USE OF BONE MORPHOGENETIC PROTEIN-2 ON ECTOPIC POROUS-COATED IMPLANTSIN THE RAT

The ability of recombinant human bone morphogenetic protein 2 to remai n osteoinductive and stimulate appositional bone formation on a porous coated implant was tested in a rat quadriceps muscle pouch. Implants with or without hydroxyapatite were used to compare the effects on bon e formation of two different doses (23 mu g or 46 mu g) of recombinant human bone morphogenetic protein 2 against controls as evidenced by c ontact radiography, histologic examination, and backscatter scanning e lectron microscopic analysis, Cylindrical plasma sprayed porous titani um implants were placed bilaterally within a muscle pouch surgically c reated in 48 Lewis rats, Implants treated with recombinant human bone morphogenetic protein 2 formed significantly more bone than did contro l implants independent of the dose or presence of hydroxyapatite, In a ll implants with bone formation, osteoinduction via endochondral ossif ication began within 7 days, By 21 days, cartilage largely was replace d by bone and marrow The results of this ectopic, nonweightbearing in vivo assay suggest that recombinant human bone morphogenetic protein 2 remains biologically active after application to a titanium implant a nd may be used to enhance appositional bone formation by direct applic ation to the implant surface.