APPLICATION OF LOW-INTENSITY ULTRASOUND TO GROWING BONE IN RATS

Low-intensity pulsed ultrasound recently has been shown to accelerate long bone fracture healing, but its effect on bone growth and developm ent is unknown. The longitudinal growth and bone density of the femur and tibia in young rats was measured after application of an ultrasoun d transducer emitting 1.5-MHz pulsed ultrasound (30 mW/cm(2), SATA) fo r 20 min/day. After 28 days, no length difference was detected (less t han or equal to 2%) compared to the sham-treated leg or to unexposed c ontrols. Also, no significant difference in bone mineral density (BMD) of the femur or tibia was found (less than or equal to 6%). In a repe ated experiment in which a periosteal trauma stimulus was created in t he femoral diaphysis, the ultrasound also had no effect on growth or B MD, This result suggests that physeal bone growth is far less sensitiv e to this level of ultrasound application than is fracture repair. Thi s may be related to the cascade of cellular events and regulatory fact ors that are present after a fracture. (C) 1998 World Federation for U ltrasound in Medicine & Biology.