Osseointegration of hydroxyapatite and remodeling‐resorption of tricalciumphosphate ceramics

Abstract

Cancellous bone defects surrounded by still intact bone structures never heal. Ceramics offer a solution providing osteoconductive scaffolds. The purpose of the study is to evaluate whether structured β-TCP and HA implants can reconstruct cancellous bone defects, which role micro- and macro-porosity, stiffness and surface area play; finally the indication for both materials based on its resorbability. 10 German Shepard dogs were operated on both tibial heads implanting shell-like fully interconnected ceramic cylinders, using a wet grinding hollow drill coated with diamonds. β-TCP was compared with HA. A polychromatic sequential labelling with 4 different fluorochromes controlled bone formation dynamics. Non-decalcifying histology after perfusion fixation and vessel casting was performed. μ-CT was combined with high resolution microradiography and histology on thin ground crossections. The stages after 6 weeks, 2, 3, 4 months and 15 months were evaluated. In spite of osseointegration of HA and β-TCP, the osseointegration of both materials was completely different. Both shell-like bone void fillers were osseointegrated in a sandwich-like manner. HA yielded primarily a reinforcement of the recipient's cancellous-bone bed and full osseointegration after 4 months, whereas β-TCP-implants were fully osseointegrated after 6 weeks. HA did not show signs of resorption. The resorption of the β-TCP resulted during remodelling. The final stage showed restitution "ad integrum" of the β-TCP defects with a physiological architecture, whereas HA was integrated in the cancellous bone construction providing 600 μm measuring macropores showing osteoinductive properties.