Growth factor expression during the development of atrophic non-union.

The aim of the study was to determine, for the first time, the distribution of expression of several important growth factors during the development of atrophic non-unions using an animal model. The sites of expression of TGFbeta, PDGF, FGFb, and BMP 2/4 were determined at the osteotomy sites of both normally healing bones and within atrophic non-unions at 1 and 8 weeks after operation using immunolocalization techniques. At 1 week after operation, the osteotomy gaps of the control group contained fracture haematoma and surrounding granulation tissue, whereas the osteotomy gaps of the non-union group contained only haematoma. The tissues of both the non-union and control groups demonstrated the same presence and distribution of growth factors. By 8 weeks after the operation, the control group osteotomy gaps were filled with bone within which the active osteoblasts stained positively for each of the growth factors. At 8 weeks, the osteotomy gaps of the non-union group contained only fibrous tissue, which failed to stain positively for any of the factors. These findings suggest that the development of atrophic non-union is not directly due to a lack of these four growth factors.