Hydroxyapatite/β-tricalcium phosphate composite for guiding bone tissue growth into a titanium tube in 8 mm dog tibia cavity defects

We developed a fixation method and evaluate bone regrowth in the cavities of a ϕ4 mm× 8 mm titanium (Ti) tube through porous hydroxyapatite (HAP)/β-tricalcium phosphate (β-TCP) composite filling (group A), chitosan/calcium phosphate composite filling (group B), and HAP particle modification (group C). After 2 and 5 months of implantation in dog tibia defects, new bone formation in the three groups was studied by histology and histomorphometry. Group A displayed the most bone regenerated area in both 2 and 5 months post-operation. The chitosan/calcium phosphate composite in group B mostly degraded 2 months after implantation, leading to fibrous tissue invasion after 5 months. By contrast, less bone formation was observed in group C. These results indicated that filling the cavities of metal prostheses with a porous HAP/β-TCP composite can be used for stable long-term fixation in clinical settings.