Preliminary studies of duration and intensity of ultrasonic treatments on fracture repair.

Bone formation of fractured fibulae stimulated by ultrasound was evaluated with roentgenography and fluorochromes labelling. The fibulae of male New Zealand rabbits were fractured to create a 3 mm-gap. Ultrasounds at 0.5 or 1.0 W/cm2 were applied for various durations, 5, 15, and 25 min/day for 4 weeks. Ultrasonic treatments at 0.5 W/cm2, 1.5 MHz significantly accelerated bone formation at the fracture site for all durations, whereas the higher intensity at 1.0 W/cm2 suppressed the bone formation of the treated fractured fibula. Ultrasounds at 0.5 W/cm2 were stimulatory to fracture repair, if given for 15 min/day, and were recommended for future clinical trials. However, ultrasounds at the intensity of 1.0 W/cm2 were deleterious to the treated fracture and not recommended for clinical trials.