Review of Biomechanical Studies and Finite Element Modeling of Sternal Closure Using Bio-Active Adhesives.

The most common complication of median sternotomy surgery is sternum re-separation after sternal fixation, which leads to high rates of morbidity and mortality. The adhered sternal fixation technique comprises the wiring fixation technique and the use of bio-adhesives. Adhered sternal fixation techniques have not been extensively studied using finite element analysis, so mechanical testing studies and finite element analysis of sternal fixation will be presented in this review to find the optimum techniques for simulating sternal fixation with adhesives. The optimal wiring technique should enhance bone stability and limit sternal displacement. Bio-adhesives have been proposed to support sternal fixation, as wiring is prone to failure in cases of post-operative problems. The aim of this paper is to review and present the existing numerical and biomechanical sternal fixation studies by reviewing common sternal closure techniques, adhesives for sternal closure, biomechanical modeling of sternal fixation, and finite element modeling of sternal fixation systems. Investigating the physical behavior of 3D sternal fixation models by finite element analysis (FEA) will lower the expense of conducting clinical trials. This indicates that FEA studies of sternal fixation with adhesives are needed to analyze the efficiency of this sternal closure technique virtually.

In vitro immunomodulatory effects of novel strontium and zinc-containing GPCs.

BACKGROUND: Glass polyalkenoate cements (GPCs) are bio-adhesives which consist of ionomeric glass particles embedded in a poly-salt matrix. These materials have been used in dentistry and orthodontics extensively but are presently being optimized as bone putties for orthopedic applications. OBJECTIVE: This study utilized a patented ionomeric glass (mole fraction: SiO2:0.48, ZnO:0.36, CaO:0.12, SrO:0.04) to formulate two GPCs: GPC A (<45 µm particle size glass) and GPC B (45 µm-63 µm). These formulations were previously assessed for their effect on osteoblast viability and osteogenic function. However, the immunomodulatory effects of GPC A and B have not previously been investigated. METHOD: Non-toxic concentrations of (a) GPC dissolution products and (b) fragmented GPC particles were tested for their ability to affect the secretion of cytokines (TNF-α, IL-1ß, IL-6 and IL-10) by rat peripheral blood mononuclear cells (PBMCs), in the presence or absence of the stimulant liposaccharide (LPS). Additionally, the ionic concentrations of Sr, Zn, Ca, and Si were measured in GPC ionic extracts, and the size, shape and concentration of fragmented GPC particles in deionized water were characterized using an optical microscope-based particle analyzer. RESULTS: The results showed that GPC A ionic products reduced the concentration of TNF-α secreted by stimulated cells compared with cells stimulated in the absence of GPC products. Interestingly, the particles released from GPC A significantly increased the secretion of both TNF-α and IL-6 from unstimulated cells, compared to control cells. CONCLUSION: Neither GPC B ionic products nor released particles were found to be biologically active with respect to PBMC cytokine secretion.

Adhesion of bioactive glass-based adhesive to bone.

Understanding the failure modes and the fracture resistance is critical in evaluating the performance of an adhesive for sternal fixation. In this paper, a fracture mechanics testing methodology was used to assess the adhesion of a bioactive glass-based adhesive to bovine bone in terms of a measured mode I critical strain energy release rate (GIC). Reinforced double cantilever beam (DCB) samples were observed to produce repeatable values of GIC. The measured GIC was found to increase significantly from 5.41 to 12.60 J/m2 with an increase in adhesive thickness from 390 to 990 µm because of the constraint from the two adherends regulating the plastic zone size ahead of the crack. The specimens failed cohesively in all cases demonstrating that there was good adhesion to bone, a condition necessary to restrict micromotion and thus provide rigid sternal fixation when used along with sternal wires. It was also found that when the bone was flooded with liquid during adhesive application a much lower GIC of between 0.69 and 1.15 J/m2 was measured. Overall, the results demonstrate that the fracture mechanics approach can be used to provide a quantitative measure of the adhesion of the bioactive glass-based adhesive to the bone and that the adhesive should only be applied to clean bone in a dry environment.

Comparative Evaluation of Two Glass Polyalkenoate Cements: An In Vivo Pilot Study Using a Sheep Model.

Poly(methyl methacrylate) (PMMA) is used to manage bone loss in revision total knee arthroplasty (rTKA). However, the application of PMMA has been associated with complications such as volumetric shrinkage, necrosis, wear debris, and loosening. Glass polyalkenoate cements (GPCs) have potential bone cementation applications. Unlike PMMA, GPC does not undergo volumetric shrinkage, adheres chemically to bone, and does not undergo an exothermic setting reaction. In this study, two different compositions of GPCs (GPCA and GPCB), based on the patented glass system SiO2-CaO-SrO-P2O5-Ta2O5, were investigated. Working and setting times, pH, ion release, compressive strength, and cytotoxicity of each composition were assessed, and based on the results of these tests, three sets of samples from GPCA were implanted into the distal femur and proximal tibia of three sheep (alongside PMMA as control). Clinical CT scans and micro-CT images obtained at 0, 6, and 12 weeks revealed the varied radiological responses of sheep bone to GPCA. One GPCA sample (implanted in the sheep for 12 weeks) was characterized with no bone resorption. Furthermore, a continuous bone-cement interface was observed in the CT images of this sample. The other implanted GPCA showed a thin radiolucent border at six weeks, indicating some bone resorption occurred. The third sample showed extensive bone resorption at both six and 12 weeks. Possible speculative factors that might be involved in the varied response can be: excessive Zn2+ ion release, low pH, mixing variability, and difficulty in inserting the samples into different parts of the sheep bone.

In vivo analysis of a proprietary glass-based adhesive for sternal fixation and stabilization using rabbit and sheep models.

Wire cerclage remains the standard method of care for sternal fixation, following median sternotomy, despite being beset with complications. An emerging treatment option has been to augment the wires with an adhesive. A patented ionomeric glass (mole fraction: SiO2:0.48, ZnO:0.36, CaO:0.12, SrO:0.04) has been used to formulate GPC+, a glass polyalkenoate cement (GPC), by mixing it with poly(acrylic) acid (PAA) and de-ionized water. In a human cadaver study, this material, when applied with wire cerclage, was able to significantly reduce sternal instability. However, the material has yet to be tested in pertinent animal models. Here, after a series of physical and mechanical tests to confirm suitability of the experimental material for implantation, three samples of GPC+ were implanted in either the tibia or femur of three different rabbits, alongside sham defects, for two different time modalities. A further seven samples of GPC+ and one poly(methyl methacrylate) control (PMMA) were implanted in either the tibia or femur of two different sheep. The sheep containing the PMMA was sacrificed at 8 weeks and the other at 16 weeks, to evaluate time dependent biological response. Upon sacrifice, microCT images were acquired and histology slides prepared for analysis. All three GPC+ samples implanted in the rabbit model, for the two time modalities, were characterized by minimal bone resorption along with a mild inflammatory response. Five of the seven GPC+ materials implanted in the sheep model (all three implanted for 8 weeks and two of those implanted for 16 weeks) were associated with mild to moderate immune response, comparable to that observed with PMMA, as well as mild bone resorption. The remaining two GPC + materials (implanted in the sheep model for 16 weeks) exhibited no bone resorption or inflammatory response and appeared to stimulate increased bone density at the implant site. These results suggest that GPC + can be a viable bone adhesive for use in hard tissue applications such as sternal fixation and stabilization. Experiments performed to synthesize & test Sr-doped glass adhesive for sternal fixation. (1) Sr-doped ionomeric glass fired, ground down and mixed with aqueous polyacrylic acid to produce the adhesive. (2) Adhesive characterized and tested by a suite of laboratory-based tests to ensure suitability for implantation. (3) Adhesive implanted into a rabbit model (distal femur, 12 weeks post implantation) where micro-CT images confirmed an excellent bone/cement interface, no evidence of bone resorption and some bone remodelling. (4) Adhesive subsequently implanted into a sheep model; at 16-weeks, a continuous bone-adhesive interface is seen suggesting no bone resorption. There was an increase in the peri-implant radiodensity, suggesting enhanced mineral content of the bone surrounding the GPC+ implant.

In vitro evaluation of novel titania-containing borate bioactive glass scaffolds.

Titanium-containing borate bioactive glass scaffolds (0, 5, 15, and 20 mol %, identified as BRT0, BRT1, BRT3, and BRT4) with a microstructure similar to that of human trabecular bone were prepared and evaluated in vitro for potential bone loss applications in revision total knee arthroplasty (rTKA). Methyl thiazolyl tetrazolium (MTT) cell viability assays of scaffold ion release extracts revealed that BRT0 scaffolds (0 mol % titanium) inhibited cell proliferation and activity at day 14. At day 30, all scaffold extracts decreased cell proliferation and activity significantly. However, live/dead cell assay results demonstrated that degradation products from all the scaffolds had no inhibitory effect on cell viability. Significant bactericidal efficacies of BRT3 extracts against Escherishia coli (Gram-negative) and BRT1 extracts against Staphylococcus aureus and Staphylococcus epidermidis (both Gram-positive bacteria) were demonstrated. Finally, evaluation of the cell/bioactive glass surface interactions showed well-spread cells on the surface of the BRT3 glass discs and BRT1 and BRT3 scaffolds, when compared to BRT0 and BRT4 scaffolds. The results indicate that by changing the Ti4+ :B3+ ratio, the ion release and consequently cell proliferation could be improved. in vitro results in this study demonstrate that BRT3 scaffolds could be a promising candidate for addressing bone loss in rTKAs; however, in vivo studies would be required to evaluate the effect of a dynamic environment on the cell and tissue response to the fabricated scaffolds.

In vitro osteogenic performance of two novel strontium and zinc-containing glass polyalkenoate cements.

Glass polyalkenoate cements (GPCs) are under investigation as potential bone adhesives, as they may provide an alternative to polymethylmethacrylate-based cements. GPCs containing strontium (Sr) and zinc (Zn) in place of aluminium (Al) are of particular interest because these ions are known stimulators of osteoprogenitor differentiation. GPCs have been manufactured from a novel bioactive glass (SiO2 :0.48, ZnO:0.36, CaO:0.12, SrO:0.04) in the past, but, while such materials have been assessed for their influence on viability, their influence on osteogenic function has not been investigated until now. For this study, two GPCs were formulated from the same glass precursor evaluated in previous studies. These GPCs were named GPC A and GPC B, and they differed in glass particle size, polyacrylic acid molecular weight, and their powder: liquid ratios. The effect of these two GPCs on osteogenic differentiation of primary rat osteoblasts were evaluated using three culture systems: culture with dissolution extracts, indirect contact with transwell-inserts and direct contact. Additionally, the degradation characteristics of GPCs were assessed, including their interfacial pH and surrounding pH. The experimental outcomes revealed that collagen deposition, alkaline phosphatase expression, and mineralization were largely dependent on GPC composition as well as the mode of interaction with cells. These markers were found to be significantly elevated in response to GPC A's dissolution products. However, osteogenic differentiation was inhibited when osteoblasts were cultured indirectly and directly with GPCs, with, overall, GPC B significantly outperforming GPC A. These results suggest that GPC degradation products effect osteogenic differentiation in a dose-dependent manner.

Lab on a rod: Size-based particle separation and sorting in a helical channel.

Size-based particle separation using inertial microfluidics in spiral channels has been well studied over the past decade. Though these devices can effectively separate particles, they require a relatively large device footprint with a typical outer channel radius of approximately 15 mm. In this paper, we describe a microfluidic device with a footprint diameter of 5.5 mm, containing a helical channel capable of inertial particle separation fabricated using abrasive jet micromachining. The separation of particles in several channel geometries was studied using wide-field fluorescence microscopy. A maximum separation efficiency of approximately 90% was achieved at a flow rate of 1.5 ml/min with a purity of approximately 95% at the outlet, where large particles were collected. An accompanying computational fluid dynamics model was developed to allow researchers to quickly assess the separation capability of their helical or spiral devices.

A novel abrasive water jet machining technique for rapid fabrication of three-dimensional microfluidic components.

Microfluidic lab-on-a-chip devices are usually fabricated using replica molding, with poly(dimethylsiloxane) (PDMS) casting on a mold. Most common techniques used to fabricate microfluidic molds, such as photolithography and soft lithography, require costly facilities such as a cleanroom, and complicated steps, especially for the fabrication of three-dimensional (3D) features. For example, an often-desired 3D microchannel feature consists of intersecting channels with depth variations. This type of 3D flow focusing geometry has applications in flow cytometry and droplet generation. Various manufacturing techniques have recently been developed for the rapid fabrication of such 3D microfluidic features. In this paper, we describe a new method of mold fabrication that utilizes water jet cutting technology to fabricate free-standing structures on mild steel sheets to make a mold for PDMS casting. As a proof-of-concept, we use this fabrication technique to make a PDMS chip that has a 3D flow focusing junction, an inlet for the sample fluid, two inlets for the sheath fluid, and an outlet. The flow focusing junction is patterned into the PDMS slab with an abrupt, nearly stepwise change to the depth of the microchannel junction. We use confocal microscopy to visualize the 3D flow focusing of a sample flow using this geometry, and we also use the same geometry to generate water-in-oil droplets. This alternative approach to create microfluidic molds is versatile and may find utility in reducing the cost and complexity involved in fabricating 3D features in microfluidic devices.

Calcium sulfate-containing glass polyalkenoate cement for revision total knee arthroplasty fixation.

Poly(methyl methacrylate) (PMMA) bone cement is used as a minor void filler in revision total knee arthroplasty (rTKA). The application of PMMA is indicated only for peripheral bone defects with less than 5 mm depth and that cover less than 50% of the bone surface. Treating bone defects with PMMA results in complications as a result of volumetric shrinkage, bone necrosis, and aseptic loosening. These concerns have driven the development of alternative bone cements. We report here on novel modified glass polyalkenoate cements (mGPCs) containing 1, 5 and 15 wt% calcium sulfate (CaSO4 ) and how the modified cements' properties compare to those of PMMA used in rTKA. CaSO4 is incorporated into the mGPC to improve both osteoconductivity and bioresorbability. The results confirm that the incorporation of CaSO4 into mGPCs decreases the setting time and increases release of therapeutic ions such as Ca2+ and Zn2+ over 30 days of maturation in deionized (DI) water. Moreover, the compressive strength for 5 and 15 wt% CaSO4 addition increased to over 30 MPa after 30 day maturation. Although the overall initial compressive strength of the mGPC (~ 30 MPa) is less than PMMA (~ 95 MPa), the compressive strength of mGPC is closer to that of cancellous bone (~ 1.2-7.8 MPa). CaSO4 addition did not affect biaxial flexural strength. Fourier transform infrared analysis indicated no cross-linking between CaSO4 and the GPC after 30 days. in vivo tests are required to determine the effects the modified GPCs as alternative on PMMA in rTKA.

A review of the latest insights into the mechanism of action of strontium in bone.

Interest in strontium (Sr) has persisted over the last three decades due to its unique mechanism of action: it simultaneously promotes osteoblast function and inhibits osteoclast function. While this mechanism of action is strongly supported by in vitro studies and small animal trials, recent large-scale clinical trials have demonstrated that orally administered strontium ranelate (SrRan) may have no anabolic effect on bone formation in humans. Yet, there is a strong correlation between Sr accumulation in bone and reduced fracture risk in post-menopausal women, suggesting Sr acts via a purely physiochemical mechanism to enhance bone strength. Conversely, the local administration of Sr with the use of modified biomaterials has been shown to enhance bone growth, osseointegration and bone healing at the bone-implant interface, to a greater degree than Sr-free materials. This review summarizes current knowledge of the main cellular and physiochemical mechanisms that underly Sr's effect in bone, which center around Sr's similarity to calcium (Ca). We will also summarize the main controversies in Sr research which cast doubt on the 'dual-acting mechanism'. Lastly, we will explore the effects of Sr-modified bone-implant materials both in vitro and in vivo, examining whether Sr may act via an alternate mechanism when administered locally.

The Role of Poly(Methyl Methacrylate) in Management of Bone Loss and Infection in Revision Total Knee Arthroplasty: A Review.

Poly(methyl methacrylate) (PMMA) is widely used in joint arthroplasty to secure an implant to the host bone. Complications including fracture, bone loss and infection might cause failure of total knee arthroplasty (TKA), resulting in the need for revision total knee arthroplasty (rTKA). The goals of this paper are: (1) to identify the most common complications, outside of sepsis, arising from the application of PMMA following rTKA, (2) to discuss the current applications and drawbacks of employing PMMA in managing bone loss, (3) to review the role of PMMA in addressing bone infection following complications in rTKA. Papers published between 1970 to 2018 have been considered through searching in Springer, Google Scholar, IEEE Xplore, Engineering village, PubMed and weblinks. This review considers the use of PMMA as both a bone void filler and as a spacer material in two-stage revision. To manage bone loss, PMMA is widely used to fill peripheral bone defects whose depth is less than 5 mm and covers less than 50% of the bone surface. Treatment of bone infections with PMMA is mainly for two-stage rTKA where antibiotic-loaded PMMA is inserted as a spacer. This review also shows that using antibiotic-loaded PMMA might cause complications such as toxicity to surrounding tissue, incomplete antibiotic agent release from the PMMA, roughness and bacterial colonization on the surface of PMMA. Although PMMA is the only commercial bone cement used in rTKA, there are concerns associated with using PMMA following rTKA. More research and clinical studies are needed to address these complications.

Effect of TiO2 doping on degradation rate, microstructure and strength of borate bioactive glass scaffolds.

A titanium-containing borate glass series based on the system (52-X) B2O3-12CaO-6P2O5-14Na2O-16ZnO-XTiO2 with X varying from 0, 5 and 15 mol% of TiO2 incorporated, identified as BRT0, BRT1 and BRT3, respectively, were used in this study. Scaffolds (pore sizes, 165-230 µm and porosity, 53.51-69.51%) were prepared using a polymer foam replication technique. BRT3 scaffolds exhibited higher compressive strength (7.16 ±â€¯0.22 MPa) when compared to BRT0 (6.02 ±â€¯0.47 MPa) and BRT1 (5.65 ±â€¯0.28 MPa) scaffolds with lower, or no, TiO2 content. The solubility of the scaffolds decreased as the TiO2 content increased up to 15 mol% when samples of each scaffold were immersed in DI water and the pH of all these extracts went up from 7.0 to 8.5 in 30 days. The cumulative ion release from the scaffolds showed significant difference with respect to TiO2 content; addition of 5 mol% TiO2 at the expense of borate (B2O3) decreased the ion release remarkably. Furthermore, it was found that for all three scaffolds, cumulative ion release increased with incubation time. The results indicate that the degradation rates and compressive strengths of borate bioactive glass scaffolds could be controlled by varying the amount of TiO2 incorporated, confirming their potential as scaffolds in TKA and rTKA.

A review of materials for managing bone loss in revision total knee arthroplasty.

In 2014-2015, 61,421 total knee arthroplasties (TKAs) were performed in Canada; an increase of about 20% over 2000-2001. Revision total knee arthroplasties (rTKAs) accounted for 6.8% of TKAs performed between 2014 and 2015, and this is estimated to grow another 12% by 2025. rTKAs are typically more complicated than primary TKAs due to the significant loss of femoral and tibial bone stock. The escalating demand and limitations associated with total knee arthroplasty and their revision drives the development of novel treatments. A variety of materials have been utilized to facilitate regeneration of healthy bone around the site of a knee arthroplasty. The selection of these materials is based on the bone defect size and includes bone grafts, graft substitutes and cements. However, all these materials have certain disadvantages such as blood loss, disease transmission (bone grafts), inflammatory response, insufficient mechanical properties (bone graft substitutes) thermal necrosis and stress shielding (bone cement). Recently, the use of metal augments for large bone defects has attracted attention, however they can undergo fretting, corrosion, and stress shielding. All things considered, this review indicates the necessity of developing augments that have structural integrities and biodegradation rates similar to that of human bone. Therefore, the future of bone loss management may lie in fabricating novel bioactive glass augments as they can promote bone healing and implant stability and can degrade with time.

Measurement of Adhesion of Sternal Wires to a Novel Bioactive Glass-Based Adhesive.

Stainless steel wires are the standard method for sternal closure because of their strength and rigidity, the simplicity of the process, and the short healing time that results from their application. Despite this, problems still exist with sternal stability due to micromotion between the two halves of the dissected and wired sternum. Recently, a novel glass-based adhesive was developed which, in cadaveric trials and in conjunction with wiring, was shown to restrict this micromotion. However, in order to avoid complications during resternotomy, the adhesive should adhere only to the bone and not the sternal wire. In this study, sternal wires were embedded in 8 mm discs manufactured from the novel glass-based adhesive and the constructs were then incubated at 37 °C for one, seven, and 30 days. The discs were manufactured in two different thicknesses: 2 and 3 mm. Wire pull-out tests were then performed on the constructs at three different strain rates (1, 0.1, and 0.01 mm/min). No statistically significant difference in pull-out force was found regardless of incubation time, loading rate, or construct thickness. The pull-out forces recorded were consistent with static friction between the wire and adhesive, rather than the adhesion between them. Scanning electron micrographs provided further proof of this. These results indicate that the novel adhesive may be suitable for sternal fixation without complicating a potential resternotomy.

Novel adhesives for sternal fixation and stabilization: A biomechanical analysis.

BACKGROUND: Cerclage wires remain the current standard of care following median sternotomy, despite significant complications including dehiscence and infection. This study uses a human cadaveric model to investigate the use of glass polyalkenoate cements formulated from two glasses, A (mole fraction: SiO2:0.48, ZnO:0.36, CaO:0.12, SrO:0.04) and B (mole fraction: SiO2:0.48, ZnO:0.355, CaO:0.06, SrO:0.08, P2O5:0.02, Ta2O5:0.005), to improve wired sternal fixation. METHODS: Median sternotomies were performed on fifteen cadaveric sterna. Fixation was performed with either traditional wire cerclage or adhesive-enhanced wire cerclage; the adhesive based on either Glass A or Glass B. Cyclic tensile loading of 10 N to 100 N was applied. Every 30 cycles, the maximum load was increased by 100 N up to a maximum of 500 N. Two adhered sterna were tested beyond 500 N. Mid-sternal displacement was measured to assess fixation stability. FINDINGS: Displacement for adhesive-enhanced sternal closures were significantly less (p < 0.05) than standard wire cerclage. There was no significant difference between adhesives. Up to 500 N, no adhesive-enhanced sternum experienced a pathological sternal displacement (>2 mm), while three out of five of traditional wire fixations did. Of the two adhered samples tested beyond 500 N, one showed pathological displacement at 800 N and the other at 1100 N. Failure of adhered sterna appeared to initiate within the trabecular bone rather than in the adhesive. INTERPRETATION: The adhesives were capable of providing immediate bone stability, significantly reducing sternal displacement. In vivo investigations are warranted to determine the effect the adhesives have on bone remodelling.

Novel adhesives for distal radius fixation: A biomechanical analysis.

Wrist fractures can be difficult to treat due to advanced age of the patient, medical co-morbidities, and comminution of the bone. This study examines the effectiveness of two injectable glass polyalkenoate cements (GPCs), derived from two different glasses (A and B), as minimally invasive treatments for distal radius fractures. Twenty-seven fresh cadaveric radial pairs were tested either in compressive fatigue or to quasi-static compressive failure. The radii tested to failure had one pair fixated with a GPC while the other was left intact. The radii tested under fatigue had one pair fixated with a GPC and the other with a volar locking plate. A wedge osteotomy was used to simulate a severely comminuted fracture. When loaded to failure, the radii fixated with a GPC made from glass A or B were found to be, respectively, at least 57% and 62% as strong as their intact biological pair (95% Confidence Interval, Lower). Using a paired t-test, the radii fixated with either adhesive were found to be significantly stiffer than their biological pairs fixated with a volar locking plate for all cycles of fatigue loading. The adhesives under investigation demonstrate promise as treatment for distal radius fractures. In vivo investigations are warranted to determine the effect that the adhesives have on the bone remodelling process.

Percutaneous upper extremity fracture fixation using a novel glass-based adhesive.

OBJECTIVE: To develop a surgical technique for percutaneous upper extremity fracture fixation using a novel glass-based adhesive. METHODS: Three intact upper extremity cadaveric specimens with undisturbed soft tissues were obtained. Two were used to model a wrist fracture, and the third to model a proximal humerus fracture. Fractures were produced using a small osteotome in a percutaneous fashion. Banna Bone Adhesive (BBA) was delivered to the fracture site percutaneously using a 16 gauge needle under bi-planar fluoroscopic guidance. After setting of the adhesive, the specimens were dissected to qualitatively assess BBA delivery and placement. RESULTS: The adhesive could readily be delivered through the 16 gauge needle with an appropriate amount of pressure applied to the syringe. Using the fluoroscope, the adhesive could be seen to flow into the fracture site with minimal extravagation into the surrounding soft tissues. Successful bonding of the fracture fragments was observed. CONCLUSIONS: Percutaneous delivery of BBA into a fracture of the distal radius and proximal humerus may be a feasible fracture fixation technique. Biomechanical testing and animal model testing are required to further develop this procedure.

Titanium addition influences antibacterial activity of bioactive glass coatings on metallic implants.

In an attempt to combat the possibility of bacterial infection and insufficient bone growth around metallic, surgical implants, bioactive glasses may be employed as coatings. In this work, silica-based and borate-based glass series were synthesized for this purpose and subsequently characterized in terms of antibacterial behavior, solubility and cytotoxicity. Borate-based glasses were found to exhibit significantly superior antibacterial properties and increased solubility compared to their silica-based counterparts, with BRT0 and BRT3 (borate-based glasses with 0 and 15 mol% of titanium dioxide incorporated, respectively) outperforming the remainder of the glasses, both borate and silicate based, in these respects. Atomic Absorption Spectroscopy confirmed the release of zinc ions (Zn2+), which has been linked to the antibacterial abilities of glasses SRT0, BRT0 and BRT3, with inhibition effectively achieved at concentrations lower than 0.7 ppm. In vitro cytotoxicity studies using MC3T3-E1 osteoblasts confirmed that cell proliferation was affected by all glasses in this study, with decreased proliferation attributed to a faster release of sodium ions over calcium ions in both glass series, factor known to slow cell proliferation in vitro.

Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion.

Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate's (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex.