Fracture-healing is a specialized type of woundhealing response in which the regeneration of bone leads to a restoration of skeletal integrity. While the process of fracture-healing is usually considered to be biologically optimum. the healing of 5 to 10 pen cent of the estimated 5.6 million fractures occurring annually in the United States is delayed or impaired”. The cause of the impaired healing is often unknown. However, problems with operative and non-operative interventions. such as inadequate mobilization of the fracture, distraction of fracture fragments by fixation devices or traction, repeated manipulations or excessive early motion of a fracture, or excessive peniosteal stripping and damage to other soft tissues during operative exposure, intenfene with healing and may cause a delayed union or a non-union. A delayed union on a non-union may also occur if a fracture becomes contaminated at the time of the injury or after an operation or if an acceptable apposition of the fracture fragments on stable fixation is not achieved25. Moreover. specific pants of the skeleton, such as the neck of the talus. the neck of the femur, and the campal scaphoid5, are known to be at increased risk for impaired fracture-healing. and there may be problems related to peculiarities of the local blood supply or difficulties with the control of the mechanical strain environment at these sites. Thus. while most fractures heal without problems. there are several conditions unden which enhancement of the repair process would be of great benefit to ensure the rapid restoration of skeletal function. The ability of injured patients to return to the work force or to recreational activities early would not only have a substantial economic impact on society but would also improve the oven-all physical and mental well-being of the patients.

In this article, I will review some of the better descnibed and more extensively tested methods that have been used to stimulate fracture-healing. I will also provide an introduction to certain new technologies that could improve the repair of fractures. The article is organized in two sections. The first section is a discussion