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A novel application of calcium phosphate-based bone cement as an adjunct procedure in adult craniofacial reconstruction.

ABSTRACT: Secondary corrective osteotomy of malunited craniofacial fractures can be a challenging proposition. The exposure, extrusion, and palpability of the titanium implants used become a genuine concern especially in areas of relatively thin skin, such as the periorbital region. Restoring a satisfactory contour to the midface is another major task for the plastic surgeon. Bone cement used to reconstruct craniofacial defects has existed for many years. However, most applications have been as a substitute for autogenous bone grafts for defects less than 25 cm(2). In this article, we present two cases of malunited facial fractures that underwent corrective osteotomy, during which we felt that despite the conventional osteotomy and reduction techniques, there was still either a small remnant step deformity or suboptimal contour smoothness due to prominence of the implants used. We thus used bone cement as a resurfacing medium over titanium implants to restore good malar contour and reduce the palpability and exposure rate of the titanium implants. We report good patient satisfaction with contour correction with no increase in wound infection rates or any delay in wound healing. There was initial chemosis associated with the use of the bone cement, which resolved in both patients within 3 to 4 weeks. Postoperative computed tomography showed some degree of osteointegration but no fraction of the bone cement. Calcium phosphate bone cement thus presents an attractive adjunctive method for midfacial contour resurfacing, when used in conjunction with conventional osteotomy procedures and as an onlay over prominent titanium implants.

SUBMITTER: Ho S

PROVIDER: S-EPMC3314250 | biostudies-other | 2011 Dec

REPOSITORIES: biostudies-other

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Project description:Calcium phosphate cements (CPCs) have been extensively investigated as scaffolds in bone tissue engineering in light of their chemical composition closely resembling the mineral component of bone extracellular matrix. Yet, the degradation kinetics of many CPCs is slow compared to de novo bone formation. In order to overcome this shortcoming, the use of porogens within CPCs has been suggested as a potential strategy to increase scaffold porosity and promote surface degradation. This study explored the usage of glucose microparticles (GMPs) as porogens for the introduction of macroporosity within CPCs, and characterized the handling properties and physicochemical characteristics of CPCs containing GMPs. Samples were fabricated with four different weight fractions of GMPs (10, 20, 30, and 40%) and two different size ranges (100-150μm and 150-300μm), and were assayed for porosity, pore size distribution, morphology, and compressive mechanical properties. Samples were further tested for their handling properties - specifically, setting time and cohesiveness. Additionally, these same analyses were conducted on samples exposed to a physiological solution in order to estimate the dissolution kinetics of GMPs and its effect on the properties of the composite. GMPs were efficiently encapsulated and homogeneously dispersed in the resulting composite. Although setting times increased for GMP/CPC formulations compared to control CPC material, increasing the Na2HPO4 concentration in the liquid phase decreased the initial setting time to clinically acceptable values (i.e. <15min). Incorporation of GMPs led to the formation of instant macroporosity upon cement setting, and encapsulated GMPs completely dissolved in three days, resulting in a further increase in scaffold porosity. However, the dissolution of GMPs decreased scaffold compressive strength. Overall, the introduction of GMPs into CPC resulted in macroporous scaffolds with good handling properties, as well as designer porosity and pore size distribution via selection of the appropriate size/weight fraction of GMPs. The data demonstrate that GMPs are promising porogens for the production of highly tunable porous CPC scaffolds.Statement of significanceCalcium phosphate cements have shown great promise for the regeneration of bone. However, macropores (>100μm) are required for promoting bone ingrowth. Several studies have investigated methods to generate macroporosity within calcium phosphate cements but many of these methods either affect the cement setting or take weeks or months to generate the maximum porosity. This work offers a new method for generating macroporosity within calcium phosphate cements by utilizing glucose microparticles. The microparticles dissolve in less then 72h, thereby generating scaffolds with maximum porosity in short period of time. The results will offer a new method for generating macroporosity within calcium phosphate cements.

Project description:A blue calcium phosphate cement with optimal self-hardening properties was synthesized by doping whitlockite (?-TCP) with copper ions. The mechanism and the kinetics of the cement solidification process were studied using energy dispersive X-ray diffraction and it was found out that hardening was accompanied by the phase transition from TCP to brushite. Reduced lattice parameters in all crystallographic directions resulting from the rather low (1:180) substitution rate of copper for calcium was consistent with the higher ionic radius of the latter. The lower cationic hydration resulting from the partial Ca?Cu substitution facilitated the release of constitutive hydroxyls and lowered the energy of formation of TCP from the apatite precursor at elevated temperatures. Addition of copper thus effectively inhibited the formation of apatite as the secondary phase. The copper-doped cement exhibited an antibacterial effect, though exclusively against Gram-negative bacteria, including E. coli, P. aeruginosa and S. enteritidis. This antibacterial effect was due to copper ions, as demonstrated by an almost negligible antibacterial effect of the pure, copper-free cement. Also, the antibacterial activity of the copper-containing cement was significantly higher than that of its precursor powder. Since there was no significant difference between the kinetics of the release of copper from the precursor TCP powder and from the final, brushite phase of the hardened cement, this has suggested that the antibacterial effect was not solely due to copper ions, but due to the synergy between cationic copper and a particular phase and aggregation state of calcium phosphate. Though inhibitory to bacteria, the copper-doped cement increased the viability of human glial E297 cells, murine osteoblastic K7M2 cells and especially human primary lung fibroblasts. That this effect was also due to copper ions was evidenced by the null effect on viability increase exhibited by the copper-free cements. The difference in the mechanism of protection of dehydratases in prokaryotes and eukaryotes was used as a rationale for explaining the hereby evidenced selectivity in biological response. It presents the basis for the consideration of copper as a dually effective ion when synergized with calcium phosphates: toxic for bacteria and beneficial for the healthy cells.

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A novel application of calcium phosphate-based bone cement as an adjunct procedure in adult craniofacial reconstruction.

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