Biologic Performance of the Electrodeposited Ca-P Coatings in Rabbit Femora

Objectives: Electrolytic deposition had recently attracted more interests for its ability to coat calcium phosphate on irregular substrates at low temperatures. The aim of this study was to investigate the early bone apposition and one-year performance of the electrodeposited calcium phosphate coatings with or without chitosan in rabbit femora. Methods: Seventy-two cylindrical implants with a length of 8mm and diameter of 3.3mm were divided into three groups: electrodeposited calcium phosphate coated without chitosan, with chitosan and uncoated control. The implants were adopted special gap design and inserted into the rabbit femora. After 2, 4, 26 and 52 weeks, the implants were retrieved and analyzed for bone formation, bone-to-implant contact, and coating degradation. Results: It was found that the coatings without chitosan had the highest bone contact at early time (P<0.05). The coatings with chitosan had the least bone formation within gaps after 2, 4 and 26 weeks implantation (P<0.05). However, no difference was found among three groups after 52 weeks. Both coatings showed degradation as early as 2 weeks post-implantation. And after 52 weeks, most of the coatings had been degraded. There were no inflammatory reactions and hardly osteoclasts around the implants and the coatings. The confocal laser scanning microscopy observation further demonstrated the different bone deposition characteristics. With scanning electron microscopy, no coatings could be found on both the implants surface and bone interface. Conclusion: Our results suggest that bone apposition to both electrodeposited calcium phosphate coatings was different at early time but almost the same after 52 weeks. And both coatings showed early as well as continued degradation in the rabbit femora. The difference on bone apposition, coating degradation, and tissue reaction between two calcium phosphate coatings might be attributed to their compositional and physicochemical characteristics.