Submicron-Surface Structured Tricalcium Phosphate Ceramic Enhances the Bone Regeneration in Canine Spine Environment

Calcium phosphate ceramics with submicron-scaled surface structure can trigger bone formation in non-osseous sites and are expected to enhance bone formation in spine environment. In this study, two tricalcium phosphate ceramics having either a submicron-scaled surface structure (TCP-S) or a micron-scaled one (TCP-B) were prepared and characterized regarding their physicochemical properties. Granules (size 1-2 mm) of both materials were implanted on either left or right side of spinous process, between the two lumbar vertebrae (L3-L4), and in paraspinal muscle of eight beagles. After 12 weeks of implantation, ectopic bone was observed in muscle in TCP-S explants (7.7 +/- 3.7%), confirming their ability to inductively form bone in non-osseous sites. In contrast, TCP-B implants did not lead to bone formation in muscle. Abundant bone (34.1 +/- 6.6%) was formed within TCP-S implants beside the two spinous processes, while limited bone (5.1 +/- 4.5%) was seen in TCP-B. Furthermore, the material resorption of TCP-S was more pronounced than that of TCP-B in both the muscle and spine environments. The results herein indicate that the submicron-scaled surface structured tricalcium phosphate ceramic could enhance bone regeneration as compared to the micron-scaled one in spine environment.