The effect of varying magnitudes of whole-body vibration on several skeletal sites in mice.

It has been reported that whole-body vibration (WBV) is anabolic to trabecular bone in animal models and humans. It is likely that this anabolic response does not occur uniformly throughout the entire body. Two factors that may affect the observed anabolic response are vibration magnitude and skeletal site of interest. In this study, mice were loaded with WBV of varying magnitudes. After five weeks of loading, bone marrow was flushed from tibias in order to quantify osteoprogenitor cells. Staining with alizarin red (an indicator of mineralization) showed a significant decrease in percent stained area in the 0.3 g loaded group compared to the control group and the 1.0 g group. MicroCT analysis was performed at five skeletal sites: the proximal tibial metaphysis, femoral condyles, distal femoral metaphysis, proximal femur, and L5 vertebral body. Increasing magnitudes of WBV were associated with a non-dose-dependent increase in trabecular bone volume (BV/TV) at the proximal tibial metaphysis, although other sites were unresponsive. There were statistically significant increases in BV/TV in the 0.1 g group (32% increase) and 1.0 g group (43% increase) compared to control (p < 0.05). The 0.1 g and 1.0 g groups also had higher BV/TV than the 0.3 g loaded group. If this non-dose-dependent phenomenon is verified by future studies, it suggests that a range of magnitudes should be examined for each application of WBV.