Tissue response to implants of calcium phosphate ceramic in the rabbit spine

Recent studies have shown that porous calcium phosphates provide a scaffold for bony ingrowth in various anatomic sites. In this preliminary investigation a type of porous calcium phosphate ceramic was implanted in the vertebral columns of 21 rabbits; the ceramic was studied as a possible bone graft substitute for use in spinal fusions. Animals were killed at three, six, eight, 12, and 24 weeks. Roentgenograms and histologic sections of the implant site were then obtained. Bony tissue ingrowth was progressing during the study period. Woven bone was found by six weeks after implantation, and lamellar bone was evident at 12 weeks. By 12 weeks the bony ingrowth had reached the central portion of the ceramic block. There was no fibrous tissue barrier to normal ossification. This type of calcium phosphate ceramic is compatible with bony ingrowth when implanted in the vertebral column of rabbits.