PMMA-based Bone Cement Research Articles

Modification of polymethylmethacrylate bone cement with halloysite clay nanotubes

BackgroundPolymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn’t provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics.ObjectivesThe purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers.MethodsPMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05).ResultsThe findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups.ConclusionThe novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

Implications of ageing effects on thermal and mechanical properties of PMMA-based bone cement for THA revision surgery

Loosening and infection are the main reasons for revision surgery in total hip arthroplasty (THA). Removing partially detached cemented implant components during revision surgery remains challenging and poses the risk of periprosthetic bone damage.A promising approach for a gentler removal of partially detached prostheses involves softening the PMMA-based bone cement by heating it above its glass transition temperature (TG), thus loosening the implant-cement bond. It is assumed that the TG of PMMA-based bone cement decreases in-vivo due to the gradual absorption of body fluid. Reliable data on TG are essential to develop a heat-based method for removing cemented implant components during revision surgery.The effect of water absorption was investigated in-vitro by ageing PMMA-based bone cement samples for different periods up to 56 days in both Ringer's solution (37 °C) and air (37 °C and 30% humidity). Subsequently, the TG and Vicat softening temperatures of the samples were determined by differential scanning calorimetry and Vicat tests, respectively, according to prescribed methods.Over the entire ageing period, i.e. comparing one day of ageing in air and 56 days in Ringer's solution, the Vicat softening temperature dropped by 16 °C, while the TG dropped by 10 °C for Palacos® R PMMA-based bone cement. Water absorption over time correlated significantly with the Vicat softening temperature until saturation of the PMMA-based bone cement was reached.Based on the TG and Vicat softening temperature measurements, it can be assumed that in body-aged bone cement, an optimal softening can be achieved within a temperature range of 85 °C–93 °C to loosen the bond between the PMMA-based bone cement mantle and the prosthesis stem. These findings may pave the way for a gentler removal of the implant in revision THA.

Chemical and physical properties of PMMA bone cements

PMMA-based bone cements are used for anchoring artificial joints. The cements are offered as two-component systems. During mixing, aliquid paste is formed by free-radical polymerization, which completely hardens into asolid cement matrix as polymerization progresses with an increase in viscosity. Polymerization from MMA to PMMA is an exothermic process, energy is released in the form of heat. After fixation of the prosthesis and curing of the cement, the cement fills the space between the prosthesis and the bone. With the filler PMMA, astrong force-locking and interlocking mechanical bond is created. The essential properties of PMMA cements are dictated by the powder component. In vivo, the hard and brittle bone cements absorb body fluids and become more elastic and softer. The properties of various PMMA bone cements differ significantly, although the chemical acrylate base is identical.

Bioactive and antibacterial glass particles as fillers in composite bone cements: Influence of amount and size on radio-opacity, bioactivity, mechanical and antibacterial properties

In this work, a bioactive and antibacterial glass has been added to a commercial PMMA-based bone cement to promote osteointegration and simultaneously limit bacterial contamination. The influence of the amount and size of glass powders on mechanical properties, radio-opacity, bioactivity and antibacterial effect of the composite cements has been estimated. The obtained results suggested that both filler's amount and size can affect the bending strength of the samples. The composites radio-opacity can be modulated by varying the amounts of glass and radio-opaque agent usually present in the commercial composition. The bioactive and antibacterial properties evaluation evidenced that introducing 10 wt.% of glass conferred a bioactive behaviour to the PMMA-based matrix and limited the bacterial contamination. Finally, an approach to technological transfer with controlled process parameters has been proposed.

PHSPP06 Presentation Time: 3:20 PM: A New Way to Visualize Needles for Ultrasound Prostate Brachytherapy Using Color Doppler and Needle Surface Modifications

<h3>Purpose</h3> Brachytherapy applicator conspicuity during ultrasound (US) imaging can be impaired by bowel gas, tissue interfaces, or when the applicator is far or angled with respect to the ultrasound probe. Without adequate conspicuity, applicators can be inaccurately reconstructed, leading to decreased tumor control or increased normal tissue dose due to a geometrically inaccurate treatment plan. To improve the conspicuity of titanium high-dose rate (HDR) brachytherapy needles under US imaging, the surface of needles can be modified, and color-Doppler can be utilized to highlight the surface patterns. Color-Doppler imaging can produce a twinkling signature, also referred to as a ‘twinkling artifact,' when ultrasound waves reflect from a surface with a rough or patterned structure. The twinkling signature highlights the modified applicator as variegated pixels atop a grayscale B-mode US image, enhancing conspicuity. This research was a preliminary investigation into the types of surface modifications that can produce a twinkling signature, based upon a review of prior literature that has associated surface roughness with twinkling. <h3>Materials and Methods</h3> The surfaces of 17-gauge, 25 cm titanium HDR brachytherapy needles were modified using three methods of surface modification: sandblasting with an 80-grit media, laser-etching of thin grooves, and application of a polymethyl methacrylate (PMMA)-based bone cement. Laser-etches were created on the surface of the needles using a 343 nm femtosecond laser (Pharos, Light Conversion, Lithuania) on a machining system (Photomachining Inc., USA) and were created at variable widths (0.1-1 mm) and depths (10-100 μm) without penetrating the inner lumen of the applicator. Unmodified and modified needles were imaged with a bk3000 (BK Medical, USA) with an E14CL4b transrectal probe and Logiq E9 (General Electric, USA) with a 9L linear-array transducer under B-mode and color-Doppler imaging. Needle conspicuity between needle types was assessed qualitatively in the axial and sagittal planes within a prostate phantom (CIRS, Inc., USA). <h3>Results</h3> Color-Doppler imaging in combination with surface-modified needles produced a twinkling signature with select laser-etched and PMMA-cement surface modifications. The twinkling signature appeared as a color signal atop the applicator, overlaid on grayscale B-mode ultrasound images. The twinkling signature was observed with both transrectal and linear-array ultrasound transducers. Twinkling was observed at laser-etched scribe depths >20 μm and widths >0.1 mm, and it was observed that the magnitude of the twinkling signature was dependent upon the total surface area of the etched region. It was also demonstrated that needles can be laser-etched or coated with PMMA-cement to mark a reference location with respect to the needle tip (2 cm distal). The hand-roughened needles produced a faint twinkling signature with the linear-array transducer and negligible twinkling with the transrectal transducer. Sandblasted and unmodified needles produced a negligible twinkling signature. Generally, the twinkling signature was observed to be transient in nature and dependent on the pressure between the probe and the phantom. Future work is planned to study the mechanisms underlying the color-Doppler signal and to establish an optimal surface modification and signal strength. <h3>Conclusions</h3> Color-Doppler ultrasound combined with brachytherapy applicator surface modifications may be used to enhance applicator conspicuity and aid with applicator placement and digitization. HDR brachytherapy needles may be modified for color-Doppler imaging via laser-etching or coating with a PMMA-based bone cement.

Influence of Different Nanometals Implemented in PMMA Bone Cement on Biological and Mechanical Properties.

Cemented arthroplasty is a common process to fix prostheses when a patient becomes older and his/her bone quality deteriorates. The applied cements are biocompatible, can transfer loads, and dampen vibrations, but do not provide antibacterial protection. The present work is aimed at the development of cement with antibacterial effectivity achieved with the implementation of nanoparticles of different metals. The powders of Ag, Cu with particles size in a range of 10–30 nm (Cu10) and 70–100 nm (Cu70), AgCu, and Ni were added to PMMA cement. Their influence on compression strength, wettability, and antibacterial properties of cement was assessed. The surface topography of samples was examined with biological and scanning electron microscopy. The mechanical properties were determined by compression tests. A contact angle was observed with a goniometer. The biological tests included an assessment of cytotoxicity (XTT test on human cells Saos-2 line) and bacteria viability exposure (6 months). The cements with Ag and Cu nanopowders were free of bacteria. For AgCu and Ni nanoparticles, the bacterial solution became denser over time and, after 6 months, the bacteria clustered into conglomerates, creating a biofilm. All metal powders in their native form in direct contact reduce the number of eukaryotic cells. Cell viability is the least limited by Ag and Cu particles of smaller size. All samples demonstrated hydrophobic nature in the wettability test. The mechanical strength was not significantly affected by the additions of metal powders. The nanometal particles incorporated in PMMA-based bone cement can introduce long-term resistance against bacteria, not resulting in any serious deterioration of compression strength.

A Bioglass-Based Antibiotic (Vancomycin) Releasing Bone Void Filling Putty to Treat Osteomyelitis and Aid Bone Healing.

While the infection rate after primary total joint replacements (TJR) sits at 1–2%, for trauma-related surgery, it can be as high as 3.6 to 21.2% based on the type of trauma; the risk of reinfection after revision surgery is even higher. Current treatments with antibiotic-releasing PMMA-based bone cement/ beads and/or systemic antibiotic after surgical debridement do not provide effective treatment due to fluctuating antibiotic levels at the site of infection, leading to insufficient local antibiotic concentration. In addition, non-biodegradable PMMA does not support bone regrowth in the debrided void spaces and often must be removed in an additional surgery. Here, we report a bioactive glass or bioglass (BG) substrate-based biodegradable, easy to fabricate “press fitting” antibiotic-releasing bone void filling (ABVF-BG) putty to provide effective local antibiotic release at the site of infection along with support for bone regeneration. The ABVF-BG putty formulation had homogenously distributed BG particles, a porous structure, and showed putty-like ease of handling. Furthermore, the ABVF-BG putty demonstrated in vitro antibacterial activity for up to 6 weeks. Finally, the ABVF-BG putty was biodegradable in vivo and showed 100% bacterial eradication (as shown by bacterial cell counts) in the treatment group, which received ABVF-BG putty, compared to the infection control group, where all the rats had a high bacterial load (4.63 × 106 ± 7.9 × 105 CFU/gram bone) and sustained osteomyelitis. The ABVF-BG putty also supported bone growth in the void space as indicated by a combination of histology, µCT, and X-ray imaging. The potential for simultaneous infection treatment and bone healing using the developed BG-based ABVF-BG putty is promising as an alternative treatment option for osteomyelitis.

Preparation of bioactive and antibacterial PMMA-based bone cement by modification with quaternary ammonium and alkoxysilane.

Bone cement based on poly(methyl methacrylate) (PMMA) powder and methyl methacrylate (MMA) liquid is a very popular biomaterial used for the fixation of artificial joints. However, there is a risk of this cement loosening from bone because of a lack of bone-bonding bioactivity. Apatite formation in the body environment is a prerequisite for cement bioactivity. Additionally, suppression of infection during implantation is required for bone cements to be successfully introduced into the human body. In this study, we modified PMMA cement with γ-methacryloxypropyltrimetoxysilane and calcium acetate to introduce bioactive properties and 2-(tert-butylamino)ethyl methacrylate (TBAEMA) to provide antibacterial properties. The long-term antibacterial activity is attributed to the copolymerization of TBAEMA and MMA. As the TBAEMA content increased, the setting time increased and the compressive strength decreased. After soaking in simulated body fluid, an apatite layer was detected within 7 days, irrespective of the TBAEMA content. The cement showed better antibacterial activity against Gram-negative E. Coli than Gram-positive bacteria; however, of the Gram-positive bacteria investigated, B. subtilis was more susceptible than S. aureus.

Prolonged Post-Polymerization Biocompatibility of Polymethylmethacrylate-Tri-n-Butylborane (PMMA-TBB) Bone Cement.

Polymethylmethacrylate (PMMA)-based acrylic bone cement is commonly used to fix bone and metallic implants in orthopedic procedures. The polymerization initiator tri-n-butylborane (TBB) has been reported to significantly reduce the cytotoxicity of PMMA-based bone cement compared to benzoyl peroxide (BPO). However, it is unknown whether this benefit is temporary or long-lasting, which is important to establish given that bone cement is expected to remain in situ permanently. Here, we compared the biocompatibility of PMMA-TBB and PMMA-BPO bone cements over several days. Rat femur-derived osteoblasts were seeded onto two commercially-available PMMA-BPO bone cements and experimental PMMA-TBB polymerized for one day, three days, or seven days. Significantly more cells attached to PMMA-TBB bone cement during the initial stages of culture than on both PMMA-BPO cements, regardless of the age of the materials. Proliferative activity and differentiation markers including alkaline phosphatase production, calcium deposition, and osteogenic gene expression were consistently and considerably higher in cells grown on PMMA-TBB than on PMMA-BPO, regardless of cement age. Although osteoblastic phenotypes were more favorable on older specimens for all three cement types, biocompatibility increased between three-day-old and seven-day-old PMMA-BPO specimens, and between one-day-old and three-day-old PMMA-TBB specimens. PMMA-BPO materials produced more free radicals than PMMA-TBB regardless of the age of the material. These data suggest that PMMA-TBB maintains superior biocompatibility over PMMA-BPO bone cements over prolonged periods of at least seven days post-polymerization. This superior biocompatibility can be ascribed to both low baseline cytotoxicity and a further rapid reduction in cytotoxicity, representing a new biological advantage of PMMA-TBB as a novel bone cement material.

Mechanical property, antibacterial activity and cytocompatibility of a PMMA-based bone cement loaded with clindamycin for orthopaedic surgeries

ABSTRACT Local delivery of antibiotics utilising bone cement is a well-known approach for controlling postoperative infections related to implant. 1, 5 and 10 wt.% of clindamycin (Cli) was embedded into polymethylmethacrylate (PMMA)–based bone cement for inhibiting postsurgical infection. Clindamycin antibiotic drug was homogeneously embedded into the matrix of PMMA-based cement. The results revealed that the fabricated PMMA-based cement loaded with Cli presented a high compressive strength (~120 MPa). The PMMA-based cement loaded with low Cli presented better cytocompatibility compared with its counterpart loaded with high Cli owing to the better cell attachment on the surface of the cement with a lower release of Cli. The embedding of Cli into the cement improved its antibacterial performance, as implied by the considerably improved inhibition zone with amplifying Cli concentration. Taken together, PMMA-based cement loaded with 1–5 wt% Cli might be a promising antimicrobial bone cement to be employed in orthopaedic surgeries.

Novel Osteogenic Behaviors around Hydrophilic and Radical-Free 4-META/MMA-TBB: Implications of an Osseointegrating Bone Cement.

Poly(methyl methacrylate) (PMMA)-based bone cement, which is widely used to affix orthopedic metallic implants, is considered bio-tolerant but lacks osteoconductivity and is cytotoxic. Implant loosening and toxic complications are significant and recognized problems. Here we devised two strategies to improve PMMA-based bone cement: (1) adding 4-methacryloyloxylethyl trimellitate anhydride (4-META) to MMA monomer to render it hydrophilic; and (2) using tri-n-butyl borane (TBB) as a polymerization initiator instead of benzoyl peroxide (BPO) to reduce free radical production. Rat bone marrow-derived osteoblasts were cultured on PMMA-BPO, common bone cement ingredients, and 4-META/MMA-TBB, newly formulated ingredients. After 24 h of incubation, more cells survived on 4-META/MMA-TBB than on PMMA-BPO. The mineralized area was 20-times greater on 4-META/MMA-TBB than PMMA-BPO at the later culture stage and was accompanied by upregulated osteogenic gene expression. The strength of bone-to-cement integration in rat femurs was 4- and 7-times greater for 4-META/MMA-TBB than PMMA-BPO during early- and late-stage healing, respectively. MicroCT and histomorphometric analyses revealed contact osteogenesis exclusively around 4-META/MMA-TBB, with minimal soft tissue interposition. Hydrophilicity of 4-META/MMA-TBB was sustained for 24 h, particularly under wet conditions, whereas PMMA-BPO was hydrophobic immediately after mixing and was unaffected by time or condition. Electron spin resonance (ESR) spectroscopy revealed that the free radical production for 4-META/MMA-TBB was 1/10 to 1/20 that of PMMA-BPO within 24 h, and the substantial difference persisted for at least 10 days. The compromised ability of PMMA-BPO in recruiting cells was substantially alleviated by adding free radical-scavenging amino-acid N-acetyl cysteine (NAC) into the material, whereas adding NAC did not affect the ability of 4-META/MMA-TBB. These results suggest that 4-META/MMA-TBB shows significantly reduced cytotoxicity compared to PMMA-BPO and induces osteoconductivity due to uniquely created hydrophilic and radical-free interface. Further pre-clinical and clinical validations are warranted.

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.

Antibacterial and Bioactive Composite Bone Cements

Background:: Peri-prosthetic infections are characterized by high resistance to systemic antibiotic therapy. In this work, commercial PMMA-based bone cement has been loaded with a bioactive glass doped with silver ions, with the purpose to prepare composite bone cement containing a single inorganic phase with both bioactive and antibacterial properties, able to prevent bacterial contamination. Methods:: The glass distribution in the polymeric matrix, the composites radio-opacity, the bending strength and modulus, the morphology of the fracture surfaces, the bioactivity in Simulated Body Fluid (SBF) and the antibacterial effect were evaluated. The glass particles dispersion in the polymeric matrix and their exposition on the polymer surface have been assessed by morphological and compositional characterizations via Scanning Electron Microscopy (SEM) and Energy Dispersion Spectroscopy (EDS). Results:: The introduction of the silver-doped bioactive glass allowed imparting an intrinsic radio-opacity to the cement. The bending strength and modulus were influenced by the glass preparation, amount and grain-size. The polymeric matrix did not affect the composite ability to induce hydroxyapatite precipitation on its surface (bioactivity). Moreover, antibacterial test (inhibition halo evaluation) revealed a significant antibacterial effect toward S. aureus, Bacillus, E. coli and C. albicans strains. Conclusion:: The obtained results motivate further investigations and future in vivo tests.

Modification of PMMA Cements for Cranioplasty with Bioactive Glass and Copper Doped Tricalcium Phosphate Particles.

Cranioplasty represents the surgical repair of bone defects or deformities in the cranium arising from traumatic skull bone fracture, cranial bone deformities, bone cancer, and infections. The actual gold standard in surgery procedures for cranioplasty involves the use of biocompatible materials, and repair or regeneration of large cranial defects is particularly challenging from both a functional and aesthetic point of view. PMMA-based bone cement are the most widely biomaterials adopted in the field, with at least four different surgical approaches. Modifications for improving biological and mechanical functions of PMMA-based bone cement have been suggested. To this aim, the inclusion of antibiotics to prevent infection has been shown to provide a reduction of mechanical properties in bending. Therefore, the development of novel antibacterial active agents to overcome issues related to mechanical properties and bacterial resistance to antibiotics is still encouraged. In this context, mechanical, biological, and antibacterial feature against P. aeruginosa and S. aureus bacterial strains of surgical PMMA cement modified with BG and recently developed Cu-TCP bioactive particles have been highlighted.

PMMA-Based Bone Cements and the Problem of Joint Arthroplasty Infections: Status and New Perspectives.

Polymethyl methacrylate (PMMA)-based bone cement is a biomaterial that has been used over the last 50 years to stabilize hip and knee implants or as a bone filler. Although PMMA-based bone cement is widely used and allows a fast-primary fixation to the bone, it does not guarantee a mechanically and biologically stable interface with bone, and most of all it is prone to bacteria adhesion and infection development. In the 1970s, antibiotic-loaded bone cements were introduced to reduce the infection rate in arthroplasty; however, the efficiency of antibiotic-containing bone cement is still a debated issue. For these reasons, in recent years, the scientific community has investigated new approaches to impart antibacterial properties to PMMA bone cement. The aim of this review is to summarize the current status regarding antibiotic-loaded PMMA-based bone cements, fill the gap regarding the lack of data on antibacterial bone cement, and explore the progress of antibacterial bone cement formulations, focusing attention on the new perspectives. In particular, this review highlights the innovative study of composite bone cements containing inorganic antibacterial and bioactive phases, which are a fascinating alternative that can impart both osteointegration and antibacterial properties to PMMA-based bone cement.

Graphene and graphene oxide functionalisation with silanes for advanced dispersion and reinforcement of PMMA-based bone cements.

The reinforcement of PMMA bone cements using carbon based nanomaterials has demonstrated to be a potential solution to their poor mechanical properties. The achievement of an optimal dispersion of the nanoparticles within the polymeric matrix is a crucial but not easy stage in the production of high-quality reinforced materials. In this work, a useful route for the graphene (G) functionalisation, via silanisation with (3-methacryloxypropyl) trimethoxy silane (MPS), has been developed, providing a remarkable enhancement in dispersibility and mechanical properties. With the purpose to define the critical graphene surface oxidation parameters for an optimal silanisation, different routes were thoroughly analysed using infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results showed that the silanisation significantly improved the G dispersibility: whereas the pristine G dispersion fell down within the first 24 h, the silanised G showed an adequate stability after 5 days. Additionally, this improved dispersibility produced a notable increase in the mechanical properties of the G-reinforced bone cements: in comparison with the pristine G, the compression and bending strength of silanised G increased by 12% and by 13.7% respectively and the fracture toughness by 28%. These results provide very useful information on the relevance that the characteristics of the superficial oxidation of graphene have on the effectiveness of the silanisation process, besides an interesting functionalisation procedure for advanced dispersion and reinforcement of G-PMMA bone cements.

Antibiotic elution and mechanical property of TiO2 nanotubes functionalized PMMA-based bone cements

To overcome the disadvantage of current antibiotic bone cements with low drug elution efficiency, the hollow nanostructured titanium-dioxide (TiO2) nanotubes (TNTs) were formulated with antibiotic loaded bone cement to create nano diffusion networks, enabling enhanced release of antibiotic. By incorporation of TNTs into Poly(methyl methacrylate) (PMMA) based bone cement, more than 50% of loaded antibiotic (such as gentamicin or vancomycin) could be released in two months. As comparison, only about 5% of total drug release was achieved in the absence of TNTs. The mechanical properties of PMMA-based bone cements were well preserved after incorporation of TNTs. Furthermore, the compression strength and bending modules of TNTs formulated antibiotic bone cements could be maintained after the drug release for 70 days or aging in PBS buffer for 3 months. The insoluble TNTs in bone cement is believed to support the mechanical properties after wet aging.

Effects of specimen variables and stress amplitude on the S-N analysis of two PMMA based bone cements

The fatigue performance of bone cement is influenced by the testing parameters. In previous in vitro fatigue studies, different testing conditions have been used leading to inconsistencies in the findings between the studies, and consequent uncertainties about the effects of testing specimen specifications and stress parameters. This study evaluates the role of specimen variables (namely; specimen cross-section shape, surface production method and cement composition) in a range of in vitro stress amplitudes (±12.5, ±15, ±20, ±30MPa), using S-N (Wöhler) analysis. The two main findings are: while specimen cross-section configuration and fabrication method (specimen type) played a key role in controlling the fatigue longevity of the same cement, the stress amplitude was seen as the dominant controlling variable to affect the fatigue behaviour of different cements when using the same specimen type. Thus, considering the effect of specimen type, testing at high stress amplitudes should be treated with caution, particularly in tension-compression loading, to ensure fatigue failure occurs due to mechanical rather than thermal effects and thus models the in vivo behaviour.

Preliminary focus on the mechanical and antibacterial activity of a PMMA-based bone cement loaded with gold nanoparticles

In total knee arthroplasty (TKA) and total hip replacement (THR) the restoration of the normal joint function represents a fundamental feature. A prosthetic joint must be able to provide motions and to transmit functional loads.As reported in the literature, the stress distribution may be altered in bones after the implantation of a total joint prosthesis. Some scientific works have also correlated uncemented TKA to a progressive decrease of bone density below the tibial component. Antibiotic-loaded bone cements are commonly employed in conjunction with systemic antibiotics to treat infections. Furthermore, nanoparticles with antimicrobial activity have been widely analysed. Accordingly, the current research was focused on a preliminary analysis of the mechanical and antibacterial activity of a PMMA-based bone cement loaded with gold nanoparticles. The obtained results demonstrated that nanocomposite cements with a specific concentration of gold nanoparticles improved the punching performance and antibacterial activity. However, critical aspects were found in the optimization of the nanocomposite bone cement.

Composites bone cements with different viscosities loaded with a bioactive and antibacterial glass

In this work, three commercial PMMA-based bone cements (high, medium and low viscosities) were enriched with a bioactive and Ag-containing glass to contemporaneously impart bioactive and antibacterial properties. For each formulation, the glass distribution in the polymeric matrix, the bioactivity in simulated body fluid, the silver release, the antibacterial effect and cytotoxicity were evaluated. Morphological and compositional characterizations, by means of scanning electron microscopy and energy-dispersive spectrometry, evidenced good glass dispersion in the polymeric matrix and its appreciable exposition on material surface for all composite cements. The different formulations did not entail the composite ability to induce hydroxyapatite precipitation on their surface (bioactivity) and to release silver ions. The silver release profile was comparable with the rate of infection development; moreover, antibacterial test (inhibition halo evaluation and count of colonies forming units) revealed a significant antibacterial effect towards S. aureus strain. Finally, cytotoxicity test, performed using continuous mouse fibroblast L-929, showed none cytotoxic effect of the multifunctional composite cements for all the polymeric matrix formulations.