Fracture healing is impaired in osteoporotic bone. Low-magnitude high-frequency vibration (LMHFV) has recently been proven to be osteogenic in osteoporotic intact bone. Our previous study found that LMHFV significantly enhanced fracture healing in adult rats. This study was designed to explore whether LMHFV was able to promote fracture healing in osteoporotic bone by enhancing callus formation, remodeling, and mineralization and to compare with age-matched nonosteoporotic ones. Nine-month-old ovariectomy (OVX)-induced osteoporotic rats were randomized into control (OVX-C) or vibration group (OVX-V); age-matched sham-operated rats were assigned into control (Sham-C) or vibration group (Sham-V). LMHFV (35 Hz, 0.3 g) was given 20 min/day and 5days/week to the treatment groups, while sham treatment was given to the control groups. Weekly radiographs and endpoint micro-CT, histomorphometry, and mechanical properties were evaluated at 2, 4, and 8 weeks post-treatment. Results confirmed that the fracture healing in OVX-C was significantly inferior to that in Sham-C. LMHFV was shown to be effective in promoting the fracture healing in OVX group in all measured parameters, particularly in the early phases of healing, with the outcomes comparable to that of age-matched normal fracture healing. Callus formation, mineralization and remodeling were enhanced by 25-30%, with a 70% increase in energy to failure than OVX-C. However, Sham-V was found to have lesser fracture healing enhancement, with significant increase in callus area only on week 2 and 3 than Sham-C, suggesting non-OVX aged bones were less sensitive to mechanical loading. The findings of this study provide a good basis to suggest that proceeding to clinical trials is the next step to evaluate the efficacy of LMHFV on osteoporotic fracture healing.
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