The Long-Term Residual Effects of Low-Magnitude Mechanical Stimulation on Murine Femoral Mechanics.

As an alternative to drug treatments, low-magnitude mechanical stimulation (LMMS) may improve skeletal health without potential side effects from drugs. LMMS has been shown to increase bone health short term in both animal and clinical studies. Long-term changes to the mechanical properties of bone from LMMS are currently unknown, so the objective of this research was to establish the methodology and preliminary results for investigating the long-term effects of whole body vibration therapy on the elastic and viscoelastic properties of bone. In this study, 10-week-old female BALB/cByJ mice were given LMMS (15 min/day, 5 days/week, 0.3 g, 90 Hz) for 8 weeks; SHAM did not receive LMMS. Two sets of groups remained on study for an additional 8 or 16 weeks post-LMMS (N = 17). Micro-CT and fluorochrome histomorphology of these femurs were studied and results were published by Bodnyk et al. (2020, "The Long-Term Residual Effects of Low-Magnitude Mechanical Stimulation Therapy on Skeletal Health," J. Biol. Eng., 14, Article No. 9.). Femoral quasi-static bending stiffness trended 4.2% increase in stiffness after 8 weeks of LMMS and 1.3% increase 8 weeks post-LMMS compared to SHAM. Damping, tan delta, and loss stiffness significantly increased by 17.6%, 16.3%, and 16.6%, respectively, at 8 weeks LMMS compared to SHAM. Finite element models of applied LMMS signal showed decreased stress in the mid-diaphyseal region at both 8-week LMMS and 8-week post-LMMS compared to SHAM. Residual mechanical changes in bone during and post-LMMS indicate that LMMS could be used to increase long-term mechanical integrity of bone.

The long-term residual effects of low-magnitude mechanical stimulation therapy on skeletal health.

BACKGROUND: Low-magnitude mechanical stimulation (LMMS) may improve skeletal health. The objective of this research was to investigate the long-term residual effects of LMMS on bone health. 10-week old female mice were given LMMS for 8 weeks; SHAM did not receive LMMS. Some groups remained on study for an additional 8 or 16 weeks post treatment (N = 17). RESULTS: Epiphyseal trabecular mineralizing surface to bone surface ratio (MS/BS) and bone formation rate (BFR/BS) were significantly greater in the LMMS group compared to the SHAM group at 8 weeks by 92 and 128% respectively. Mineral apposition rate (MAR) was significantly greater in the LMMS group 16 weeks post treatment by 14%.Metaphyseal trabecular bone mineral density (BMD) increased by 18%, bone volume tissue volume ratio (BV/TV) increased by 37%, and trabecular thickness (Tb.Th.) increased by 10% with LMMS at 8 weeks post treatment. Significant effects 16 weeks post treatment were maintained for BV/TV and Tb.Th. The middle-cortical region bone volume (BV) increased by 4% and cortical thickness increased by 3% with 8-week LMMS. CONCLUSIONS: LMMS improves bone morphological parameters immediately after and in some cases long-term post LMMS. Results from this work will be helpful in developing treatment strategies to increase bone health in younger individuals.