ENHANCEMENT OF FRACTURE-HEALING BY LOW-INTENSITY ULTRASOUND

Fracture healing is a highly complex regenerative process that is esse ntially a replay of developmental events. These events include the act ion of many different cell types, a myriad of proteins, and active gen e expression that in the majority of cases ultimately will restore the bone's natural integrity. Several biologic and biophysical approaches have been introduced to minimize delayed healing and nonunions, some with promising results. One example of such an approach is low intensi ty pulsed ultrasound, a noninvasive form of mechanical energy transmit ted transcutaneously as high frequency acoustical pressure waves in bi ologic organisms. Numerous in vivo animal studies and perspective doub le blind placebo controlled clinical trials have shown that low intens ity ultrasound is capable of accelerating and augmenting the healing o f fresh fractures, Preliminary evidence suggests efficacy in the treat ment of delayed healing and nonunions as well, This article reviews th e animal and clinical studies that consider the effects of ultrasound on fracture healing, and the in vivo and in vitro work that strives to identify the biologic mechanism(s) responsible for the ultrasound ind uced enhancement of osteogenesis and fracture healing.