Healing of segmental bone defects in rats induced by a β‐TCP‐MCPM cement combined with rhBMP‐2

A β-tricalcium phosphate-monocalcium phosphate monohydrate (β-TCP-MCPM) cement was evaluated as an effective carrier of recombinant human bone morphogenetic protein-2 (rhBMP-2) in rat femoral critical-size defects. Hard cement cylinders (4 × 5 mm) impregnated with two different doses of rhBMP-2 (1.26 or 6.28 μg) were implanted into each defect, and the results were compared with those in rats that had implantations of cylinders only. Implantation of the 6.28 μg dose of rhBMP-2 caused a large bone shell to form around the defect, resulting in osseous union in all cases within 3 weeks. Except for β-TCP granules, the cement was resorbed and replaced by bone tissue at 6 weeks. A torsion test at 9 weeks showed that the failure torque and bone stiffness had recovered 99% and 141%, respectively, compared with the intact contralateral femur. The defects that received 1.26 μg of rhBMP-2 resulted in 40% union and 41% of the failure torque at 9 weeks. However, no instances of union were observed in the defects implanted with cylinders only. In conclusion, the β-TCP-MCPM cement was shown to be effective as a rhBMP-2 carrier. Combined with rhBMP-2, this cement was rapidly resorbed and completely healed the defects. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 44, 168–175, 1999.