Biocompatibility and osseointegration of β-TCP: Histomorphological and biomechanical studies in a weight-bearing sheep model

The aim of the study was to investigate the biocompatibility, degradation, and biomechanical properties of beta-TCP (Cerasorb) in a weight-bearing sheep model. beta-TCP implant prototypes were implanted in the tibial head of adult merino sheep. After 6 and 12 months material explants were harvested for biomechanical, histological, and histomorphometrical analysis. Corresponding bone specimens of the intact bone of the contralateral leg were used as controls in the biomechanical test. Compression tests showed higher values for maximum fracture load, yield strength, and compression modulus after 6 and 12 months compared to control. Microscopically, the implants showed good osteoconduction and were incorporated into the bone; however, relevant amounts of beta-TCP were still present after 12 months. Histomorphological results revealed that beta-TCP had partially degraded between implantation and 6 months, but its share remained constant between 6 and 12 months. The bone volume fraction in the area of the implant (46% +/- 6.5%) was initially higher than in the corresponding bone area of the contralateral leg (31% +/- 9.6%), but after 12 months declined to 29% +/- 9.4% (control: 33% +/- 8.3%), while the share of beta-TCP remained constant at 36% +/- 12.2%. These findings were supported by microradiographic data. In conclusion, in a weight bearing implantation model beta-TCP showed good biocompatibility, osseointegration and beginning degradation, even though it was not further degraded between 6 and 12 months.