Bone morphogenetic protein 2 accelerates osteointegration and remodelling of solvent-dehydrated bone substitutes

lt was the purpose of this study to investigate how bone morphogenetic protein 2 (BMP-2) influences remodelling and the biomechanics of solvent-dehydrated bone in the long run. Furthermore, the early influence of this growth factor on the substitute was investigated.

Using a weight-bearing animal model, solvent-dehydrated bone was implanted in the tibial head of merino sheep ( n=12) after being loaded with BMP-2 (100 microg/100 microl). At 4 weeks ( n=6) and 9 months ( n=6) after surgery, histomorphological, histomorphometrical and biomechanical investigations were performed.

At 9 months after implantation of BMP-2-loaded specimens, the bone per tissue volume was high, with levels above those of physiological cancellous bone. The amount of remaining solvent-dehydrated bone was markedly decreased, and in contrast, the amount of newly formed bone was extremely high. The specimen degradation had already occurred within the first 4 weeks after implantation, showing no further impact throughout the 9-month period. Biomechanical investigations at 9 months after implantation demonstrated a yield strength which achieved levels at least equivalent to physiological cancellous bone. BMP-2 showed no significant impact on the biomechanical properties after 4 weeks, compared to specimens prior to implantation.

BMP-2 predominantly has an impact on the early implant degradation as well as bone formation, which leads to an almost completed bone remodelling of the solvent-dehydrated specimen within the study period of 9 months.