Current trends in the enhancement of fracture healing.

Repair of fractures involves a sequence of dynamic events which ultimately restores the integrity of the bone and its biomechanical properties. In some cases healing is compromised, leading to delayed union or nonunion. It is estimated that 10% of the fractures which occur annually will require further surgical procedures because of impaired healing. The preferred management of nonunion and bone defects is by autologous cancellous bone grafting, because this provides the essential elements for bone formation, namely living osteogenic cells, bone-inductive proteins which stimulate cell proliferation and differentiation, and a scaffold of apatite which supports the ingrowth of newly formed bone. The supply of suitable bone, however, is limited and its harvest results in additional morbidity to the donor site, leading to pain, haematoma, or infection. For more than 30 years investigators have been developing alternative treatments, by physical or biological methods, aimed at providing the benefits of bone grafting without the complications related to harvest of an autograft. The physical strategy includes the use of mechanical stimulation, electromagnetic fields, and low-intensity ultrasound. The biological approach involves the use of osteoconductive biomaterials, growth factors which stimulate tissue repair (including bone morphogenetic proteins), and osteocompetent cells. We will review the preclinical and clinical data on each therapeutic approach and discuss potential areas of development in the field of bone healing.