Bone- and non-bone-derived growth factors and effects on bone healing.

In the future, it may be possible to manipulate the fracture site with exogenous growth factors to allow successful union of the bone ends without additional surgery. The complex interaction of growth factors, the timing of their appearance and disappearance at the wound site, and the concentrations necessary to achieve specific effects must be studied more thoroughly. For growth factors to find widespread clinical use, there must be evidence that healing is enhanced. It may be difficult to enhance the healing of fresh fractures in normal animals, and it may also be difficult to demonstrate the healing of nonunion fractures. Because of the great variability in fractures of clinical patients, studies designed to determine the effect of growth factors on bone healing must be carefully designed with appropriate attention given to randomizing patients based on the risk of delayed healing and other patient characteristics.