The structural response of trabecular bone to low-level mechanical stimuli

We have previously demonstrated that low-magnitude mechanical stimuli applied at high frequencies (45 Hz) for ten minutes a day for three weeks induce an anabolic response in trabecular bone through elevated bone formation rates. In this study, we examined how a ten-week protocol involving this mechanical stimulus affected the quantity and architecture of trabecular bone. Sixteen-week adult female BALB/cByJ mice (n=8) were subjected to whole-body mechanical vibrations at 45 Hz for ten minutes, 5 days per week. After ten weeks, proximal right tibiae were harvested and scanned using a micro-computed tomography (μCT) scanner. Our analysis of bone quantity and quality revealed no significant differences in fractional bone volume, trabecular number, trabecular separation, trabecular thickness, and degree of anisotropy. There was, however, a significant increase (24%) in the structural model index, indicating transformation of the trabeculi into more rod-like structures. These data indicate that, although a structural change occurred in trabecular bone, trabecular bone volume was unaffected, possibly due to a concomitant increase in bone resorption.