Longitudinal effects of low-intensity pulsed ultrasound on osteoporosis and osteoporotic bone defect in ovariectomized rats

Low-intensity pulsed ultrasound (LIPUS) with an intensity (spatial average temporal average, ISATA) of 30 mW/cm(2) has been widely proved to be effective on impaired bone healing, but showing little effectiveness in the treatment of osteoporosis. We hypothesized that the intensity of LIPUS may be a key factor in explaining this difference, thus two intensity levels, the widely used 30 mW/cm2 and a higher 150 mW/cm(2), were used to simultaneously treat osteoporosis and osteoporotic bone defect in ovariectomized (OVX) rats with a 1-mm drill hole on their left femurs. Results showed that 150 mW/cm(2) LIPUS augmented the healing rate of the drill hole than 30 mW/cm(2) after 3-week LIPUS treatment, although did not further enhance the healing rate after 6-week LIPUS treatment. For ameliorating osteoporosis, 150 mW/cm(2y) LIPUS achieved more advantages over 30 mW/cm(2) in improving bone density, microstructure and biomechanics 6 weeks after LIPUS intervention. In conclusion, LIPUS with an intensity of 30 mW/cm(2) was sufficient to facilitate bone defect healing, but a higher intensity can be considered as a rapid trigger for osteoporotic bone repair. In addition, improving the intensity of LIPUS may be a potentially effective consideration for alleviation of osteoporosis, and the LIPUS regimen in the treatment of osteoporosis remains to be optimized.

Automated summary

The study used two intensity levels of LIPUS, 30 mW/cm² and 150 mW/cm², to treat osteoporosis and osteoporotic bone defect in OVX rats. Results showed that 150 mW/cm² LIPUS led to faster healing of the bone defect compared to 30 mW/cm² after 3 weeks, but did not further enhance healing after 6 weeks. Additionally, 150 mW/cm² LIPUS had more advantages in improving bone density, microstructure, and biomechanics for osteoporosis compared to 30 mW/cm² after 6 weeks.