Bone remodelling in the pores and around load bearing transchondral isoelastic porous-coated glassy carbon implants: experimental study in rabbits.

Cylinders of porous-coated glassy carbon were implanted into drill holes made through the articular surface of the medial condyle of both tibiae of ten rabbits for six and 12 weeks. Bone ingrowth and remodelling was examined by radiographic, histologic, oxytetracycline-fluorescence and microradiographic methods. Bone ingrowth into pores and load bearing implants was seen by all examination methods. Bone ingrowth occurred earlier when the pores were facing cancellous bone than cortical bone. Appositional bone formation occurred on the trabeculae a few millimetres from the interface during the early phase of remodelling at six weeks. At 12 weeks resorptive remodelling had occurred both in the surroundings and in those pores that face cancellous bone, whereas the amount of bone still increased in the pores facing cortical bone. In its porous-coated form glassy carbon functions well as a frame for ingrowing bone and it shows good osteoconductivity. Its mechanical properties are suitable for functioning as a structural bone substitute in places where the loads are mainly compressive. The difference between findings at six and 12 weeks indicated physiologic stress distribution and the adverse effects of stiff materials on bone remodelling were avoided by using this isoelastic material.