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Osteoporosis is a common degenerative bone disease that results in bone loss and fracture in the elderly and to people of any age with disabilities. Current drug treatments only provide either increased bone formation or decreased bone resorption, and can cause adverse effects. As an alternative to drugs, low intensity vibration (LIV) may improve skeletal health without potential side effects from drugs. LIV has been shown to increase bone health short term in both animal and clinical studies. Long term benefits from LIV are currently unknown, so the objective of this research was to investigate the long-term effects of whole body vibration therapy on bone morphology, bone mineral density (BMD), mechanical properties, and histological bone formation. In this study, 10-week old female mice were given LIV for 8 weeks; while a control group received a SHAM treatment i.e. no vibration. Two sets of groups remained on study for an additional 8 or 16 weeks post treatment (N=17). Femoral dynamic loss stiffness (K”) significantly increased by 18% after 8-weeks of LIV compared to SHAM. Damping, tan delta, and loss stiffness, significantly increased by 18%, 16%, and 17% respectively at 8 weeks LIV compared to SHAM. Finite element models of applied LIV signal showed decreased stress in the mid- diaphyseal region at both 8-week LIV and 8-week post treatment compared to SHAM. Residual mechanical changes in bone during and post-LIV indicates that LIV could be used to increase mechanical integrity of bone. Epiphyseal trabecular mineralizing surface to bone surface ratio (MS/BS) and bone formation rate (BFR/BS) was significantly greater in the LIV group compared to the SHAM group at 8 weeks by 92% and 128% respectively. Mineral apposition rate (MAR) was significantly greater in the LIV group 16 weeks post treatment by 14%. In the metaphyseal trabecular region at 16 weeks post treatment, MS/BS and BFR/BS was significantly greater in the LIV group by 106% and 145% respectively compared to the SHAM group. Significant positive effects of LIV were found in the trabecular µCT morphological results in all regions studied at 8 weeks post treatment, and even at 16 weeks post treatment in the metaphyseal trabecular region. BMD increased by 18%, bone volume tissue volume ratio (BV/TV) increased by 37%, and bone surface bone volume ratio (BS/BV) decreased by 14% in the LIV group compared to the SHAM group at 8 weeks post treatment. Significant effects 16 weeks post treatment were maintained with a 36% BV/TV increase and 11% BS/BV decrease. No significant LIV effects in trabecular bone were apparent using µCT immediately after 8 week treatment. Significant positive effects in the middle-cortical region included: bone volume (BV) increased by 4%, BS/BV decreased by 3%, and cortical thickness increased by 3% in the LIV group compared to the SHAM group immediately after 8 week treatment. LIV improves trabecular and cortical bone morphological parameters, BMD, histological bone formation, and dynamic stiffness compared to SHAM immediately after and in some cases long-term post LIV. Results from this work will be helpful in developing treatment strategies to increase bone health in younger individuals. |
