Mechanical vibration applied in the absence of weight bearing suggest improved Fragile bone

Mechanical loading is critical for maintaining bone mass, while weightlessness, such as that associated with reduced physical activity in old age, long-term bed rest, or space flight, invariably leads to bone loss. Fragile bone tissue is more susceptible to fractures. By contrast, extremely low-level oscillatory accelerations, applied without constraint, can increase bone formation. To examine the role of vibration in preventing and improving the fragility of bone, we tested the effect of vibration on bone structure in a tail-suspended hindlimb-unloaded (HS) mouse model. Male 22-week-old Jcl- ICR mice were allocated randomly to the following groups: daily-standing control, HS without vibration, HS with vibration at 45 Hz (HS+45Hz), and HS with standing (as an alternative to vibration) (HS+stand). Vibration was given for 5 min/day for 4 weeks. During vibration, a group of mice was placed in a box on top of the vibrating device. The amplitude of vibration was 1.0 mm. After 4 weeks of treatment, the mice were anesthetized and killed by cervical dislocation. Trabecular bone of proximal tibial metaphyseal region of tibial diaphyseal region parameters were analyzed morphologically using in vivo micro-computed tomography. In trabecular bone, the microstructural parameters were improved in HS+45Hz group compared with HS and HS+stand group, including bone volume (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp) and trabecular bone pattern factor (TBPf). In conclusion, the results suggest a beneficial effect of vibration in preserving the complexity of trabecular bone.