Strength Properties of a Porous Titanium Alloy Ti6Al4V with Diamond Structure Obtained by Laser Power Bed Fusion (LPBF)

Analysis of mechanical characteristics and permeability of TPMS and Voronoi porous structure for bone scaffold

Bionic porous structure has been widely used in the field of bone implantation, because it can imitate the topological structure of bone, reduce the elastic modulus of metal bone implantation, and meet the mechanical properties and material transmission characteristics after implantation. This paper mainly studies the effects of different bionic porous structures on the mechanical and material transport properties of bone scaffolds. Firstly, under the same porosity condition, 12 groups of bionic porous structures with different shapes were designed, including G, P, D, I-type three period minimal surface (TPMS) and Voronoi porous structures with different irregularities. Then uses ABAQUS to carry out mechanical finite element simulation on different bionic porous structures, and uses Ti-6Al-4V alloy as forming material, uses laser powder bed fusion technology (LPBF) to prepare the scaffold, then carries out compression experiments. At the same time, COMSOL software is used to simulate the flow characteristics, analyze the permeability characteristics, and verified through cell experiment in vivo. The results show that the mechanical and permeability are different with vary scaffolds. In terms of topology, the morphological characteristics of TPMS are similar to trabecular bone, its compressive strength is relatively strong. Voronoi scaffold has lower elastic modulus, which can provide sufficient mechanical support while reducing stress shielding. In addition, the permeability of TPMS scaffold is better than Voronoi scaffold, which is helpful to promote cell proliferation and bone ingrowth. These bionic porous structures have their own advantages. Therefore, when designing porous structures for bone implantation, it is necessary to select the appropriate porous structure according to different bone implantation requirements. The research will help promote the clinical application of porous structures in the field of bone implantation, and provide theoretical support for the exploration of bone implantation structure design.

The Effects of Different Femoral Component Materials on Bone and Implant Response in Total Knee Arthroplasty: A Finite Element Analysis

Due to the high stiffness of the biomaterials used in total knee arthroplasty, stress shielding can lead to decreased periprosthetic bone mineral density and bone resorption. As different materials and 3D-printed highly porous surfaces are available for knee femoral components from the industry nowadays, this study aimed to compare the effects of two same-design cruciate-retaining femoral components, made with CoCr and titanium alloy, respectively, on periprosthetic bone stresses through a finite element model of the implanted knee in order to evaluate the induced stress shielding. Moreover, the effect of the cementless highly porous surface of the titanium implant was analyzed in comparison to the cemented interface of the CoCr implant. The von Mises stresses were analyzed in different periprosthetic regions of interest of the femur with different configurations and knee flexion angles. The titanium component induced higher bone stresses in comparison with the CoCr component, mostly in the medial compartment at higher knee flexion angles; therefore, the CoCr component led to more stress shielding. The model was revealed to be effective in describing the effects of different femoral component materials on bone stress, highlighting how a cementless, highly porous titanium femoral component might lead to less stress shielding in comparison to a cemented CoCr implant with significant clinical relevance and reduced bone resorption after total knee arthroplasty.

Team Approach: Metal Hypersensitivity in Total Joint Arthroplasty

»

As total joint arthroplasty volume continues to grow nationwide, more uncommon complications such as metal implant hypersensitivity are reported with greater frequency in the literature.

»

Metal hypersensitivity is a challenging diagnosis given the potentially vague symptomology. It should be considered a diagnosis of exclusion, necessitating careful consideration of other potential etiologies of a failing implant before arriving at the final diagnosis of metal hypersensitivity.

»

Patients can experience substantial morbidity from implant rejection and in severe, refractory cases may even require revision arthroplasty and conversion to a hypoallergenic implant.

»

Given the complex nature of the condition, successful treatment of metal hypersensitivity to orthopaedic implants is best achieved through the use of a multidisciplinary, team-based approach. Immunologists, radiologists, and infectious disease physicians as well as orthopaedic surgeons and mechanical engineers are all vital in appropriate diagnosis and treatment of the condition.

Parameters Influence on the Dynamic Properties of Polymer-Matrix Composites Reinforced by Fibres, Particles, and Hybrids

In this paper, we present an extensive experimental study on the dynamic mechanical properties of composites with polymer matrices, as well as a quantification of the parameters that influence these properties. Polymer-composite matrices make it possible to form any reinforcement arrangement of fibres, particles, and layers, which makes it possible to form composite materials with certain dominant mechanical properties according to the internal arrangement for the application. In this study, we focused on the dynamic properties (i.e., damping parameters, such as the loss factor (tan d), logarithmic decrement (λ), storage modulus (E′), and loss modulus (E″)) of composites with polymer matrices, including parameters such as the fibre material, fabric weaving, fibre orientation, temperature, frequency, particle size, volume of short fibres, and epoxy resin type. If other articles focus on one type of composite and 1–2 parameters, then the benefit of this article lies in our analysis of 8 mentioned parameters in the experimental analysis of 27 different types of composites with polymer matrices. The tested fibre materials were glass, aramid, and carbon; the tested woven fabrics were twill, plain, unidirectional, and satin; the temperature range was from −50 to +230 °C; the frequency was 1 Hz and 10 Hz; the particle size was 0.1–16 mm; the volume percentages of the short fibres were 3, 6, and 12 vol.% of the hybrid polymer composites and the type of polymer matrix. We used the free-damped-vibration method with vibration dynamic signal analysis and the forced-damped vibration of dynamic mechanical thermal analysis for testing. We ranked the parameters that influence the dynamic vibration properties according to the effects. Among sets of results provided in the paper, considering the storage modulus, loss modulus, and loss factor, the best results of the fibre composites were for aramid-fibre-reinforced polymers, regardless of the weave type, with an advantage for unidirectional fabric. The best results of the particle composites were for those with fine filler sizes that incorporated the short fibres.

Numerical Investigation of the Defects Effect in Additive Manufactured Ti-6Al-4V Struts on Deformation Behavior Based on Microtomographic Images

This paper describes the influence of defects occurring in struts under tension, obtained using the additive method of laser powder bed fusion (LPBF), on the stress and strain distributions. The study used struts of different thicknesses separated from Ti-6Al-4V diamond lattice structures. For numerical modeling of stress and strain fields, models that reflect the realistic shape of the tested struts with their imperfections were used. The shape of the diamond structure struts was obtained based on microtomographic measurements. Based on the results obtained, the influence of defects in the material structure on the stress and strain distribution was analyzed. It was observed that the main factor influencing the stress and strain distribution in the struts are micronotches on their external surface. These imperfections have a significantly greater impact on the stress and strain concentration than the micropores inside. Furthermore, the interactions of the imperfections are also important, which in turn affects the stress distributions and the formation of bands of high-stress values inside the material. The relationship between the presence of micropores, the stress–strain curves, and the mechanical properties of the material was also assessed.

Finite element analysis of the influence of porosity and pore geometry on mechanical properties of orthopaedic scaffolds

PURPOSE

Scaffolds play a key role in regenerative medicine in the repair of injuries, defects and cancerous changes in long bones. For this reason, scaffolds should meet certain mechanobiological requirements, such as adequate porosity and pore geometry to ensure appropriate osteointegration as well as load transfer. Taking into account the most frequently used cell units, this study attempted to evaluate the porous structures of orthopaedic scaffolds in terms of their strength parameters.

MATERIALS AND METHODS

Four pore geometries were selected for analyses: sphere, octagonal prism, cube and triangular prism, all with porosities of 10% up to 60%. Three different material properties were considered: Ti6Al4V alloy, CoCr alloy, 316 L steel. Strength compression simulations were carried out on 144 models, 72 structures of cell units with dimensions of 4 × 4 × 4 mm and 72 structures of scaffolds with a diameter of 16 mm and a height of 15 mm. Effective Young's modulus, as well as 0.2%, offset effective yield strength was estimated.

RESULTS

Research has shown that scaffolds with bone-like strength properties should be made of Ti6Al4V alloy. The value of 40% turned out to be of the best porosity. The remaining porosities showed much lower or much higher strength parameters and were significantly different from the properties of the bones.

CONCLUSIONS

The obtained data allow to indicate the most functional porous structure with Young's modulus similar to that possesses by core bone, while maintaining mechanical strength, allowing for its appropriate use in orthopaedic regenerative medicine.

Analysis of Mechanical Properties and Permeability of Trabecular-Like Porous Scaffold by Additive Manufacturing

Human bone cells live in a complex environment, and the biomimetic design of porous structures attached to implants is in high demand. Porous structures based on Voronoi tessellation with biomimetic potential are gradually used in bone repair scaffolds. In this study, the mechanical properties and permeability of trabecular-like porous scaffolds with different porosity levels and average apertures were analyzed. The mechanical properties of bone-implant scaffolds were evaluated using finite element analysis and a mechanical compression experiment, and the permeability was studied by computational fluid dynamics. Finally, the attachment of cells was observed by confocal fluorescence microscope. The results show that the performance of porous structures can be controlled by the initial design of the microstructure and tissue morphology. A good structural design can accurately match the performance of the natural bone. The study of mechanical properties and permeability of the porous structure can help address several problems, including stress shielding and bone ingrowth in existing biomimetic bone structures, and will also promotes cell adhesion, migration, and eventual new bone attachment.

Properties improvement of titanium alloys scaffolds in bone tissue engineering: a literature review

Owing to their excellent biocompatibility and corrosion-resistant properties, titanium (Ti) (and its alloy) are essential artificial substitute biomaterials for orthopedics. However, flaws, such as weak osteogenic induction ability and higher Young's modulus, have been observed during clinical application. As a result, short- and long-term postoperative follow-up has found that several complications have occurred. For decades, scientists have exerted efforts to compensate for these deficiencies. Different modification methods have been investigated, including changing alloy contents, surface structure transformation, three-dimensional (3D) structure transformation, coating, and surface functionalization technologies. The cell-surface interaction effect and imitation of the natural 3D bone structure are the two main mechanisms of these improved methods. In recent years, significant progress has been made in materials science research methods, including thorough research of titanium alloys of different compositions, precise surface pattern control technology, controllable 3D structure construction technology, improvement of coating technologies, and novel concepts of surface functionalization. These improvements facilitate the possibility for further research in the field of bone tissue engineering. Although the underlying mechanism is still not fully understood, these studies still have some implications for clinical practice. Therefore, for the direction of further research, it is beneficial to summarize these studies according to the basal method used. This literature review aimed to classify these technologies, thereby providing beginners with a preliminary understanding of the field.

Porous tantalum structure integrated on Ti6Al4V base by Laser Powder Bed Fusion for enhanced bony-ingrowth implants: In vitro and in vivo validation

Despite the widespread application of Ti6Al4V and tantalum (Ta) in orthopedics, bioinertia and high cost limit their further applicability, respectively, and tremendous efforts have been made on the Ti6Al4V-Ta alloy and Ta coating to address these drawbacks. However, the scaffolds obtained are unsatisfactory. In this study, novel high-interface-strength Ti6Al4V-based porous Ta scaffolds were successfully manufactured using Laser Powder Bed Fusion for the first time, in which porous Ta was directly manufactured on a solid Ti6Al4V substrate. Mechanical testing revealed that the novel scaffolds were biomechanically compatible, and the interfacial bonding strength was as high as 447.5 MPa. In vitro biocompatibility assay, using rat bone marrow mesenchymal stem cells (r-BMSCs), indicated that the novel scaffolds were biocompatible. Alkaline phosphatase and mineralized nodule determination demonstrated that the scaffolds favored the osteogenic differentiation of r-BMSCs. Moreover, scaffolds were implanted into rabbits with femur bone defects, and imaging and histological evaluation identified considerable new bone formation and bone ingrowth, suggesting that the scaffolds were well integrated with the host bone. Overall, these results demonstrated good mechanical compatibility, biocompatibility, and osteointegration performance of the novel Ti6Al4V-based porous Ta scaffold, which possesses great potential for orthopedic clinical applications.