Assessment of the suitability of a new brushite calcium phosphate cement for cranioplasty - an experimental study in sheep

Introduction: Aim of this experimental study was to assess the suitability of a new brushite calcium phosphate cement (chronOS(TM) Inject) for cranioplasty and to compare the results with a commercially available apatite calcium phosphate bone cement (Biobon((R))). Material and methods: A bilateral full-size craniotomy defect (23 mm in diameter) was created in the parietal bones of 18 adult Swiss Alpine sheep and filled with either chronOS(TM) Inject or BiobonO((R)). The observation intervals were 2, 4 and 6 months. Macroscopical, radiological, histological and histomorphometrical evaluations were performed. Results: New bone formation was moderate and did not differ significantly between the biomaterials. Cement resorption occurred centripetally in the chronOS(TM) Inject group and proceeded significantly faster than the degradation process of Biobod((R)). However, implantation of chronOS(TM) Inject was associated with a significantly higher rate of fibrous tissue formation. Cement resorption was mediated by macrophages in the chronOS(TM) Inject group, while osteoclasts were the predominant cell type involved in degradation of Biobon((R)). Osteoblasts were found adjacent to residual cement in both groups. Conclusion: chronOS(TM) Inject demonstrated osteoconductive properties, good biocompatibility and superior bioresorbability but none of the cements proved suitable for filling large cranial bony defects due to the high rate of fibrous tissue formation and insufficient bony regeneration. (C) 2004 European Association for Cranio Maxillofacial Surgery.