OBJECTIVETo study on the method of combining rhBMP(2) with porous-coated implants, and compared the histological and biomechanical results of 4 types of implants by being inserted into the femur of canine.

METHODS4 types of implants which are porous-coated implants (PCA), PCA implants combined with BMP, PCA implants coated with hydroxyapatite and HA coated cylindrical implants had been inserted into the femur of 16 canines. After 4, 8, 12 and 24 weeks the femur of the canines with the implants were retrieved. Bone ingrowth and shear strength of the interface was studied and analysed by the means of X-ray, soft X-ray, fluorescence tag, non-decalcification bone ground section, computer-aided image analysis procedure and biomechanical test.

RESULTSX-ray, soft X-ray, fluorescence tag, non-decalcification bone ground section and computer-aided image analysis procedure was used in histological study, and it showed that bony ingrowth into interface more than the other groups, even the maturation of newly formed bone. Non-decalcification bone ground section observation and computer aided image analysis showed the results: the new bone formation ratio of BMP group was 26.58% +/- 4.56% at 4 weeks post-implantation, which was much higher than the other groups, and there was significant difference between BMP group and each of the other group statistically (P < 0.05). Results of biomechanical study using push-out test showed that shear strength of each group appeared to rise with time. Shear strength of BMP group reached a high level at 4 weeks which was 18.94 +/- 5.11Mpa and almost twice of the other group, and there was also statistical difference between BMP group and each of the other group (P < 0.05). And the new bone formation ratio and shear strength of BMP group at 8, 12, 24 weeks post-implantation was still higher than the other group, but there was no statistically difference.

CONCLUSIONSPorous-coated implants combined with rhBMP can enhance bone ingrowth at bone-implant interface especially at the early period post-implantation. Porous-coated implants combined with rhBMP(2) can not only shorten the time of new bone formation and bone ingrowth but also enhance shear strength of bone-implant interface.