Abstract
Calcium magnesium phosphate cements (CMPCs) are promising bone substitutes and experience great interest in research. Therefore, in-vivo degradation behavior, osseointegration and biocompatibility of three-dimensional (3D) powder-printed CMPC scaffolds were investigated in the present study. The materials Mg225 (Ca0.75Mg2.25(PO4)2) and Mg225d (Mg225 treated with diammonium hydrogen phosphate (DAHP)) were implanted as cylindrical scaffolds (h = 5 mm, Ø = 3.8 mm) in both lateral femoral condyles in rabbits and compared with tricalcium phosphate (TCP). Treatment with DAHP results in the precipitation of struvite, thus reducing pore size and overall porosity and increasing pressure stability. Over 6 weeks, the scaffolds were evaluated clinically, radiologically, with Micro-Computed Tomography (µCT) and histological examinations. All scaffolds showed excellent biocompatibility. X-ray and in-vivo µCT examinations showed a volume decrease and increasing osseointegration over time. Structure loss and volume decrease were most evident in Mg225. Histologically, all scaffolds degraded centripetally and were completely traversed by new bone, in which the remaining scaffold material was embedded. While after 6 weeks, Mg225d and TCP were still visible as a network, only individual particles of Mg225 were present. Based on these results, Mg225 and Mg225d appear to be promising bone substitutes for various loading situations that should be investigated further.
Highlights
The use of autologous, allogenic or xenogenic grafts is still the gold standard in the surgical treatment of critical size bone defects [1,2,3]
Gelli et al [53] observed a reduction in porosity whenAMs dPeCscpraibsteeds fwoerrCeMtrePaCtepdawsteitshinDAotHhePr. in-vivo studies in a cylindrical defect model in the distal rabbit femur [27,32], the Calcium magnesium phosphate cements (CMPCs) scaffolds investigated in this study showed excellent biocompatibility without signs of inflammation, rejection or necrosis
As reported in the literature [27], the clearly visible osseous remodeling processes in the implantation area and the centripetal scaffold degradation seen in the present study indicate a partial cell-mediated dissolution of the scaffolds
Summary
The use of autologous, allogenic or xenogenic grafts is still the gold standard in the surgical treatment of critical size bone defects [1,2,3]. They cannot be used for every type of bone defect and involve various risks, such as trauma or infection at the donor site in the case of autografts [4,5], and the transmission of diseases or rejection of the implanted material in the case of allografts and xenografts [6,7]. The broader clinical application of these cements is limited by their mechanical properties, since CPCs are brittle, have only low impact strength and relatively low tensile strength [23,24]
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