibrating platform for 20 min at 0.3 g and 90 Hertz. This was done 5 days a week for six weeks, twice a day. Zero, 8, 10, 12 and 14 weeks after OVX, in vivo micro-CT scans were made (vivaCT 40, Scanco Medical AG) of the proximal and diaphyseal tibia. After sacrifice, all tibiae were dissected and tested in three-point bending. In the metaphysis between 8 to 12 weeks after OVX, WBV treatment did not alter structural parameters compared to the OVX group and both groups continued to show deterioration of bone structure. In the epiphysis, structural parameters were not altered. WBV also did not affect cortical bone and its bending properties. To summarize, no substantial effects of 6 weeks of low-magnitude, high-frequency vibration treatment on tibial bone microstructure and strength in ovariectomized rats were found. Keywords: vibration; rats; ovariectomy; in vivo micro-CT Mechanical stimulation of bone by vibration has been shown in vivo to have a potential osteogenic effect, contributing to a structure more resistant to habitual loads. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] These mechanical signals are often applied in high-frequency, low-acceleration mode, and commonly result in small strains (<10 microstrain) in the bone, that are orders of magnitude lower than strains resulting from daily loads.1,7 As they are apparently harmless to the body, they may provide a potential treatment for bone-debilitating diseases like osteoporosis.In a study performed in sheep, 1 year of daily vibrations resulted in an increase of trabecular bone volume fraction of 32%. 8 In a study in which teenagers with low bone mineral density (BMD) were put on a vibration plate for 10 min a day for a year, a small increase in trabecular BMD in lumbar vertebrae was found as well as an increase in femoral cortical bone area. 13 However, in the first study on the effects of vibration in a small cohort of osteoporotic women, no significant effect on bone mineral density of the spine, hip, or distal radius was found after 1 year of treatment. 9A significant effect of treatment compliance was shown though in that study, and effects in patients of the highest quartile of compliance almost reached significance. These results thus demonstrate the potential osteogenic effect of mechanical vibration, but also suggest that the effects might be site and species dependent.To further elucidate the effects of low-magnitude, ...

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Dynamic acoustic radiation force retains bone structural and mechanical integrity in a functional disuse osteopenia model

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