Advances in materials used for minimally invasive treatment of vertebral compression fractures

Vertebral compression fractures are becoming increasingly common with aging of the population; minimally invasive materials play an essential role in treating these fractures. However, the unacceptable processing-performance relationships of materials and their poor osteoinductive performance have limited their clinical application. In this review, we describe the advances in materials used for minimally invasive treatment of vertebral compression fractures and enumerate the types of bone cement commonly used in current practice. We also discuss the limitations of the materials themselves, and summarize the approaches for improving the characteristics of bone cement. Finally, we review the types and clinical efficacy of new vertebral implants. This review may provide valuable insights into newer strategies and methods for future research; it may also improve understanding on the application of minimally invasive materials for the treatment of vertebral compression fractures.

Optimization of Mechanical and Setting Properties in Acrylic Bone Cements Added with Graphene Oxide

The extended use of acrylic bone cements (ABC) in orthopedics presents some disadvantages related to the generation of high temperatures during methyl methacrylate polymerization, thermal tissue necrosis, and low mechanical properties. Both weaknesses cause an increase in costs for the health system and a decrease in the patient’s quality of life due to the prosthesis’s loosening. Materials such as graphene oxide (GO) have a reinforcing effect on ABC’s mechanical and setting properties. This article shows for the first time the interactions present between the factors sonication time and GO percentage in the liquid phase, together with the percentage of benzoyl peroxide (BPO) in the solid phase, on the mechanical and setting properties established for cements in the ISO 5833-02 standard. Optimization of the factors using a completely randomized experimental design with a factorial structure resulted in selecting nine combinations that presented an increase in compression, flexion, and the setting time and decreased the maximum temperature reached during the polymerization. All of these characteristics are desirable for improving the clinical performance of cement. Those containing 0.3 wt.% of GO were highlighted from the selected formulations because all the possible combinations of the studied factors generate desirable properties for the ABC.

Advanced G-MPS-PMMA Bone Cements: Influence of Graphene Silanisation on Fatigue Performance, Thermal Properties and Biocompatibility

The incorporation of well-dispersed graphene (G) powder to polymethyl methacrylate (PMMA) bone cement has been demonstrated as a promising solution to improving its mechanical performance. However, two crucial aspects limit the effectiveness of G as a reinforcing agent: (1) the poor dispersion and (2) the lack of strong interfacial bonds between G and the matrix of the bone cement. This work reports a successful functionalisation route to promote the homogenous dispersion of G via silanisation using 3-methacryloxypropyltrimethoxy silane (MPS). Furthermore, the effects of the silanisation on the mechanical, thermal and biocompatibility properties of bone cements are presented. In comparison with unsilanised G, the incorporation of silanised G (G_MPS1 and G_MPS2) increased the bending strength by 17%, bending modulus by 15% and deflection at failure by 17%. The most impressive results were obtained for the mechanical properties under fatigue loading, where the incorporation of G_MPS doubled the Fatigue Performance Index (I) value of unsilanised G-bone cement-meaning a 900% increase over the I value of the cement without G. Additionally, to ensure that the silanisation did not have a negative influence on other fundamental properties of bone cement, it was demonstrated that the thermal properties and biocompatibility were not negatively impacted-allowing its potential clinical progression.

Osseointegration of Antimicrobial Acrylic Bone Cements Modified with Graphene Oxide and Chitosan

Acrylic bone cement (ABC) is one of the most used materials in orthopedic surgery, mainly for the fixation of orthopedic implants to the bone. However, ABCs usually present lack of biological activity and osseointegration capacity that leads to loosening of the prosthesis. This work reports the effect of introducing graphene oxide (GO) and chitosan (CS), separately or together, in the ABC formulation on setting performance, mechanical behavior, and biological properties. Introduction of both CS and GO to the ABC decreased the maximum temperature by 21% and increased the antibacterial activity against Escherichia coli by 87%, while introduction of only CS decreased bending strength by 32%. The results of cell viability and cell adhesion tests showed in vitro biocompatibility. The in vivo response was investigated using both subdermal and bone parietal implantations in Wistar rats. Modified ABCs showed absence of immune response, as confirmed by a normal inflammatory response in Wistar rat subdermal implantation. The results of the parietal bone implantation showed that the addition of CS and GO together allowed a near total healing bone–cement interface, as observed in the micrographic analysis. The overall results support the great potential of the modified ABCs for application in orthopedic surgery mainly in those cases where osseointegration is required.

Acrylic Bone Cements Modified with Graphene Oxide: Mechanical, Physical, and Antibacterial Properties

Bacterial infections are a common complication after total joint replacements (TJRs), the treatment of which is usually based on the application of antibiotic-loaded cements; however, owing to the increase in antibiotic-resistant microorganisms, the possibility of studying new antibacterial agents in acrylic bone cements (ABCs) is open. In this study, the antibacterial effect of formulations of ABCs loaded with graphene oxide (GO) between 0 and 0.5 wt.% was evaluated against Gram-positive bacteria: Bacillus cereus and Staphylococcus aureus, and Gram-negative ones: Salmonella enterica and Escherichia coli. It was found that the effect of GO was dependent on the concentration and type of bacteria: GO loadings ≥0.2 wt.% presented total inhibition of Gram-negative bacteria, while GO loadings ≥0.3 wt.% was necessary to achieve the same effect with Gram-positives bacteria. Additionally, the evaluation of some physical and mechanical properties showed that the presence of GO in cement formulations increased wettability by 17%, reduced maximum temperature during polymerization by 19%, increased setting time by 40%, and increased compressive and flexural mechanical properties by up to 17%, all of which are desirable behaviors in ABCs. The formulation of ABC loading with 0.3 wt.% GO showed great potential for use as a bone cement with antibacterial properties.

Enhanced Osteogenic Differentiation of Human Primary Mesenchymal Stem and Progenitor Cultures on Graphene Oxide/Poly(methyl methacrylate) Composite Scaffolds

Due to its versatility, small size, large surface area, and ability to interact with biological cells and tissues, graphene oxide (GO) is an excellent filler for various polymeric composites and is frequently used to expand their functionality. Even though the major advantage of the incorporation of GO is the enhancement of mechanical properties of the composite material, GO is also known to improve bioactivity during biomineralization and promote osteoblast adhesion. In this study, we described the fabrication of a composite bone cement made of GO and poly(methyl methacrylate) (PMMA), and we investigated its potential to enhance osteogenic differentiation of human primary mesenchymal stem and progenitor cells. Through the analysis of three differentiation markers, namely alkaline phosphatase, secreted protein acidic and rich in cysteine, and bone morphogenetic protein-2 in the presence and in the absence of an osteogenic differentiation medium, we were able to indicate a composite produced manually with a thick GO paper as the most effective among all investigated samples. This effect was related to its developed surface, possessing a significant number of voids and pores. In this way, GO/PMMA composites were shown as promising materials for the applications in bone tissue engineering.

Polymethyl Methacrylate-Based Bone Cements Containing Carbon Nanotubes and Graphene Oxide: An Overview of Physical, Mechanical, and Biological Properties

Every year, millions of people in the world get bone diseases and need orthopedic surgery as one of the most important treatments. Owing to their superior properties, such as acceptable biocompatibility and providing great primary bone fixation with the implant, polymethyl methacrylate (PMMA)-based bone cements (BCs) are among the essential materials as fixation implants in different orthopedic and trauma surgeries. On the other hand, these BCs have some disadvantages, including Lack of bone formation and bioactivity, and low mechanical properties, which can lead to bone cement (BC) failure. Hence, plenty of studies have been concentrating on eliminating BC failures by using different kinds of ceramics and polymers for reinforcement and also by producing composite materials. This review article aims to evaluate mechanical properties, self-setting characteristics, biocompatibility, and bioactivity of the PMMA-based BCs composites containing carbon nanotubes (CNTs), graphene oxide (GO), and carbon-based compounds. In the present study, we compared the effects of CNTs and GO as reinforcement agents in the PMMA-based BCs. Upcoming study on the PMMA-based BCs should concentrate on trialing combinations of these carbon-based reinforcing agents as this might improve beneficial characteristics.

Incorporation of chitosan/graphene oxide nanocomposite in to the PMMA bone cement: Physical, mechanical and biological evaluation

One of the most popular types of bone cements is polymethylmethacrylate (PMMA). The properties of this bone cement have attracted many researchers effort to modify its properties. In this study, after preparation of chitosan (Cs) powder and Cs/graphene oxide (GO) nanocomposite powder, they were added homogeneously to the PMMA bone cement with different percentages. The results showed that the addition of 25 wt% of Cs/GO nanocomposite powder to the PMMA bone cement cause to increase the compressive strength by 16.2%, the compressive modulus by 69.1% and the bending strength by 24.0%. The obtained results showed that by adding Cs/GO nanocomposite powder to the PMMA bone cement, setting time and injectability were increased, maximum temperature was decreased and apatite-like deposition was increased after 4 weeks of incubation in SBF solution. The results of MG-63 cell culture confirmed the improvement of cell viability, growth and cell adhesion for 25 wt% PMMA-Cs/GO composite bone cement. Therefore, it can be concluded that 25 wt% PMMA-Cs/GO composite bone cement with improved mechanical, physical and biological properties can be a good replacement for common commercial bone cements in orthopedic applications.

Serum-borne bioactivity caused by pulmonary multiwalled carbon nanotubes induces neuroinflammation via blood-brain barrier impairment

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) causes indirect systemic inflammation through unknown pathways. MWCNTs translocate only minimally from the lungs into the systemic circulation, suggesting that extrapulmonary toxicity may be caused indirectly by lung-derived factors entering the circulation. To assess a role for MWCNT-induced circulating factors in driving neuroinflammatory outcomes, mice were acutely exposed to MWCNTs (10 or 40 µg/mouse) via oropharyngeal aspiration. At 4 h after MWCNT exposure, broad disruption of the blood-brain barrier (BBB) was observed across the capillary bed with the small molecule fluorescein, concomitant with reactive astrocytosis. However, pronounced BBB permeation was noted, with frank albumin leakage around larger vessels (>10 µm), overlain by a dose-dependent astroglial scar-like formation and recruitment of phagocytic microglia. As affirmed by elevated inflammatory marker transcription, MWCNT-induced BBB disruption and neuroinflammation were abrogated by pretreatment with the rho kinase inhibitor fasudil. Serum from MWCNT-exposed mice induced expression of adhesion molecules in primary murine cerebrovascular endothelial cells and, in a wound-healing in vitro assay, impaired cell motility and cytokinesis. Serum thrombospondin-1 level was significantly increased after MWCNT exposure, and mice lacking the endogenous receptor CD36 were protected from the neuroinflammatory and BBB permeability effects of MWCNTs. In conclusion, acute pulmonary exposure to MWCNTs causes neuroinflammatory responses that are dependent on the disruption of BBB integrity.

Mechanical and thermal behaviour of an acrylic bone cement modified with a triblock copolymer

The basic formulation of an acrylic bone cement has been modified by the addition of a block copolymer, Nanostrength(®) (NS), in order to augment the mechanical properties and particularly the fracture toughness of the bone cement. Two grades of NS at different levels of loading, between 1 and 10 wt.%, have been used. Mechanical tests were conducted to study the behaviour of the modified cements; specific tests measured the bend, compression and fracture toughness properties. The failure mode of the fracture test specimens was analysed using scanning electron microscopy (SEM). The effect of NS addition on the thermal properties was also determined, and the polymerisation reaction using differential scanning calorimetry. It was observed that the addition of NS produced an improvement in the fracture toughness and ductility of the cement, which could have a positive contribution by reducing the premature fracture of the cement mantle. The residual monomer content was reduced when the NS was added. However this also produced an increase in the maximum temperature and the heat delivered during the polymerisation of the cement.