Bone Elastic Modulus Research Articles

Bone mechanical properties were altered in a mouse model of multiple myeloma bone disease

Multiple myeloma bone disease (MMBD) is characterized by the growth of malignant plasma cells in bone marrow, leading to an imbalance in bone (re)modeling favoring excessive resorption. Loss of bone mass and altered microstructure characterize MMBD in humans and preclinical animal models, although, no study to date has examined bone composition or material properties. We hypothesized that MMBD alters bone composition, mineral crystal properties and mechanical properties in the MOPC315.BM.Luc model after intra-tibial injection of myeloma cells and three weeks of daily in vivo tibial loading. Decreased cortical bone elastic modulus and hardness measured by nanoindentation of tibiae were observed in MM-injected mice compared to PBS-injected mice, whereas cortical bone composition, mineral crystal properties measured by Fourier-transform infrared imaging or small angle X-ray scattering, respectively remained unchanged. However, MM-injected mice had thinner cancellous bone mineral particles compared to PBS-injected mice. Mechanical loading did not lead to altered cortical bone composition, mineral structure, or mechanical properties in the context of MM. Unexpectedly, we observed the intra-tibial injection itself altered the material composition of bone, manifested by increased matrix mineralization and crystal size of the hydroxyapatite crystals in the bone matrix. In conclusion, our data suggest that mechanical stimuli can be used as an adjuvant bone anabolic therapy in patients with MMBD to rebuild bone with unaltered composition and mineral structure to reduce subsequent fracture risk.

Probabilistic Finite Element Analysis of Human Rib Biomechanics: A Framework for Improved Generalizability.

In dynamic impact events, thoracic injuries often involve rib fractures, which are closely related to injury severity. Previous studies have investigated the behavior of isolated ribs under impact loading conditions, but often neglected the variability in anatomical shape and tissue material properties. In this study, we used probabilistic finite element analysis and statistical shape modeling to investigate the effect of population-wide variability in rib cortical bone tissue mechanical properties and rib shape on the biomechanical response of the rib to impact loading. Using the probabilistic finite element analysis results, a response surface model was generated to rapidly investigate the biomechanical response of an isolated rib under dynamic anterior-posterior load given the variability in rib morphometry and tissue material properties. The response surface was used to generate pre-fracture force-displacement computational corridors for the overall population and a population sub-group of older mid-sized males. When compared to the experimental data, the computational mean response had a RMSE of 4.28N (peak force 94N) and 6.11N (peak force 116N) for the overall population and sub-group respectively, whereas the normalized area metric when comparing the experimental and computational corridors ranged from 3.32% to 22.65% for the population and 10.90% to 32.81% for the sub-group. Furthermore, probabilistic sensitivities were computed in which the contribution of uncertainty and variability of the parameters of interest was quantified. The study found that rib cortical bone elastic modulus, rib morphometry and cortical thickness are the random variables that produce the largest variability in the predicted force-displacement response. The proposed framework offers a novel approach for accounting biological variability in a representative population and has the potential to improve the generalizability of findings in biomechanical studies.

Research on 3D printed titanium alloy scaffold structure induced osteogenesis: Mechanics and in vitro testing

Several methods exist for repairing mandibular segmental bone defects, typically employing the implant method to accomplish the repair. Following a comparative analysis, the Ti6Al4V structural scaffold implant was chosen for bone defect repair. Triply periodic minimal surface (TPMS) is characterized by a high surface area to volume ratio, an average curvature of zero, and other notable advantages, providing a new line of thinking for bone tissue scaffolds. In this work, the in vitro osteogenesis of a cell unit measuring 4 mm was investigated. First, the finite element analysis (FEA) method and the mechanical experiment method were employed to screen the elasticity modulus of the cancellous bone of the mandible. Subsequently, the selective laser melting (SLM) technique was adopted to prepare three different structures precisely - Gyroid, octahedron, and cube - each with wall thicknesses of 0.3 mm, 0.4 mm, and 0.5 mm. In the in vitro osteogenic experiments, it was observed through confocal laser scanning microscopy (CLSM) that each scaffold displayed favorable cell spreading at 1 day and 3 days. Moreover, osteoblast cell adhesion and proliferation assays revealed improved cell adhesion and proliferation with prolonged co-cultivation time, signifying the excellent biocompatibility of the structural titanium alloy scaffolds. Furthermore, findings from cell differentiation and bioactivity assays indicated that the Gyroid structure exhibited superior osteogenesis compared to the cube and octahedron structures. However, no statistically significant difference was noted between varying wall thicknesses within the same structure.

Fabrication, microstructure and properties of 10Ti-5 Nb-1Sn biomedical β titanium alloy with low elastic modulus and high strength-ductility synergy

The new generation of β-type titanium alloy with low elastic modulus and high strength-ductility synergy has a good future in biomedical materials. In this paper, a 10Ti-5 Nb-1Sn alloy was designed by D-electron theory and fabricated by vacuum arc melting. Then the effect of cold-rolling and heat treatment on the evolution of microstructure, tensile properties and elastic modulus of 10Ti-5 Nb-1Sn alloy was systematically studied. The results have shown that the as-casted 10Ti-5 Nb-1Sn ingot consists of single β phase, the tensile strength is 473 MPa, the elongation is 35% and the elastic modulus is 36 GPa. The cold-rolling could obviously enhance the tensile strength to 823 MPa due to the high-density dislocation tangles and reduce the Young's modulus to 32 GPa due to the formation of {001}<110> texture, but the elongation significantly decreased. After annealing, the 10Ti-5 Nb-1Sn alloys could obtain a high strength-ductility synergy, i.e., tensile strength is 713 MPa and elongation is 23%, and low elastic modulus (33 GPa), which is close to human bone elastic modulus (10–30 GPa) and has the potential to be used as metallic biomedical materials.

Regional variation of the cortical and trabecular bone material properties in the rabbit skull.

The material properties of some bones are known to vary with anatomical location, orientation and position within the bone (e.g., cortical and trabecular bone). Details of the heterogeneity and anisotropy of bone is an important consideration for biomechanical studies that apply techniques such as finite element analysis, as the outcomes will be influenced by the choice of material properties used. Datasets detailing the regional variation of material properties in the bones of the skull are sparse, leaving many finite element analyses of skulls no choice but to employ homogeneous, isotropic material properties, often using data from a different species to the one under investigation. Due to the growing significance of investigating the cranial biomechanics of the rabbit in basic science and clinical research, this study used nanoindentation to measure the elastic modulus of cortical and trabecular bone throughout the skull. The elastic moduli of cortical bone measured in the mediolateral and ventrodorsal direction were found to decrease posteriorly through the skull, while it was evenly distributed when measured in the anteroposterior direction. Furthermore, statistical tests showed that the variation of elastic moduli between separate regions (anterior, middle and posterior) of the skull were significantly different in cortical bone, but was not in trabecular bone. Elastic moduli measured in different orthotropic planes were also significantly different, with the moduli measured in the mediolateral direction consistently lower than that measured in either the anteroposterior or ventrodorsal direction. These findings demonstrate the significance of regional and directional variation in cortical bone elastic modulus, and therefore material properties in finite element models of the skull, particularly those of the rabbit, should consider the heterogeneous and orthotropic properties of skull bone when possible.

Bone density optimized pedicle screw insertion.

Background: Spinal fusion is the most common surgical treatment for the management of degenerative spinal disease. However, complications such as screw loosening lead to painful pseudoarthrosis, and are a common reason for revision. Optimization of screw trajectories to increase implant resistance to mechanical loading is essential. A recent optimization method has shown potential for determining optimal screw position and size based on areas of high bone elastic modulus (E-modulus). Aim: The aim of this biomechanical study was to verify the optimization algorithm for pedicle screw placement in a cadaveric study and to quantify the effect of optimization. The pull-out strength of pedicle screws with an optimized trajectory was compared to that of a traditional trajectory. Methods: Twenty-five lumbar vertebrae were instrumented with pedicle screws (on one side, the pedicle screws were inserted in the traditional way, on the other side, the screws were inserted using an optimized trajectory). Results: An improvement in pull-out strength and pull-out strain energy of the optimized screw trajectory compared to the traditional screw trajectory was only observed for E-modulus values greater than 3500MPacm3. For values of 3500MPacm3 or less, optimization showed no clear benefit. The median screw length of the optimized pedicle screws was significantly smaller than the median screw length of the traditionally inserted pedicle screws, p < 0.001. Discussion: Optimization of the pedicle screw trajectory is feasible, but seems to apply only to vertebrae with very high E-modulus values. This is likely because screw trajectory optimization resulted in a reduction in screw length and therefore a reduction in the implant-bone interface. Future efforts to predict the optimal pedicle screw trajectory should include screw length as a critical component of potential stability.

Effects of blood flow restriction training on bone turnover markers, microstructure, and biomechanics in rats.

The present study aimed to investigate the effects of blood flow restriction training on muscle strength, bone tissue structure material, and biomechanical properties in rats applying various exercise interventions and to analyze the process by identifying the bone turnover markers, it provides a theoretical basis for the application of BFRT in clinical rehabilitation. A total of 24, 3-month-old male SD (Sprague Dawley) rats were randomly divided into pressurized control group (CON, n=6), low-intensity training group (LIRT, n=6), high-intensity training group (HIRT, n=6), and blood flow restriction training group (LIBFR, n=6) for 8-week ladder-climbing exercises. The pressured control group were given only ischemia treatments and did not undertake any burden. The low-intensity training group was allowed to climb the ladder with 30% of the maximum voluntary carrying capacity (MVCC). The rats in the high-intensity training group were allowed to climb the ladder with 70% MVCC. The blood flow restriction training group climbed the ladder with 30% MVCC while imposing blood flow restriction. Before sampling, the final MVCC was measured using a ladder-climbing protocol with progressively increasing weight loading. The serum, muscle, and bone were removed for sampling. The concentrations of the bone turnover markers PINP, BGP, and CTX in the serum were measured using ELISA. The bone mineral density and microstructure of femur bones were measured using micro-CT. Three-point bending and torsion tests were performed by a universal testing machine to measure the material mechanics and structural mechanics indexes of the femur bone. The results of maximum strength test showed that the MVCC in LIRT, HIRT, and LIBFR groups was significantly greater than in the CON group, while the MVCC in the HIRT group was significantly higher than that in the LIRT group (P<0.05). According to the results of the bone turnover marker test, the concentrations of bone formation indexes PINP (amino-terminal extension peptide of type I procollagen) and BGP (bone gla protein) were significantly lower in the CON group than in the HIRT group (P<0.01), while those were significantly higher in the LIRT group compared to the HIRT group (P<0.01). In terms of bone resorption indexes, significant differences were identified only between the HIRT and other groups (P<0.05). The micro-CT examination revealed that the HIRT group had significantly greater bone density index values than the CON and LIRT groups (P<0.05). The results of three-point bending and torsion test by the universal material testing machine showed that the elastic modulus and maximum load indexes of the HIRT group were significantly smaller than those of the LIBFR group (P<0.05). The fracture load indexes in the HIRT group were significantly smaller than in the LIBFR group (P<0.05). 1. LIRT, HIRT, LIBFR, and CON all have significant differences, and this training helps to improve maximum strength, with HIRT being the most effective. 2. Blood flow restriction training can improve the expression of bone turnover markers, such as PINP and BGP, which promote bone tissue formation. 3. Blood flow restriction training can improve muscle strength and increase the positive development of bone turnover markers, thereby improving bone biomechanical properties such as bone elastic modulus and maximum load.

HAp-Ti-6Al-4V Interface Fretting Wear Failure Prediction in Different Bio-lubricants using FEM

Plasma-sprayed hydroxyapatite (HAp) coated titanium alloy (Ti-6Al-4V) has been widely used as the material for artificial hip implants. However, studies have greatly challenged their long-time usage due to fretting wear behavior at the HAp-Ti-6Al-4V interface. Wear particles from the HAp coating may activate inflammation at surrounding organs, further leading to implant loosening, implant failures and even total hip replacement (THR) revision surgeries. Hence, present research aims to adopt the finite element methodology (FEM) in predicting fretting wear failure at the HAp-Ti-6Al-4V interface of uncemented hip implant femoral stem component under different body environments (bio-lubricants). A finite element (FE) model based on the half-cylinder on flat contact configuration subjected to actual mechanical and tribological properties under different bio-lubricants is developed with the modified Archard wear equation adopted to examine the fretting wear behavior through simulations. A parametric study is then conducted to evaluate the combined effects of different mechanical and tribological properties, including HAp coating thickness, bone elastic modulus and loading condition, under different bio-lubricants on the fretting wear behavior of HAp-Ti-6Al-4V interface. Lastly, single and multiple regression analyses are performed to formulate fretting wear predictive equation that acts as a fast-fretting wear failure prediction tool. The FE predicted results in this paper prove that the maximum wear depth at HAp-Ti-6Al-4V interface is promoted under lower coefficient of friction (COF), smaller HAp coating thickness, smaller bone elastic modulus and larger intensity of fatigue loading. The formulated predictive equations suggest a strong correlation between independent and dependent variables due to R-squared (R2) values being larger than 0.75 which guarantee goodness of fit.

Stress concentration in bone tissues and screw dental implants

Analysis of stress concentration in bone tissues and screw dental implants was per-formed on a model of screw join of the implant and surrounding bone tissues under the action of normal and tangential loads. The computations were performed by the bounda-ry element method for the plane strain state. It was assumed that those hollows in the spongy bone, which had formed in the bone after the implant insertion, are conformed to the screw thread on the implant. Bone tissues are considered as an isotropic and homo-geneous linear-elastic materials. It has been found that with the increasing in the spongy bone tissue elastic modulus, the maximum equivalent stresses in this bone tissue in-crease. Stresses in the cortical bone tissue decrease with the increasing in the spongy bone elastic modulus due to the decreasing in the load transferred to this bone part. Stresses in the spongy bone decrease with the increasing of the cortical bone layer elas-ticity modulus. The level of maximum stress in the cortical layer of the bone increases with the increasing of this bone tissue elastic modulus. The maximum of stresses in the cortical bone tissue are observed near the implant neck.

Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness

PurposeSince the biomedical implants with an improved compressive strength, near bone elastic modulus, controlled porosity, and sufficient surface roughness, can assist in long term implantation. Therefore, the fine process tuning plays its crucial role to develop optimal settings to achieve these desired properties. This paper aims to find applications for fine process tuning in laser powder bed fusion of biomedical Ti alloys for load-bearing implants.Design/methodology/approachIn this work, the parametric porosity simulations were initially performed to simulate the process-induced porosity for selective laser-melted Ti6Al4V as per full factorial design. Continually, the experiments were performed to validate the simulation results and perform multiresponse optimization to fine-tune the processing parameters. Three levels of each control variable, namely, laser power – Pl (180, 190, 200) W, scanning speed – Vs (1500, 1600, 1700) mm/s and scan orientation – ϴ{1(0,0), 2(0,67°), 3(0,90°)} were used to investigate the processing performance. The measured properties from this study include compressive yield strength, elastic modulus, process-induced porosity and surface roughness. Finally, confirmatory experiments and comparisons with the already published works were also performed to validate the research results.FindingsThe results of porosity parametric simulation and experiments in selective laser melting of Ti6Al4V were found close to each other with overall porosity (less than 10%). The fine process tuning was resulted in optimal settings [Pl (200 W), Vs (1500 mm/s), ϴ (0,90°)], [Pl (200 W), Vs (1500 mm/s), ϴ (0,67°)], [Pl (200 W), Vs (1500 mm/s), ϴ (0,0)] and [Pl (200 W), Vs (1500 mm/s), ϴ (0,0)] with higher compressive strength (672.78 MPa), near cortical bone elastic modulus (12.932 GPa), process-induced porosity (0.751%) and minimum surface roughness (2.72 µm). The morphology of the selective laser melted (SLMed) surface indicated that the lack of fusion pores was prominent because of low laser energy density among the laser and powder bed. Confirmatory experimentation revealed that an overall percent improvement of around 15% was found between predicted and the experimental values.Originality/valueSince no significant works are available on the collaborative optimization and fine process tuning in laser powder bed fusion of biomedical Ti alloys for different load bearing implants. Therefore, this work involves the comprehensive investigation and multi-objective optimization to determine optimal parametric settings for better mechanical and physical properties. Another novel aspect is the parametric porosity simulation using Ansys Additive to assist in process parameters and their levels selection. As a result, selective laser melted Ti alloys at optimal settings may help in examining the possibility for manufacturing metallic implants for load-bearing applications.

Potential assessment in laser powder bed fusion of bionic porous Ti scaffolds concerning compressive behavior, porosity, and surface roughness

The fabrication of cellular structures with biocompatible materials for implants has increased in recent years because of human aging and traffic road accidents. Laser powder bed fusion or Selective laser melting (SLM) can fabricate various load-bearing implants with mass customization in design and manufacturing. This work involves a manufacturability study in selective laser melting of biomedical Ti alloy implant plug for Osteoarthritis patients. The investigation involved the control variables like laser power (175,185,195) watt, scanning speed (1100,1250,1400) mm/s, and hatch spacing (0.065,0.0725,0.08) mm alongwith output responses such as Compressive yield strength, Elastic modulus, porosity, and surface roughness. The experiments were performed using Box Behnken design in Response surface modelling for collaborative optimization. The results were explicitly explained with an in-depth process physics supported with Characterization involving Scanning electron microscopy, Electro-dispersive spectroscopy, X-ray diffraction, micro-computed tomography, optical profilometry analyses, and process schematics. The optimal setting with laser power (195 W), scanning speed (1100 mm/s), and hatch spacing (0.068 mm) yielded high compressive yield strength (22.41 MPa), near trabecular bone Elastic modulus (0.891GPa), controlled porosity formation (29.32 %), and optimal surface roughness (3.647 μm). Topography resulted in a prominent lack of fusion pores because of low energy density levels, whereas the optimal settings produced around 15 % improvement from design of experiments data.

FINITE ELEMENT ANALYSIS OF THE IMPINGING HIP: SUBJECT-SPECIFIC MODELS TO ASSESS THE RISK OF OSTEOARTHRITIC DEGENERATION

Femoro-acetabular impingement involves a deformity of the hip joint and is associated with hip osteoarthritis. Although 15% of the asymptomatic population exhibits a deformity, it is not clear who will develop symptoms. Current diagnostic imaging measures have either low specificity or low sensitivity and do not consider the dynamic nature of impingement during daily activities. The goal of this study is to determine stresses in the cartilage, subchondral bone and labrum of normal and impinging hips during activities such as walking and sitting down.Quantitative CT scans were obtained of a healthy Control and a participant with a symptomatic femoral cam deformity (‘Bump’). 3D models of the hip were created from automatic segmentation of CT scans. Cartilage layers were added so the articular surface was the mid-line of the joint. Finite element meshes were generated in each region. Bone elastic modulus was assigned element-by-element, calculated from CT intensity converted to bone mineral density using a calibration phantom. Cartilage was modelled as poroelastic, E=0.467 MPa, v=0.167, and permeability 3×10-16 m4/N s. The pelvis was fixed while rotations and contact forces from Bergmann et al. (2001) were applied to the femur over one load cycle for walking and sitting in a chair. All analyses were performed in FEBio.High shear stresses were seen near the acetabular cartilage-labrum junction in the Bump model, up to 0.12 MPa for walking and were much higher than in the Control.Patient-specific modelling can be used to assess contact and tissue stresses during different activities to better understand the risk of degeneration in individuals, especially for activities that involve high hip flexion. The high stresses at the cartilage labrum interface could explain so-called bucket-handle tears of the labrum.

Effect of radiation-induced damage of trabecular bone tissue evaluated using indentation and digital volume correlation

Exposure to X-ray radiation for an extended amount of time can cause damage to the bone tissue and therefore affect its mechanical properties. Specifically, high-resolution X-ray Computed Tomography (XCT), in both synchrotron and lab-based systems, has been employed extensively for evaluating bone micro-to-nano architecture. However, to date, it is still unclear how long exposures to X-ray radiation affect the mechanical properties of trabecular bone, particularly in relation to lab-XCT systems. Indentation has been widely used to identify local mechanical properties such as hardness and elastic modulus of bone and other biological tissues. The purpose of this study is therefore, to use indentation and XCT-based investigative tools such as digital volume correlation (DVC) to assess the microdamage induced by long exposure of trabecular bone tissue to X-ray radiation and how this affects its local mechanical properties. Trabecular bone specimens were indented before and after X-ray exposures of 33 and 66 h, where variation of elastic modulus was evaluated at every stage. The resulting elastic modulus was decreased, and micro-cracks appeared in the specimens after the first long X-ray exposure and crack formation increased after the second exposure. High strain concentration around the damaged tissue exceeding 1% was also observed from DVC analysis. The outcomes of this study show the importance of designing appropriate XCT-based experiments in lab systems to avoid degradation of the bone tissue mechanical properties due to radiation and these results will help to inform future studies that require long X-ray exposure for in situ experiments or generation of reliable subject-specific computational models.

Assessing Mg/Si3N4 biodegradable nanocomposites for osteosynthesis implants with a focus on microstructural, mechanical, in vitro corrosion and bioactivity aspects

Magnesium-based biodegradable implant materials for the osteosynthesis process (fixation or stabilizing of a fractured bone) are on the verge of being used clinically. However, the rapid degradation of magnesium-based materials in the physiological environment results in a loss of mechanical integrity before the complete healing of the fracture site. To address this issue, the present study used Silicon Nitride (Si3N4) nanoparticles to improve the in-vitro degradation resistance along with the mechanical strength and ductility of Magnesium. The Si3N4 nanoparticles were homogeneously reinforced in the pure Magnesium matrix through the ultrasonic-assisted stir casting method. Moreover, the effect of Si3N4 nanoparticles on microstructure, mechanical, in-vitro corrosion and bioactivity response of Mg/Si3N4 nanocomposites was studied. Notably, the inclusion of 1.0 vol% Si3N4 nanoparticles increased tensile strength by 1.4 times and ductility by two times. In addition, the elastic modulus of Mg/Si3N4 nanocomposites is within the range of local cortical bone elastic modulus. In-vitro immersion experiments in simulated physiological fluids revealed a 2.2-fold reduction in degradation rate compared to pure Magnesium. Moreover, the addition of Si3N4 nanoparticles enhanced the in-vitro bioactivity, as the surface of the nanocomposites showed a high needle-like Ca–P apatite layer with a 1.41 Ca/P ratio of the deposited layer close to hydroxyapatite's Ca/P ratio (1.64). Overall, this study provides the basis for the fabrication of stable yet completely biodegradable Mg/Si3N4 nanocomposite bone implants for the osteosynthesis process.

Formulating delamination-fretting wear failure predictive equation in HAp coated hip arthroplasty using multiple linear regression model

Present paper addresses the formulation of delamination-fretting wear failure predictive equation in HAp-Ti-6Al-4V interface of hip arthroplasty femoral stem component using multiple linear regression model. A finite element computational model utilising adaptive meshing algorithm via ABAQUS/Standard user subroutine UMESHMOTION is developed. The developed FE model is employed to examine effect of different HAp-Ti-6Al-4V interface mechanical and tribological properties on delamination-fretting wear behaviour. The FE result is utilised to formulate predictive equations for different stress ratio conditions using multiple linear regression analysis. Delamination-fretting wear predictive equations are successfully formulated with significant goodness of fit and reliability as a fast failure prediction tool in HAp coated hip arthroplasty. The robustness of predictive equations is validated as good agreement is noted with actual delamination-fretting wear results. The influence of different mechanical and tribological properties such as delamination length, normal loading, fatigue loading, bone elastic modulus and cycle number under different stress ratio on delamination-fretting wear failure is analysed to formulate failure predictive equations. The formulated predictive equation can serve as a fast delamination-fretting wear failure prediction tool in hip arthroplasty femoral stem component. Limited attempt is done to explore the potential of utilizing multiple linear regression model to predict failures in hip arthroplasty. Thus, present study attempt to formulate delamination-fretting wear failure predictive equation in HAp -Ti-6Al-4V interface of hip arthroplasty femoral stem component using multiple linear regression model.

Design and Fabrication of a 5Ti5Zr5Nb1Sn High‐Entropy Alloy as Metallic Biomedical Material

Herein the present work, the thermodynamic, physical, and mechanical properties of different random solid solution structure models are first calculated based on first‐principles calculation method, and the optimal composition ratio of 5Ti5Zr5Nb1Sn is quickly selected as a new biomedical high‐entropy alloy (HEA) with a low elastic modulus and high strength–ductility balance. Then, 5Ti5Zr5Nb1Sn HEA is prepared by vacuum‐melting method. The microstructure characterization results show that the actual composition of 5Ti5Zr5Nb1Sn HEA corresponds to the calculated target composition, and the HEA consists of two phases BCC1 and BCC2 with distinct color and structure. The compressive yield strength and compressive elongation of the 5Ti5Zr5Nb1Sn HEA are 1171.2 MPa and 29.03%, respectively. The compressive elastic modulus is 22.4 GPa, which is within the range of human bone elastic modulus (10–30 GPa). There are many tiny dimples and small tearing edges in the compression fracture, showing obvious plastic deformation characteristics. The analysis results of potentiodynamic polarization curve show that the corrosion resistance of 5Ti5Zr5Nb1Sn HEA is equivalent to that of pure titanium. Therefore, 5Ti5Zr5Nb1Sn HEA possesses the characteristics of high strength and ductility, low elastic modulus, and excellent corrosion resistance, and has the potential to be used as metallic biomedical materials.

Prediction of brittle fracture propagation behaviour of hydroxyapatite (HAp) coating in artificial femoral stem component

Purpose: This study addresses the brittle fracture propagation behaviour modelling of hydroxyapatite (HAp) coating in artificial femoral stem component. Design/methodology/approach: A simple two dimensional flat-on-flat contact configuration finite element model consisting contact pad (bone), Ti-6Al-4V substrate and HAp coating is employed in static simulation. The HAp coating is modelled as elastic layer with pre-microcrack which assumed to be initiated due to stress singularity. Findings: The study revealed that reducing coating thickness, pre-microcrack length and artificial femoral stem elastic modulus along with increasing bone elastic modulus will result in significant stress intensity factor (SIF) to promote brittle fracture propagation behaviour. Research limitations/implications: The influence of coating thickness, pre-microcrack length, bone and artificial femoral stem elastic modulus on fracture behaviour is examined under different stress ratio using J-integral analysis approach. Practical implications: The proposed finite element model can be easily accommodating different Hap coating thickness, pre-microcrack length, bone and artificial femoral stem elastic modulus to perform detailed parametric studies with minimal costly experimental works. Originality/value: Limited research focussing on brittle fracture propagation behaviour of HAp coating in artificial femoral stem component. Thus, present study analysed the influence of coating thickness, pre-microcrack length, bone and artificial femoral stem elastic modulus on stress intensity factor (SIF) of HAp coating.

Effect of osteoporosis-related reduction in the mechanical properties of bone on the acetabular fracture during a sideways fall: A parametric finite element approach.

The incidence of acetabular fractures due to low-energy falls is increasing among the geriatric population. Studies have shown that several biomechanical factors such as body configuration, impact velocity, and trochanteric soft-tissue thickness contribute to the severity and type of acetabular fracture. The effect of reduction in apparent density and elastic modulus of bone as well as other bone mechanical properties due to osteoporosis on low-energy acetabular fractures has not been investigated. The current comprehensive finite element study aimed to study the effect of reduction in bone mechanical properties (trabecular, cortical, and trabecular + cortical) on the risk and type of acetabular fracture. Also, the effect of reduction in the mechanical properties of bone on the load-transferring mechanism within the pelvic girdle was examined. We observed that while the reduction in the mechanical properties of trabecular bone considerably affects the severity and area of trabecular bone failure, reduction in mechanical properties of cortical bone moderately influences both cortical and trabecular bone failure. The results also indicated that by reducing bone mechanical properties, the type of acetabular fracture turns from elementary to associated, which requires a more extensive intervention and rehabilitation period. Finally, we observed that the cortical bone plays a substantial role in load transfer, and by increasing reduction in the mechanical properties of cortical bone, a greater share of load is transmitted toward the pubic symphysis. This study increases our understanding of the effect of osteoporosis progression on the incidence of low-energy acetabular fractures. The osteoporosis-related reduction in the mechanical properties of cortical bone appears to affect both the cortical and trabecular bones. Also, during the extreme reduction in the mechanical properties of bone, the acetabular fracture type will be more complicated. Finally, during the final stages of osteoporosis (high reduction in mechanical properties of bone) a smaller share of impact load is transferred by impact-side hemipelvis to the sacrum, therefore, an osteoporotic pelvis might mitigate the risk of sacral fracture.

Manufacturability of lattice structures fabricated by laser powder bed fusion: A novel biomedical application of the beta Ti-21S alloy

Additively manufactured lattice structures of titanium alloys, especially Ti6Al4V, are widely studied for their use in bone replacement implants. The porous nature of these lattice structures reduces the effective elastic modulus and hence can be matched to that of bone, in order to reduce stress shielding effects and allow long-term bone in-growth. The typical Ti6Al4V material manufactured by laser powder bed fusion requires post-process heat treatment to remove residual stresses and improve the ductility. A recently developed novel β-Ti alloy for laser powder bed fusion is of interest in this application due to its lower bulk elastic modulus, closer to that of bone compared to bulk Ti6Al4V. This implies that lattice structures need less porosity, improving the structural integrity while still matching the bone elastic modulus. The bulk β-Ti alloy also has high ductility without any post-process heat treatment, improving fatigue performance and reducing the number of steps involved in the process. In this work, the manufacturability of lattice structures in this new β-Ti alloy is investigated. The focus in this work is on coupon lattice samples with simple geometries and their mechanical and physical characterization, allowing an assessment of manufacturability for future lattice implants of this β-Ti alloy.

Mechanical, Corrosion, and Ion Release Studies of Ti-34Nb-6Sn Alloy with Comparable to the Bone Elastic Modulus by Powder Metallurgy Method

The development of a Ti-34Nb-6Sn alloy by the powder metallurgy method, employing two different compaction conditions, A (100 MPa) and B (200 MPa), was carried out. To evaluate the feasibility of the Ti-34Nb-6Sn alloy as an implant biomaterial, microstructural and mechanical characterizations, as well as corrosion susceptibility and ion release tests, were performed. Results indicated microstructures dominated by the presence of β-Ti phase and a lower percentage of α-Ti and Nb phases. The porosity percentage decreased when the compaction pressure increased. Both conditions presented a good match between the elastic moduli of the alloy (14.0 to 18.8 GPa) and that reported for the bone tissue. The Ti, Nb and Sn ions released for both compaction conditions were within the acceptable ranges for the human body. Condition B showed higher corrosion resistance in comparison with condition A. Based on the obtained results, the produced porous Ti-34Nb-6Sn alloys are feasible materials for orthopedic implant applications.