Basic fibroblast growth factor infused at different times during bone graft incorporation. Titanium chamber study in rats.

We investigated the effect of applying basic fibroblast growth factor (bFGF) to a bone graft during different stages of incorporation in an infusion bone chamber model. Bone chambers were implanted bilaterally into rat tibiae. Both chambers were connected to an implanted osmotic minipump. Ingrowing bone could enter the cylindrical interior of the chamber only at one end. The distance which ingrowing bone had reached into the bone graft was then measured on histological slides. Specimens were also analyzed by 99mTc-MDP scintimetry. The infusion of buffer during 2 weeks from implantation had no effects on tissue ingrowth distance or quality. bFGF was infused during 2 weeks from implantation in a dose of either 1.2 or 12 ng/day. Bone ingrowth was measured 6 weeks after implantation. The higher dose had a more marked effect and was used for studying the effect of application at different times. The maximum stimulation of bFGF as measured at 6 weeks postimplantation was found after infusion during the first postimplantation week. Infusion during the third and fourth weeks had no effect at 6 weeks, but tended to increase the bone ingrowth distance at 8 weeks postimplantation. These findings suggest that bFGF infusion increases bone ingrowth into bone grafts when infused at both an early and a later stage, but the effect can be measured only several weeks later.