Use of calcium phosphate cement paste in orbital volume augmentation

Background: The development of calcium phosphate in cement paste form has made its application simplified and easy. In this study, the authors used an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide/hydroxyapatite injectable calcium phosphate cement paste to evaluate its potential use in orbital volume augmentation. Methods: Five New Zealand white rabbits were used in this study. In each rabbit, the right orbit was directly implanted with calcium phosphate cement in its injectable paste form, and a prehardened form was placed in the left orbit. The orbital roof was approached through a subciliary skin incision and the implant was placed posterior to the globe of the eyeball to push it outward. Measurement of proptosis and intraocular pressure was monitored before and after implantation. The animals were killed after 3 months, and orbit bone-implant samples were taken for histology and microradiography. Results: In both groups, proptosis was induced, 4.2 +/- 0.27 mm in the prehardened group and 3.8 +/- 0.22 mm in the injectable group. These values taken 1 week postim plantation were unchanged until the end of the experiment and were maintained without significant intraocular pressure changes. The implants were well tolerated, and no sign of infection, extrusion, or migration was noted. Histologic analysis showed good biocompatibility and osteoconductivity, and micro radiography has confirmed a well-set cement with direct bone union to it. Conclusion: These findings therefore indicate that calcium phosphate cement implant, when used as an injectable paste or in its prehardened form, can be a safe, effective material for orbital volume augmentation.