Native bovine bone morphogenetic protein improves the potential of biocoral to heal segmental canine ulnar defects

We studied the effect of a composite implant consisting of coral and native bovine bone morphogenetic protein (BMP) on the healing of 2 cm segmental d efects in the canine ulna. Plain coral and cortical autograft bone implants were used as controls. The fixation was temporary for 9 weeks with an intr amedullary Kirschner wire (6 ulnas with a composite implant of coral and BM P, 6 with plain coral and 6 with an autograft) or a plate and screws (3 uln as with a composite implant and 3 with plain coral). X-rays were taken at 3 , 6, 9, 12, 16, 26 and 36 weeks, and mechanical torsion tests were per form ed at the end of the study. The score for bone formation and bone union eva luated from radiographs was significantly higher in the composite implant g roup than in the plain coral group at 16 weeks, but the score was even high er with autografts. BMP accelerated the resorption of the coral implant. Th e mechanical strength of the composite implants was higher than that of the bones with a plain coral implant (P<0.05), while the mechanical strength o f the coral implants, even with BMP, was significantly lower than the stren gth of autografts (P<0.01). In conclusion, BMP enhanced the capacity of a c oral implant to heal a segmental ulnar defect by increasing bone formation, but the effect of this combination was not as good as that of a cortico-ca ncellous autograft.