Magnesium Alloy Implants Research Articles

In Vivo Study of Organ and Tissue Stability According to the Types of Bioresorbable Bone Screws

Biodegradable material, such as magnesium alloy or polylactic acid (PLA), is a promising candidate for orthopedic surgery. The alloying of metals and the addition of rare earths to increase mechanical strength are still questionable in terms of biosafety as absorbent materials. Therefore, the purpose of this study is to understand the effect of substances due to the degradation of various biodegradable substances on organs in the body or surrounding tissues. A total of eighty male Sprague−Dawley rats were selected for this study, and the animals were divided into four groups. Each of the three experimental groups was implanted with magnesium alloy, polymer, and titanium implants; the control group only drilled into the cortical bone. Serum assay, micro-CT, hematoxylin and eosin staining, immunoblotting, and real-time PCR were evaluated. There was no significant difference between the two groups of magnesium alloy and polymer in serum assay, but micro-CT analysis confirmed that magnesium alloy degrades faster than polymer, and histological examination showed a strong inflammatory response in the early stages, which was similarly observed in immunoblotting and real-time PCR. Our findings show that there was no toxicity due to the degradation of the biodegradable material, and the difference in each inflammatory response is thought to be determined by the rate of degradation in the body.

Enhancement of PEO-coated ZK60 Mg alloy: Curcumin-enriched mesoporous silica and PLA/bioglass for antibacterial properties, bioactivity and biocorrosion resistance

The corrosion resistance and antibacterial properties of ZK60 magnesium alloy implants have been enhanced via Plasma Electrolytic Oxidation (PEO) and electrospinning techniques. A robust, porous oxide coating was created on the ZK60 alloy using the PEO process, with characterization performed via SEM and XRD. Improved corrosion resistance of the PEO-coated samples was demonstrated through electrochemical analyses, including EIS and polarization tests. In addition to the PEO treatment, composite electrospun nanofibrous coatings were developed, incorporating curcumin-loaded mesoporous silica nanoparticles and bioactive glass. The electrospun nanofibers, which exhibited a diameter of 350 nm without beads, were characterized by Dynamic Light Scattering, Zeta Potential, Infrared Spectroscopy, BET, and XRD, confirming a curcumin loading of 10 wt%. Significant antibacterial activity against Escherichia coli and Staphylococcus aureus was shown by these fibers, and high bioactivity was observed after 14 days of immersion in simulated body fluid (SBF). The combination of PEO coatings and electrospun nanofibers highlights an enhancement in both corrosion resistance and antibacterial properties for implant applications.

Surface transformed magnesium alloy: Investigating the in-vitro degradation consequences of rare-earth bioactive coatings

Rare-earth elements dominate both the industrial and the medical fields. Recent advancements in assisted bone healing implant research have sparked a revolution emphasising the exploration of new materials and customized applications with simplified methodology. In line with this trend, our study introduces an approach by applying a rare-earth element, terbium, as a coating on magnesium alloy implants. The in-vitro behaviour of the coated implants was systematically evaluated based on the duration of the coating formation and optimised. The TCC-30 coating started to degrade beyond the optimised duration of conversion. The resulting coating exhibited a distinctive nanolamellar structure on the surface, which transformed into a flower-like morphology as it matured. The chemical profiling of the coating with XPS confirmed the presence of elements including Tb, O and Mg. The mineralizing ability was examined with simulated body fluid (SBF) and Dulbecco's Modified Eagle Medium (DMEM) was found to possess nano-agglomerate structure in the form of clusters and coral-like morphology with nano petals structure, respectively. Further exploration of the biological behaviour including monitoring cell attachment and proliferation demonstrated enhancement. This innovative approach holds promise for enhancing the performance and biocompatibility of magnesium alloy implants, marking a significant stride in the ongoing evolution of assisted bone healing technologies.

Optimising Mg-Ca/PLA Composite Filaments for Additive Manufacturing: An Analysis of Particle Content, Size, and Morphology.

Low-temperature additive manufacturing of magnesium (Mg) alloy implants is considered a promising technique for biomedical applications due to Mg's inherent biocompatibility and 3D printing's capability for patient-specific design. This study explores the influence of powder volume content, size, and morphology on the mechanical properties and viscosity of polylactic acid (PLA) matrix composite filaments containing in-house-produced magnesium-calcium (Mg-Ca) particles, with a focus on their application towards low-temperature additive manufacturing. We investigated the effects of varying the Mg-Ca particle content in a PLA matrix, revealing a direct correlation between volume content and bending strength. Particle size analysis demonstrated that smaller particles (D50: 57 μm) achieved a bending strength of 63.7 MPa, whereas larger particles (D50: 105 μm) exhibited 49.6 MPa at 20 vol.%. Morphologically, the filament containing spherical particles at 20 vol.% showed a bending strength that was 11.5 MPa higher than that of the filament with irregular particles. These findings highlight the critical role of particle content, size, and shape in determining the mechanical and rheological properties of Mg-Ca/PLA composite filaments for use in material extrusion additive manufacturing.

Peri-articular elbow fracture fixations with magnesium implants and a review of current literature: A case series.

In recent years, the use of Magnesium alloy implants have gained renewed popularity, especially after the first commercially available Conformité Européenne approved Magnesium implant became available (MAGNEZIX® CS, Syntellix) in 2013. To document our clinical and radiographical outcomes using magnesium implants in treating peri-articular elbow fractures. Our paper was based on a retrospective case series design. Intra-operatively, a standardized surgical technique was utilized for insertion of the magnesium implants. Post - operatively, clinic visits were standardized and physical exam findings, functional scores, and radiographs were obtained at each visit. All complications were recorded. Five patients with 6 fractures were recruited (2 coronoid, 3 radial head and 1 capitellum). The mean patient age and length of follow up was 54.6 years and 11 months respectively. All fractures healed, and none exhibited loss of reduction or complications requiring revision surgery. No patient developed synovitis of the elbow joint or suffered electrolytic reactions when titanium implants were used concurrently. Although there is still a paucity of literature available on the subject and further studies are required, magnesium implants appear to be a feasible tool for fixation of peri-articular elbow fractures with promising results in our series.

CORROSION PREDICTION OFMAGNESIUM IMPLANT USING MULTISCALE MODELING BASED ON MACHINE LEARNING ALGORITHMS

Significant thoughtful research is really necessary to improve the patient outcomes and reduce the social and financial burdens associated with implant failure. The primary focus of the researchers is to minimize the major implant failure due to corrosion attributed to making orthopedic surgery safer and more effective. Hence, a critical review has been done in this present article on the various multiscale modelings based on machine learning algorithms (MLAs) to predict the corrosion behavior of magnesium (Mg) alloy implants. According to the best of the authors' knowledge, all the available multiscale modelings tools, such as artificial neural network (ANN), least absolute shrinkage and selection operator (LASSO) regression model, multiple linear regression and random forest regression (RFR) models, etc., are methodically presented and discussed in detailed here for the prediction of corrosion mechanism. Subsequently, various multiscale model tools and assessment metrics for models have been thoroughly compared and criticized for better understanding and optimizing of the corrosion behavior of implants. The comparison indicates that the RFR model may be the best option, whereas the LASSO regression model and ANNs show inefficient performance for the prediction of corrosion behavior. Apart from the multiscale modeling approach, the authors have also explored the physiology and properties of alloys, bone implant, immune and tissue system, and the corrosion control mechanisms of Mg alloy. Finally, the present review on multiscale modeling approach and assessment metrics models will enhance the knowledge and understanding of the corrosion behavior of Mg alloy for implant application.

Design and characterization of β-tricalcium phosphate-based self-passivating coatings on magnesium alloys.

Background: Magnesium alloys degrade rapidly in salt solutions, which limits their use without passivating treatments. AZ31 alloy is particularly promising for implant applications owing to its biodegradability and mechanical properties, necessitating effective corrosion-resistant coatings. Aim: In this study, a self-passivating reactive coating was designed and evaluated for AZ31 magnesium alloy plates using β-tricalcium phosphate (TCP) to enhance corrosion resistance and biocompatibility. Methods: Solutions of TCP, trisodium citrate, magnesium nitrate, hydroxyethyl cellulose (HEC), and sodium chloride were used to dip-coat AZ31 plates. The coated samples were immersed in 3.5 wt% NaCl solution. Phase evolution was analysed using gravimetry, X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The biological response of the coated samples was evaluated through MTT and resazurin assays. Results: The coating formed a stable TCP/HEC layer that gradually dissolved over two weeks, converting the surface to magnesium hydroxide, magnesium oxychloride, and magnesium phosphate phases. The formation of brucite, responsible for passivation in the long term, was observed. The coating effectively prevented excessive magnesium oxychloride formation and stabilised magnesium hydroxide after one week. Biological characterization indicated that the coating on AZ31 is safe on the Saos-2 and L929 cell lines. Conclusion: The TCP-based coating enhances the corrosion resistance of AZ31 alloy in salt solutions, promoting passivating phases and limiting corrosive products, thereby ameliorating biocompatibility issues. This coating demonstrates substantial potential for extending the longevity and functionality of magnesium alloy implants.

The effect of addition of K2ZrF6 on the structures and properties of AZ31 magnesium alloy MAO coating

It is a challenge to improve the corrosion rate and blood compatibility of biomedical magnesium alloy implants in human body. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were used to study the Properties of K2ZrF6 modified AZ31 magnesium alloy composite coating. The corrosion behavior of the sample in simulated body fluid (SBF) was evaluated by hydrogen evolution corrosion, potentiodynamic polarization cur ve and electrochemical impedance spectroscopy. The results show that the corrosion resistance of magnesium alloy is significantly improved by composite coating. The wettability test shows that K2ZrF6 greatly improves the biocompatibility of MAO coating on magnesium alloy. The hemolysis test shows that the composite coating makes magnesium alloy have low hemolysis rate. The increase of PH value and magnesium ion concentration in solution caused by corrosion of magnesium alloy can be adjusted by adding K2ZrF6. The corrosion resistance mechanism of MAO coating on K2ZrF6 modified magnesium alloy was discussed. In this experiment, the optimum amount of K2ZrF6 is 4 g/L.

STUDY OF THE INFLUENCE OF SILVER ALLOYING ON THE MICROSTRUCTURE AND PROPERTIES OF MAGNESIUM ALLOY NZ30K FOR IMPLANTS IN OSTEOSYNTHESIS

Purpose. Study of the influence of silver alloying of magnesium alloy NZ30K on its mechanical properties for use in the manufacture of biodegradable implants. Research methods. The tensile strength and relative elongation of the samples were determined on a P5 tensile machine at room temperature. The microstructure of the samples was studied using a “Carl Zeiss” optical electron microscope using the “Observer.D1m” software. Samples were used after etching with a reagent containing 1 % nitric acid, 20 % acetic acid, 19 % distilled water, and 60 % ethylene glycol. Fractographic analysis of sample fractures was performed on a JSM-6360LA scanning electron microscope. The phase analysis of the structural components of magnesium alloys was studied using an electron microscope – a microanalyzer with an energy dispersive attachment РEMMA 202М and РЕМ 16I. Research on biocorrosion was carried out by keeping the samples in a solution of gelofusin – an artificial blood substitute for 2, 4, 6 weeks, using a TC-20 MICROmed thermostat. Results. The study showed that silver was a part of the complex alloyed intermetallic phases, which were additional crystallization centers. In this case, the average grain size decreases by almost three times compared to the original alloy. It was found that the optimal set of properties is achieved by the introduction of 0.1 % Ag, while the tensile strength increases by 7.9 % and the relative elongation almost doubles. It was found that the magnesium alloy with silver (0.1 %) slows down biocorrosion processes and helps to maintain a high level of tensile strength (σB = 205 MPa) after 6 weeks of exposure to a solution of helofusine. Thus, silver is a promising material for improving the structure and increasing the mechanical properties of biodegradable magnesium alloy implants. Scientific novelty. The silver content for alloying the NZ30K alloy was determined to be 0.1 % Ag, which forms the optimal ratio of strength and ductility, grain structure refinement, and slowing down biocorrosion processes. Practical value. NZ30K alloy with the addition of 0.1 % silver is promising for use in the manufacture of implants. The studied alloy provides the required level of properties until complete fracture consolidation.

Composite Nanocoatings of Biomedical Magnesium Alloy Implants: Advantages, Mechanisms, and Design Strategies.

The rapid degradation of magnesium (Mg) alloy implants erodes mechanical performance and interfacial bioactivity, thereby limiting their clinical utility. Surface modification is among the solutions to improve corrosion resistance and bioefficacy of Mg alloys. Novel composite coatings that incorporate nanostructures create new opportunities for their expanded use. Particle size dominance and impermeability may increase corrosion resistance and thereby prolong implant service time. Nanoparticles with specific biological effects may be released into the peri-implant microenvironment during the degradation of coatings to promote healing. Composite nanocoatings provide nanoscale surfaces to promote cell adhesion and proliferation. Nanoparticles may activate cellular signaling pathways, while those with porous or core-shell structures may carry antibacterial or immunomodulatory drugs. Composite nanocoatings may promote vascular reendothelialization and osteogenesis, attenuate inflammation, and inhibit bacterial growth, thus increasing their applicability in complex clinical microenvironments such as those of atherosclerosis and open fractures. This review combines the physicochemical properties and biological efficiency of Mg-based alloy biomedical implants to summarize the advantages of composite nanocoatings, analyzes their mechanisms of action, and proposes design and construction strategies, with the purpose of providing a reference for promoting the clinical application of Mg alloy implants and to further the design of nanocoatings.

Composite bone-implant engineered with magnesium and variable degradation for orthopaedics

Metallic biomaterials are suitable for load-bearing scaffolds, and magnesium (Mg) alloy is the most preferable because of its mechanical properties are comparable to those of hard tissue (bone). The most important characteristic of an implant is its biocompatibility and Mg fully satisfies this standard. Mg is also biodegradable, thereby avoiding the need for secondary surgery. An uncontrollable degradation rate is one of the most significant limitations of magnesium-based implants, which hinders their applications in bone tissue engineering. Hydroxyapatite (HAP), a bioactive material, was incorporated into a magnesium metal matrix as a catalyst for enhancing bone tissue regeneration. Porosity in the scaffold could serve as a conduit for nutrients and also aids in the scaffold's weight reduction. This study investigated the effect of selective alloying elements (Ca, Zn, and Fe) on the biodegradability of scaffolds. Powder metallurgy was used to produce the magnesium alloy scaffolds. A calculated quantity of porogen particles, carbamide (urea), was incorporated into the Mg-Ca-Zn-Fe matrix in order to achieve 30% and 50% porosity. Due to the formation of Mg-Ca-Zn-Fe intermetallic compounds, the current study establishes that Mg alloy-based samples exhibit favorable biodegradation behavior. After seven days of immersion, the pH of the immersion liquid had also been found to have stabilized. Consequently, the observations suggest that the biodegradation behavior of bone implants could be modified by developing composite porous magnesium alloy implants.

In Vivo Degradation Behavior of Magnesium Alloy for Bone Implants with Improving Biological Activity, Mechanical Properties, and Corrosion Resistance.

This study aimed to establish a surface modification technology for ZK60 magnesium alloy implants that can degrade uniformly over time and promote bone healing. It proposes a special micro-arc oxidation (MAO) treatment on ZK60 alloy that enables the composite electrolytes to create a coating with better corrosion resistance and solve the problems of uneven and excessive degradation. A magnesium alloy bone screw made in this way was able to promote the bone healing reaction after implantation in rabbits. Additionally, it was found that the MAO-treated samples could be sustained in simulated body-fluid solution, exhibiting excellent corrosion resistance and electrochemical stability. The Ca ions deposited in the MAO coating were not cytotoxic and were beneficial in enhancing bone healing after implantation.

Recent research advances on corrosion mechanism and protection, and novel coating materials of magnesium alloys: a review.

Magnesium alloys have achieved a good balance between biocompatibility and mechanical properties, and have great potential for clinical application, and their performance as implant materials has been continuously improved in recent years. However, a high degradation rate of Mg alloys in a physiological environment remains a major limitation before clinical application. In this review, according to the human body's intake of elements, the current mainstream implanted magnesium alloy system is classified and discussed, and the corrosion mechanism of magnesium alloy in vivo and in vitro is described, including general corrosion, localized corrosion, pitting corrosion, and degradation of body fluid environment impact etc. The introduction of methods to improve the mechanical properties and biocorrosion resistance of magnesium alloys is divided into two parts: the alloying part mainly discusses the strengthening mechanisms of alloying elements, including grain refinement strengthening, solid solution strengthening, dislocation strengthening and precipitation strengthening etc.; the surface modification part introduces the ideas and applications of novel materials with excellent properties such as graphene and biomimetic materials in the development of functional coatings. Finally, the existing problems are summarized, and the future development direction is prospected.

Вплив легування золотом на структуру та властивості магнієвого сплаву NZ30K

In this work, was conducted research to improve the structure and properties of cast magnesium alloy NZ30K by doping with gold, for use in osteosynthesis. Gold is a safe alloying element for the human body. The effect of alloying 0.05%, 0.1% and 0.2% Au of magnesium alloy NZ30K was investigated in this work. A qualitative and quantitative assessment of the structural components of the alloy was carried out. It was shown that gold was part of the complex doped intermetallic phases, which were additional centers of crystallization. It was established that the optimal complex of properties is achieved by introducing 0.1%Au. At the same time, the average grain size is reduced by 52.4% compared to the original alloy. It was found that for the NZ30K+0.1%Au alloy, simultaneous increase in the strength limit by 7.8% and increase in the relative elongation by almost two times was observed. It was investigated the possibility of using a biodegradable magnesium alloy in the manufacture of fixators during osteosynthesis, biocorrosion processes. It was found that the addition of 0.1% Au slows down the biocorrosion processes and contributes to maintaining a high level of strength limit (σB = 200MPa) after exposure for 6 months in a gelofusin solution. Therefore, gold is a promising material for improving the structure and improving the properties of biodegradable magnesium alloy implants. Keywords: NZ30K, gold, biodegradable implants, microstructure, X-ray spectral microanalysis, mechanical properties, biocorrosion.

Enhanced abrasive-mixed-µ-EDM performance towards improved surface characteristics of biodegradable Mg AZ31B alloy

The non-degradable metallic implants, such as bone screws, often act as the source of dysfunction and harmful corrosion products in the aqueous environment inside the human body. Many of these implants are fixed either temporarily or permanently into the human body, and therefore, both need to match tight tolerances with a remarkably finished surface to eradicate burrs or striations. In this regard, the new generation of degradable magnesium (Mg) alloy implants with excellent osseointegration and low elasticity (like that of human bone), minimizing stress shielding, have been identified as potential candidates to challenge surgical procedures reintervention. However, the biological response of an implant toward the cells in vivo can be predominantly regulated by modifying the surface chemistry, morphology, and corrosion characteristics. Powder or abrasive-mixed-micro-electric discharge machining (A-M-µ-EDM) is gaining attention for executing precision machining and achieving a simultaneous surface modification on micro-manufactured surfaces, suitable for clinical applications. Therefore, the present research aimed at improving the surface characteristics of Mg AZ31B alloy via an augmented performance of A-M-µ-EDM by adopting copper and brass-micro-electrodes (C-µ-E and B-µ-E) in association with distinct abrasive particle concentrations (APCs: 0, 1.5, 3, 4.5, and 6g/l) of bioactive zinc abrasives. To enhance the A-M-µ-EDM capabilities, the experiments were designed with a one-variable-at-a-time (OVAT) strategy, and the trial runs were conducted using different combinations of µ-electrodes and APCs. The superior performance of A-M-µ-EDM was noticed with the fusion of C-µ-E and 3g/l APC in terms of minimum machining time (MT) and dimensional deviation (DD). The additional outcomes of this work reported favorable improvements in surface morphology, chemistry, topography, wettability, microhardness, and corrosion resistance on the A-M-µ-EDMed sample of interest.

Bone Remodeling Interaction with Magnesium Alloy Implants Studied by SEM and EDX.

The development direction of bioresorbable fixing structures is currently very relevant because it corresponds to the priority areas in worldwide biotechnology development. Magnesium (Mg)-based alloys are gaining high levels of attention due to their promising potential use as the basis for fixating structures. These alloys can be an alternative to non-degradable metal implants in orthopedics, maxillofacial surgery, neurosurgery, and veterinary medicine. In our study, we formulated a Mg-2Zn-2Ga alloy, prepared pins, and analyzed their biodegradation level based on SEM (scanning electron microscopy) and EDX (energy-dispersive X-ray analysis) after carrying out an experimental study on rats. We assessed the resorption parameters 1, 3, and 6 months after surgery. In general, the biodegradation process was characterized by the systematic development of newly formed bone tissue. Our results showed that Mg-2Zn-2Ga magnesium alloys are suitable for clinical applications.

Haematological and Biochemical Parameters of Blood in Patients after BIOS of the Tibia using Bioinert and Biodegradable Implants based on Magnesium Alloy MA-10

Nowadays, the search for new artificial materials to replace damaged tissues and organs is becoming increasingly important. Biodegradable materials occupy an honorable place among medical materials. Depending on the purpose, biodegradable implants should be gradually replaced by living tissue and function over a given period of time, as well as not have a negative impact on surrounding tissues and the body as a whole. Magnesium-based alloys are considered promising. Clinical studies of the dynamics of a number of key biochemical parameters that characterize the reactive response and regenerative processes in the body are of scientific and practical importance. The aim of the research was to study the laboratory - biochemical parameters of blood in patients after BIOS of the tibia using bioinert and biodegradable implants based on magnesium alloy MA-10 Materials and methods. 36 patients with tibial fractures were operated in the traumatology department of MNCE “CH of Emergency and Urgent Medical Aid” in Zaporizhzhia. After closed repositioning, the tibial BIOS was performed using biodegradable alloy screws. Blood sampling for biochemical and cytological studies was performed before and in 2, 4 weeks, 2 and 4 months after surgery. Biodegradable magnesium alloy MA-10 (TU U 24.4-14307794-270: 2018) certified for use in medicine. Results. The study of the total bilirubin dynamics in blood plasma showed that the maximum values of the indicator accompany the acute period of the pathological process. From the second week, slight fluctuations in α-amylase activity were detected, which is most likely due to the energetic support of the inflammatory process and the regeneration of damaged tissues. The use of magnesium alloy for the manufacture of screws showed stable enzyme activity for 4 weeks. In the group of patients who used magnesium alloy implants immediately after surgery, there was a significant (p≤0.05) increase in AST / ALT by 44%, compared with the initial value of the de Ritis coefficient, not by increasing the activity of AST, but by reducing activity ALT. The undulating dynamics of ESR, fibrinogen B and total bilirubin in the blood of patients of both groups reflects the stages of the reparative process. Conclusions. The bioinertness and expediency of using implants made of biodegradable magnesium alloy MA-10 in the dynamic BIOS for diaphyseal fractures of the tibia are substantiated.

Toward understanding in vivo corrosion: Influence of interfacial hydrogen gas build-up on degradation of magnesium alloy implants.

Limited material transport, causing gas cavities formation, is commonly observed during the degradation of magnesium implants, yet its effects on corrosion are not understood. Herein, a bespoke cell was designed, allowing for the incorporation of an additional agarose layer above the corroding magnesium sample. This design replicates the limited material transport in vitro and enables us to understand its influence on corrosion of magnesium alloys. This work investigated the influence of varying thickness of agarose (0-0.9 mm) on the corrosion of Mg-Zn-Zr magnesium alloy maintained at 37°C in phosphate-buffered saline (PBS). The introduction of agarose slowed transport of material away from the corroding magnesium surface, including the evolved hydrogen forming a gas cavity. It has been found that an initial increase in the agarose thickness (or the reduction in material transport) of 0.3 mm leads to an increase in the corrosion rate of the magnesium alloy by 62%. However, with a further increase in agarose thickness from 0.3 to 0.9 mm, the corrosion rate decreases by 37%. This observation has been attributed to the accumulation of, and competition between, chloride and hydroxide ions near the alloy's surface. In the presence of materials barrier, hydrogen measurement is no longer a reliable method for the measurement of corrosion rates. This study underscores the importance of the consideration of limited material transport during the in vitro corrosion tests of biomedical implants.

Effect of extrusion parameters on degradation of magnesium alloys for bioimplant applications: A review

Magnesium alloys, as a new generation temporary biomaterial, deserve the desirable biocompatibility and biodegradability, and also contribute to the repair of the damaged bone tissues. However, they do not possess the required corrosion resistance in human body fluid. Hot mechanical workings, such as extrusion, influence both the mechanical properties and bio-corrosion behavior of magnesium alloys. This review aims to gather information on how the extrusion parameters (extrusion ratio and temperature) influence the bio-corrosion performances of magnesium alloys. Their effects are mainly ascribed to the alteration of extruded alloy microstructure, including final grain size and uniformity of grains, texture, and the size, distribution and volume fraction of the second phases. Dynamic recrystallization and grain refinement during extrusion provide a more homogeneous microstructure and cause the formation of basal texture, resulting in improved strength and corrosion resistance of magnesium alloy. Extrusion temperature and extrusion ratio are reported as the influential factors in the degradation. The reports reveal that the increase in extrusion ratio and/or the reduction in extrusion temperature cause a decrease in the final grain size, leading to intensification of basal texture, in parallel side of the samples with extrusion line, and to lower volume fraction and size of precipitates in magnesium alloys. These all lead to improving the bio-corrosion resistance of the magnesium alloy implants.

Biocompatibility evaluation of peo-treated magnesium alloy implants placed in rabbit femur condyle notches and paravertebral muscles

BackgroundMagnesium alloys have been receiving much attention for use in biodegradable metal implants because of their excellent mechanical properties and biocompatibility. However, their rapid breakdown and low bioactivity can cause the implant to lose mechanical integrity before the bone is completely healed. Moreover, hydrogen gas released during degradation can significantly delay the tissue regeneration process. To solve the instability of magnesium alloys, Zn and Ca can be added to improve the mechanical properties and biocompatibility. One other way to improve the mechanical properties of Mg is plasma electrolytic oxidation (PEO), which provides a dense, thick ceramic-like coating on the Mg surface. In this study, high-purity Mg was selected as the control, and Mg-1wt%Zn-0.1wt%Ca alloy and PEO-treated Mg-1wt%Zn-0.1wt%Ca alloy were selected as the test materials; the results of radiographic and histological analyses of their biocompatibility are reported herein.Materials and methodNineteen New Zealand white rabbits were used in the study. Rod-bars (Ø2.7 × 13.6 mm) were placed on both paravertebral muscles, and cannulated screws (Ø2.7x10mm) were placed on both femur condyle notches. Each animal was implanted in all four sites. X-rays were taken at 0, 2, 4, 8, and 12 weeks, micro-CT, and live-CT were taken at 4, 8, and 12 weeks. At weeks 4, 8, and 12, individuals representing each group were selected and sacrificed to prepare specimens for histopathological examination.ResultThe results confirm that in vivo, Mg-1wt%Zn-0.1wt%Ca alloy had higher corrosion resistance than high-purity Mg and safely degraded over time without causing possible side effects (foreign body or inflammatory reactions, etc.). In addition, PEO treatment of Mg-1wt%Zn-0.1wt%Ca alloy had a positive effect on fracture recovery by increasing the bonding area with bone.ConclusionOur results suggest that PEO treatment of Mg-1wt%Zn-0.1wt%Ca alloy can be a promising biomaterials in the field of various clinical situations such as orthopedic and maxillofacial surgerys.