[Repair of bone defects with rhBMP2 and a synthetic polymer]

Titanium is a material with good bone affinity and bone inductive properties. We used it for new type of titanium implant to facilitate bone induction through BMPs and a carrier polymer. The carrier used for rhBMP-2 was poly-lactic acid-polyethyleneglycol block copolymar (PLA-PEG). Cylindrical titanium implants were formed with a porous surface saturated with the composite BMP/PLA-PEG. A bone defect was created in the humerus of a Japanese white rabbit, and the titanium/rhBMP-2/PLA-PEG composite was implanted with the nail fixation. After eight weeks, the defect in the humerus has been completely covered over with new bone tissue. New bone formation was also found inside the titanium pores. These results suggest that the BMP/PLA-PEG composite, with which porous titanium surface had been impregnated, exuded from that surface and caused the surface of the implant to become covered with new bone. This titanium/rhBMP/PLA-PEG implant promises to be effective in treating lager bone deficits.