In vivo degradation and new bone formation of calcium phosphate cement-gelatin powder composite related to macroporosity after in situ gelatin degradation

Calcium phosphate cement (CPC) is reported to have excellent biocompatibility and osteoconductivity. However, its biodegradability must be improved to promote bone regeneration. We have mixed gelatin powder with CPC to create a composite containing macropores with interconnectivity. Sixty rabbits were grouped as follows: 85wt% CPC to 15wt% gelatin powder (C15), 90wt% CPC to 10wt% gelatin powder (C10), 100wt% CPC (C0) as control group and Sham group. Trabecular bone defects of distal femurs were made and implanted with the composites. The femurs were harvested for histomorphometry at 4, 12, 24 weeks after implantation, and mechanical testing at 3 days, 1, 4, 12, 24 weeks. Compared with C0, X-ray and micro-CT results of the composites revealed a progressive increase in the amount of CPCgelatin powder composite which was replaced by trabeculae. New bone area increased from 3.8 to 18% in C10, and 4.2 to 22% in C15, residual composite area decreased from 65 to 31% in C10, and 70 to 20% in C15. The compressive strength of C15 was 9.2?MPa, which was inferior to 14.6?MPa (normal cancellous bone), but was 27.4?MPa in C10 at 1 week. Further improvement of this composite may make a suitable scaffold for bone regeneration. (C) 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:11031111, 2012