Evaluation of Elution and Mechanical Properties of High-Dose Antibiotic-Loaded Bone Cement: Comparative "In Vitro" Study of the Influence of Vancomycin and Cefazolin.

Use of antibiotic-loaded bone cements is one of the most effective methods for the prevention and treatment of prosthetic joint infection. However, there is still controversy about the optimal combination and doses of antibiotics that provide the maximum antimicrobial effect without compromising cement properties. In this study, vancomycin and cefazolin were added to a bone cement (Palacos R+G). Antibiotic release, fluid absorption, and mechanical properties were evaluated under physiological conditions. The results show that the type of antibiotic selected has an important impact on cement properties. In this study, groups with cefazolin showed much higher elution than those containing the same concentration of vancomycin. In contrast, groups with cefazolin showed a lower strength than vancomycin groups.

Characterization of the conversion of bone cement and borate bioactive glass composites.

Borate bioactive glass 13-93B3 converts into an osteoconductive hydroxyapatite-like material in a liquid medium. In this study, 13-93B3 was incorporated into a commercial PMMA (poly(methyl methacrylate)) bone cement, and the conversion of the glass into a precipitate in solution was investigated with scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared (spectroscopy)-attenuated total reflection, and micro-Raman spectroscopy. Glass particles of 5, 33, and 100 µm diameter were each mixed with the PMMA cement to create 20, 30, and 40% glass-loaded composites. Precipitate formation was found to be a calcium-deficient apatite partially substituted with magnesium ions that resembles native bone material and would ideally encourage bone growth better than stoichiometric hydroxyapatite. Composites of bone cement and 13-93B3 show promise as a means of encouraging bone attachment to the surface of the bone cement.

Mechanical and degradation properties of poly(methyl methacrylate) cement/borate bioactive glass composites.

Bone cement is used extensively in orthopedics to anchor prostheses to bone and fill voids. Incorporating bioactive glass into poly(methyl methacrylate) (PMMA)-based bone cement could potentially improve its effectiveness for these tasks. This study characterizes the mechanical and degradation properties of composites containing PMMA-based bone cement and particles of borate bioactive glass designated as 13-93B3. Glass particles of size 5, 33, and 100 µm were mixed with PMMA bone cement to create composites containing 20, 30, and 40 wt % glass. Composites and a bone cement control were soaked in phosphate-buffered saline. Compressive strength, Young's modulus, weight loss, water uptake, solution pH, and ionic concentrations were measured over 21 days. The compressive strengths of composites decreased over 21 days. Average Young's moduli of the composites remained below 3 GPa. Weight loss and water uptake of specimens did not exceed 2 and 6%, respectively. Boron concentrations and pH of all solutions increased over time, with higher glass weight fractions leading to higher pH values. Results demonstrated that the composite can sustain glass degradation and ionic release without compromising short-term mechanical strength.

Enhancing mechanical properties of an injectable two-solution acrylic bone cement using a difunctional crosslinker.

Two-solution bone cements modified with ethylene glycol-dimethacrylate (EG-DMA) as a crosslinker have been developed as an attempt to further improve the mechanical properties of acrylic bone cement. The result of this study shows that EG-DMA can increase the mechanical properties and fractional monomer conversion while preserving the thermal characteristics. The strength and bending modulus increase with EG-DMA concentrations at 5-10 vol % EG-DMA. Substituting the EG-DMA content past 10 vol % decreases the bending properties due to the effects of reduced monomer concentrations. Strengthened EG-DMA samples demonstrated an increase in ductility with noticeably different fracture surface morphologies than the control samples, indicated by microtroughs and ridge formation caused by excessive plastic strain. This work provides insight into the effect of substituting a crosslinker for MMA monomer in an injectable two-solution system and lays out the ideal concentrations of EG-DMA for superior mechanical or fractional monomer conversion properties. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 783-790, 2019.

Comparison of in vitro biocompatibility of silicone and polymethyl methacrylate during the curing phase of polymerization.

Adverse events have been reported with acrylic bone cements. However, current test standards for acrylic materials fail to characterize the potentially harmful monomers released during the curing stage. In clinical applications, materials are implanted into the human body during this phase. Silicone may be a safer alternative to acrylic cements. Silicone is used in medical applications for its biocompatibility and stability characteristics. Previously, no study has been completed which compares silicone to acrylic cements. In this study, both materials were injected into the cell medium during the curing process which more accurately reflects clinical use of material. Initially, cell cultures followed ASTM standard F813-07 which fails to capture the effects of monomer released during curing. Subsequently, a modified cell culture method was employed which evaluated cytotoxicity while the materials cured. The objective of this study was to capture toxicity data during curing phase. Thus, the test method employed measured and excluded the impact of the exothermic reaction temperature of polymethyl methacrylate (PMMA) on cell growth. The concentration of PMMA monomer was measured at 1 and 24 h after injecting PMMA into culture plates in a manner consistent with established cell growth methodologies. Our results indicate current in vitro cytotoxicity assays recommended by ASTM standards are unable to reveal the real cytotoxic effect caused by methyl methacrylate monomers during polymerization. Our modified experiment can more accurately illustrate the true nature of the toxicity of materials and improve assay results. In these tests, silicone based elastomeric polymers showed excellent cytocompatibility. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2693-2699, 2018.