gms | German Medical Science

Objective: Bone morphogentic proteins (BMPs) belong to the group of transforming growth factor (TGF-β) proteins and were shown to have numerous biological effects of which the osteoinductive ability is the most outstanding. By means of surface modification it has recently become possible to immobilize rhBMP-2 on implant sufaces. As only few publications deal with rhBMP-2 effects in otology the present study aims to evaluate both BMP effects and BMP-“coating” of titanium implants in the woven petrous bone.

Material and Methods: A total of 36 titanium cylindrical dumb-bell shaped implants were manufactured containing equivalent composites as used for ossicular replacement prothesis. Subsequent to creating ultrahydrophilic, bioadhesiv surfaces, one third of the implants was used for immobilization of rhBMP-2. In 18 rabbits one titanium sample each was implanted in both tympanic bullae comparing the groups of immobilized rhBMP-2 vs. rhBMP-2-free, soluble rhBMP-2 vs. rhBMP-2-free and immobilized vs. soluble rhBMP-2. The formation of new bone in this gap healing model was observed by microradiographic and histomorphometric analysis.

Results: A significant amount of new bone contacting the surface of the implants was detected in the gap given by the shape of the implants. Bone formation was enhanced both in the immobilized and soluble rhBMP-2-group compared to the control groups.

Conclusion: It was shown for the first time that rhBMP-2 induces new bone formation in the woven petrous bone. Due to the immobilization this effect is restricted to the implant surface. Thus preventing ectopic bone formation. rhBMP-2-coating of titanium surfaces might improve the osseointegration of otologic implants.