Purpose: To evaluate a synthetic hydroxyapatite (HA) (manufactured in Brazil) in a rabbit model.
Methods: Nine New Zealand white rabbits underwent enucleation of one eye followed by implantation of either a 12-mm Brazilian synthetic HA implant or a 12-mm BioEye, wrapped in polyglactin 910 mesh. Magnetic resonance imaging was performed to assess fibrovascular ingrowth 4, 8, and 12 weeks after implantation. Three animals were killed at each of the times for histopathologic examination. The Brazilian implant was also examined chemically and by scanning electron microscopy.
Results: The Brazilian HA was found to be heavier than either the BioEye or synthetic FCI3 HA implants. It did not have a visible, regularly arranged interconnected porous architecture. Rather, it had randomly appearing channels apparent on its external and internal surface in addition to large cystic areas within the body of the implant. Scanning electron microscopy revealed the implant to have a microporous architecture in addition to the large channels and cystic cavities. Histopathologically, central vascularization occurred by 4 weeks and was also present at 8 and 12 weeks. In three Brazilian implants an unrecognizable, nonbirefringent material was identified. The cause of it was unclear. Chemical analysis confirmed the implant to consist of pure HA.
Conclusion: The Brazilian implant is pure HA that appears solid but has randomly arranged channels as well as a microporous architecture that allows vascularization to its center. It is heavier than other available HA implants and has the presence of an unidentified foreign material within it. Although this implant is less expensive and does not require a costly manufacturing process, the structural characteristics of the material do not offer any theoretical or clinical advantages. The implant is only available in Brazil at this time.