Orthopaedic Alloys Research Articles

Unraveling the Corrosion of the Ti–6Al–4V Orthopedic Alloy in Phosphate-Buffered Saline (PBS) Solution: Influence of Frequency and Potential

This paper addresses the interplay between electrical fields in the human body and the corrosion behavior of Ti-6Al-4V alloy, a prevalent orthopedic material. The study investigates the impact of alternative electrical signals at different frequencies on the alloy’s electrochemical behavior in a simulated body environment. The human body always has natural sinusoidal potential due to, e.g., heart palpitations and brain/nervous system activities. Ignoring such natural activities may lead to underestimating the corrosion performance of the Ti-6Al-4V alloy in the body. By analyzing anodic and cathodic responses and the net faradaic current induced by alternating current potential, the research sheds light on the influence of electrical fields on corrosion rates. Understanding these dynamics could lead to improved implant materials, mitigating corrosion-related challenges and enhancing implant performance over the long term. Results of this work indicated that frequent oxidation and reduction at certain frequencies may induce corrosion and hinder biomimetic apatite formation, impacting osseointegration. Natural alternative currents in the body affect the corrosion performance of Ti-based implant alloys, highlighting the need for consideration in biomedical applications.

In Vitro Inflammatory Cell-Induced Corrosion Using a Lymphocyte and Macrophage Coculture

BackgroundCobalt-chromium-molybdenum (CoCrMo) and titanium alloys have been used for orthopaedic implants for decades. However, recent evidence has shown that inflammatory cell-induced corrosion (ICIC) can damage these metal alloys. This study aimed to investigate the mechanisms of ICIC by coculturing macrophages with lymphocytes. We hypothesized that macrophages would be able to alter the surface oxide layer of CoCrMo and titanium alloy (Ti6Al4V) disks, with greater oxide layer damage occurring in groups with a coculture compared to a macrophage monoculture and in groups with inflammatory activators compared to nonactivated groups. MethodsMurine macrophages were cultured on American Society for Testing and Materials F1537 CoCrMo and F136 Ti6Al4V disks for 30 days and activated with interferon gamma and lipopolysaccharide. Interferon gamma and lipopolysaccharide were added to the culture medium to simulate local inflammation. Macrophages were either cultured alone or in a coculture with T helper lymphocytes. After the 30-day experiment, scanning electron microscopy was used to examine the disk surfaces, and oxide levels were found using energy dispersive x-ray spectroscopy. ResultsPitting features consistent with previous reports of ICIC were found on disks cultured with cells. Both CoCrMo and Ti6Al4V disks had significantly lower oxide levels in all groups with cells compared to control groups with no cells (P < .01). Additionally, CoCrMo disks had significantly lower oxide levels when cultured with activated macrophages and lymphocytes compared to nonactivated macrophages alone (P < .001), activated macrophages alone (P < .01), and nonactivated macrophages and lymphocytes (P < .05). No differences in the oxide levels were found among the Ti6Al4V groups. ConclusionsThis study demonstrates the ability of macrophages to alter the surface chemistry of commonly used orthopaedic alloys. We found that the addition of lymphocytes and a simulated local inflammatory response may contribute to the ICIC of CoCrMo implants.

Applying Nanocomposite Coatings to Improve Orthopedic Alloys by Using Multiple Flame Spray

Applying Nanocomposite Coatings to Improve Orthopedic Alloys by Using Multiple Flame Spray

Metal hypersensitivity and pro-inflammatory cytokine production in patients with failed orthopedic implants: A case-control study

Orthopedic implants heal well without complications in most patients but fail for unclear reasons in some individuals. This study determined the relevance of metal hypersensitivity in patients with failed orthopedic implants and those requiring orthopedic implant surgery. The study included 35 patients with failed orthopedic implants and 15 subjects scheduled for orthopedic implant surgery. The production of selected pro-inflammatory cytokines was measured in patients with failed orthopedic implants. Metal hypersensitivity was measured in all subjects using the MELISA® test. Of common metals in orthopedic alloys, the patients with failed orthopedic implants responded most frequently to nickel, chromium, titanium, iron, and molybdenum. Hypersensitivity to metals found in implants was measured in 40% of patients with failed implants. The study also showed that titanium exposure in patients with titanium hypersensitivity might lead to implant failure. Metal hypersensitivity testing should be offered to patients before surgery to minimize the risk of implant failure.

Fatigue life assessment of orthopedic plates made of Ti6Al4V

This study is aimed to analyse fatigue life of orthopedic plates due to cracks initiated in the stress concentration areas. Material used for this analysis was typical orthopedic alloy, Ti-6Al-4V, strong but not very ductile, meaning also sensivite to cracking, as indicated by its mechanical properties, such as tensile strength, impact toughness and fracture toughness, as well as by high fatigue crack rate, all of them tested and analysed here. Extended finite element method (XFEM) in ANSYS software was used for simulating the fatigue crack growth in 5 orthopedic plates with different geometries. Results for crack length and stress intensity factor vs. number of cycles are given, indicating plate D as the best option regarding residual life. Crack paths are analysed in all 5 plates to explain such a behaviour, indicating benefits of initial crack growth into length, followed by growth into depth. Also, the effect of geometry of plates is considered to explain differences in life predictions for 5 different plates.

The effect of hypochlorous acid on the tribocorrosion of CoCrMo/Ti-6Al-4V bearing couples.

Mechanically assisted corrosion (MAC) of metallic orthopedic alloys is a consequence of the use of modular devices where opposing metal surfaces are tightly mated and loaded at the taper junction. MAC processes are affected by material surface characteristics and local solution chemistry. During inflammation, active immune cells may generate reactive oxygen species (such as hypochlorous acid [HOCl]) adjacent to surfaces undergoing micromotion, which may affect the tribocorrosion behavior of an implanted device. This study investigated the fretting current response of CoCrMo/Ti-6Al-4V couples in a pin-on-disk apparatus utilizing HOCl solutions as a proxy for a severe inflammatory environment. Testing in 1 and 5 mM HOCl solutions were shown to generate a threefold and fivefold increase (p < 0.01), respectively, in fretting currents over pH7.4 phosphate-buffered saline control conditions. Fretting currents were shown to be dependent on the energy dissipated during fretting and the concentration of HOCl where the currents within a single HOCl concentration were linearly dependent of energy dissipated, but different HOCl levels shifted (increased and then decreased) fretting currents with concentration. Fretting currents, governed by regrowth of an abraded oxide film, were affected by the oxidative power of the solution, which caused positive shifts in open circuit potential and likely resulted in a thicker oxide for 1 mM and 5 mM and fell with 30 mM. Small amounts of HOCl release within a joint may result in increased release of tribocorrosion products such as oxide particles.

Synergistic interactions between wear and corrosion of Ti-16Mo orthopedic alloy

In this study, corrosion, wear, and tribocorrosion of Ti-16Mo alloy manufactured by powder metallurgy (PM) in phosphate-buffered saline are investigated. The results indicate that the corrosion rate of Ti-16Mo alloy increases about 100 times from 0.00009 mm/yr to 0.00851 mm/yr under the tribocorrosion condition. Also, corrosion accelerates wear loss, and wear increment rate due to the corrosion (4.7715 mm/yr) of Ti-16Mo alloy is about 40% of pure mechanical wear rate (11.78 mm/yr). Compared with as-cast pure Ti (23.70999 mm/yr) and Ti-6Al-4 V (17.12003 mm/yr), Ti-16Mo alloy exhibits the lowest materials loss of 16.56001 mm/yr making it become a promising alloy for bone-tissue applications.

Effects of Mo content on corrosion and tribocorrosion behaviours of Ti-Mo orthopaedic alloys fabricated by powder metallurgy

Effects of Mo content on corrosion and tribocorrosion of Ti-(8–20)Mo alloys fabricated by powder metallurgy (PM) were investigated. With a higher Mo content, the Ti-Mo alloys showed an increased corrosion resistance, and correspondingly their tribocorrosion resistance presented an initial increase but a subsequent decrease. Ti-16Mo alloy possessed the lowest wear rate of 1.0 × 10−3 mm3/m•N under tribocorrosion condition, which was about 30 % of that of as-cast pure Ti (3.3 × 10-3 mm3/m•N) and 91 % of that of Ti-6Al-4 V alloy (1.1 × 10-3 mm3/m•N), respectively. The highest tribocorrosion resistance and adequate corrosion resistance make the Ti-16Mo alloy a promising candidate for orthopedic applications.

Role of aging induced α precipitation on the mechanical and tribocorrosive performance of a β Ti-Nb-Ta-O orthopedic alloy.

A low modulus β Ti-Nb-Ta-O alloy was subjected to heat treatment to investigate its phase stability upon aging. The resultant effect on the mechanical and functional properties was systematically evaluated. The aging of the β-only microstructure, obtained by solutionizing and quenching, resulted in the formation of ultrafine α-precipitates with increasing order of size as the aging temperature increased from 400 °C to 600 °C. The variation in the size of α-precipitates effected the mechanical properties at the three different aging temperature. The highest hardening observed at 400 °C was associated with macroscopic embrittlement, whereas age softening was observed in samples aged at 600 °C due to coarsening of precipitates and softening of the β-matrix. In contrast, aging at 500 °C resulted in about 32% increase in tensile strength from the β-solutionized condition. As the samples aged at 500 °C showed optimum combination of mechanical properties among the aged samples, these were further characterized for their electrochemical, tribological and biological responses. The fretting wear studies showed that the wear rate of the solution-treated samples increased after aging due to the higher corrosion rate leading to a higher rate of tribocorrosive dissolution and formation of a transfer layer harder than that of solution treated sample. The Ti-Nb-Ta-O alloy supported the attachment and proliferation of osteoblasts similar to that on commercially pure Ti. Taken together, this work provides new insights into the preparation of next-generation Ti alloys for biomedical applications with high strength and low modulus through microstructural control induced by heat treatment.

Corrosion of Ti[sbnd]6Al[sbnd]4V orthopaedic alloy under stress

During in vivo function, implant surfaces are exposed to a corrosive environment as well as a wide range of tensile and compressive stresses. The objective of this study was to study the corrosion behavior of the Ti6Al4V orthopaedic alloy under different levels (ranging from plastic to elastic) of tensile stress, compressive stress, and combined tensile and compressive stresses in phosphate buffered saline 1X solution. The introduction of stress was found to alter the corrosion behavior of the Ti6Al4V alloy. The corrosion behavior was slightly improved under compressive stress while specimens under tensile stress showed weaker corrosion resistance compared to the specimens under zero stress. Nonetheless, the synergistic action of the tensile and compressive stresses considerably increased the corrosion activity of the specimens, more than that when they were just under tensile stress. The worst corrosion behavior was observed for the specimens under coupled elastic stress.

The effect of the inflammatory species hypochlorous acid on the corrosion and surface damage of Ti‐6Al‐4V and CoCrMo alloys

Performance of metallic orthopedic alloys is dependent on the local biological conditions within the joint. Inflammation within a joint can lead to severe conditions at the surface of the implant and may represent a driving force of corrosion which is not well understood. In this study, the corrosion response of CoCrMo and Ti-6Al-4V alloys was studied in hypochlorous acid (HOCl) saline solutions, which served as a simulated inflammatory environment. Anodic polarization and electrochemical impedance spectroscopy were used to evaluate the electrochemical behavior of these alloys in a range of hypochlorous acid solutions. The open circuit potential of CoCrMo rose to over 600 mV (vs. Ag/AgCl) in 30 mM HOCl solutions while the corresponding corrosion current increased three orders of magnitude over controls. Visual analysis of CoCrMo disks after immersion in 50 mM HOCl for 5 days revealed extensive surface damage. This study shows that HOCl can polarize CoCrMo surfaces above the transpassive potential without an external power source. Ultimately, long-term exposure to HOCl within an inflamed joint may significantly affect patient outcomes through accelerated generation of corrosion products. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3185-3194, 2018.

Qualitative and Quantitative Chemical Investigation of Orthopedic Alloys by Combining Wet Digestion, Spectroanalytical Methods and Direct Solid Analysis

In this study, two laser-based techniques, laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were used for analytical signal evaluation of Ti, Al, and V and investigation of possible harmful elements eventually present as minor elements in Ti alloys. Due to the lack of certified reference materials, samples were also analyzed by wavelength dispersive X-ray fluorescence (WDXRF) and inductively coupled plasma optical emission spectrometry (ICP OES) after microwave-assisted digestion. To maximize the efficiency of LIBS and LA-ICP-MS, operational conditions were adjusted aiming to find optimal analytical performance. LIBS showed several Ti emission lines and few signals for Al and V. LA-ICP-MS was able to detect all three major constituents. For quantitative analysis, the correlation of intensity signals from LIBS analysis with reference values obtained by ICP OES was not successful, showing that there are still difficulties for quantification using solid samples. Measurements using ICP OES showed that additionally to major constituents, only Fe was present in concentrations around 0.2%. Analysis by WDXRF confirmed the presence of Fe. Results using both methods, i.e., ICP OES and WDXRF, were in good agreement.

Hyaluronic Acid as a Matrix for Increased Functionality of Biomedical Alloys

Despite extensive knowledge on the various methods for surface modification and interface formation, many questions still remain unresolved, especially regarding the relationships between composition of the bio-environment and biomechanical, structural and chemical properties of metal surface. In vitro corrosion studies were mostly carried out is simple solutions of inorganic salts, which can be regarded only as first tests of in vivo behavior of a metal, but not sufficient for deeper understanding of in vivo behavior (1-3). Some studies were performed in biologically more relevant media like MEM and serum; some investigated the effect of addition of protein or amino acids to solution of inorganic salts (2). Hyaluronic acid (HA) is a component of synovial joint fluid that regulates many important physiological and pathophysiological reactions. It is a glycosaminoglycan (GAG) or mucopolysaccharide, a long, unbranched polysaccharide composed of repeating units of disaccharide N-acetyl-D-glucosamine and D-glucuronic acid ‒ the only non-sulfated GAG and a high molecular mass polymer in excess of 106Da. It affects cell proliferation and migration and is responsible for the viscosity and resistance to compressive stress of synovial fluid. The behaviour of orthopaedic alloys in its presence is scarcely known and needs to be assessed.It was recently reported (4) that the addition of HA significantly affect the behavior of CoCrMo alloy, especially in simulated Hanks’ physiological solution containing inorganic salts. It results in the formation of a thick layer of calcium phosphate, which is approximately ten times thicker than that in the absence of hyaluronic acid. This layer is homogeneous at the nano-level. Due to its formation, the underlying layer of chromium oxide cannot be detected. The presence of Ca2+ and PO4 3 -ions is essential for the interaction between the chromium oxide surface and the hyaluronic chain. Under the experimental conditions used the addition of hyaluronic acid does not statistically significantly affect the viability of osteoblast-like cells but does increase the activity of alkaline phosphatase, indicating its beneficial effect on osteogenic activity.In addition to osseointegration ability, another important functional property of biomedical, especially orthopaedic alloy, is its ability to resist infection. The antimicrobial effect of silver salts has been well known; recently the use of silver nanoparticles as effective microbial growth inhibitor has been reported and recognized for possible applications for diverse medical devices (5). The combination of HA and silver nanoparticles will be presented as a way of increasing functional performance of orthopaedic alloy. Method of preparation includes green synthesis of silver nanoparticles where HA plays a role of reducing and stabilizing agent (6). Synthesized complex was characterized using several experimental methods (UV/Vis, FTIR, XPS, SEM, TEM). When deposited onto metal plates, its antimicrobial activity was assessed for resistance to attachment of common bacterial strains.

Growth and electrochemical stability of self-organized TiO2nanotubes on Ti-2 grade and orthopedic Ti6Al4V alloy for biomedical application

Titanium and its alloys are biomaterials used in endosseous implants, due to desirable mechanical properties, high corrosion resistance and biocompatibility. Using electrochemical anodization technique these materials can be recovered with self-organized TiO2 nanotubes layer resulting in increased specific surface area and probable bioactivity improvement. This research aimed determine potentiostatic anodization parameters to obtain self-organized TiO2nanotubes layer with reproducibility and ideal diameters for probable bioactive response on Ti - 2 grade (ASTM F67) and Ti6Al4V (ASTM F136) orthopedic alloy and evaluation the electrochemical stability behavior in simulated body fluid media. The self-organized nanotubes layer were obtained by potentiostatic electrochemical method in electrolyte containing fluoride ions, H3PO4/HF for Ti 2 grade and H3PO4/NH4F for Ti6Al4V alloy, the applied potentials were 15 V, 20 V and 25 V for 30, 60 and 90 minutes, for both materials. For morphologic characterization were employed scanning electron microscopy SEM and the Image J software for nanodiameter measurements. The nanoestructure electrochemical stability was evaluated by open circuit potential after immersion for 15, 30 and 60 days in artificial blood plasma, into an electrochemical cell, using SCE (saturated calomel electrode) as reference electrode, in PBS ((phosphate buffered saline) solution electrolyte for 90 minutes. The ideal anodization parameters were 15 V and 20 V for 1 hour and a reproducible, uniform and homogeneous self-organized nanotubes layer were obtained with ideal diameters that probably improve the implant superficial bioactivity with 80 and 120 nm respectively, according to the literature. Open-circuit potentials from metal/oxide system obtained on both materials are stable with potentials in range of -0.031 V to -0,183 V indicating good stability of nanoestructures in simulated body fluid. Nanotubes layer as a superficial treatment is viable with high reproducibility, low cost and electrochemical stability in simulated body fluid media.

A Comparative Analysis of New Ti-Nb-Zr-Ta Orthopedic Alloys

Ti-Nb-Zr-Ta alloys represent a new generation of biomaterials with possible applications in the orthopedic field, being developed in order to eliminate the negative aspects of the current orthopedic biomaterials, which consist mainly in a low biocompatibility with human tissues and high values of modulus of elasticity compared to the human bone. This paper presents a comparative study of new titanium alloys, corresponding to the Ti-Nb-Zr-Ta system: Ti-21Nb-6Zr-15Ta and Ti-25Nb-10Zr-8Ta, which were analyzed by scanning electron microscopy, X-ray diffraction and microindentation. The both alloys are classified as near-β alloys. The addition of alloying elements such as Ta, Nb and Zr represents a good solution for lowering modulus of elasticity, which is an important factor for reducing bone resorption and therefore for preventing implant failure.

Hyaluronic acid stimulates the formation of calcium phosphate on CoCrMo alloy in simulated physiological solution

The behaviour of CoCrMo alloy has been studied in two simulated physiological solutions-NaCl and Hanks' solutions-each containing the sodium salt of hyaluronic acid. Hyaluronic acid is a component of synovial joint fluid, so the behaviour of orthopaedic alloys in its presence needs to be assessed. Electrochemical methods, X-ray photoelectron spectroscopy and scanning electron microscopy have been used to analyse the composition, thickness and morphology of any layers formed on the alloy. The addition of hyaluronic acid shifts the corrosion potential and increases the value of polarization resistance. The presence of hyaluronic acid in simulated Hanks' physiological solution stimulates the formation of a calcium phosphate layer, opening up the possibility for tailoring the surface properties of CoCrMo alloy. The viability of human osteoblast-like was determined using the Alamar(®) Blue Assay, while the osteogenic activity was evaluated by alkaline phosphatase activity. The presence of hyaluronic acid affects the alkaline phosphatase activity.

The effect of biomolecules on the behaviour of CoCrMo alloy in various simulated physiological solutions

CoCrMo orthopaedic alloy was oxidized potentiostatically in various simulated physiological solutions in order to reveal differences in the composition, thickness and structure of the surface layers formed as a function of solution composition. X-ray photoelectron spectroscopy, combined with angle-resolved measurements and depth profiling, was used for the purpose. The following simulated physiological solutions were used: (1) 0.9% NaCl, (2) simulated Hanks physiological solution containing various inorganic salts, (3) simulated Hanks physiological solution containing an aliquot of synovial fluid retrieved at a primary operation, and (4) minimum essential medium containing various inorganic salts, amino acids and vitamins. No significant differences between alloy treated in these solutions were observed after oxidation in the passive region; the oxide films are a few nanometres thick and, except in NaCl solution, contain a small amount of calcium phosphate. After oxidation at a potential in the transpassive range, however, the oxide thickness increases considerably due to incorporation of cobalt and molybdenum oxides. Further, the concentration of calcium phosphate increases. The layers formed in minimum essential medium and Hanks solution containing synovial fluid comprise nitrogen and carbon containing species. The addition of synovial fluid significantly affects the behaviour in Hanks solution.

Tribochemical Component of Oxidative Stress Development at Artificial Joints Implantation. Part 3. Inhibition of Radical-Forming and Antiproliferative Ability of Wear Particles by Antioxidants and Bone Fat

Tsepalov Inhibition ability of certain antioxidants and bone fat upon the oxidative properties of wear particles was studied. It was shown that at presence of wear particles use of BHT and б -tocoferol resulted in an inhibition of cumene oxidation. Treatment of orthopaedic alloys particles with bone fat was also accompanied by complete inhibition of oxidation reaction and duration of effect depended on the content of bone fat antioxidants. Addition of bone fat into mixture of alloy and polyethylene particles prevented the development of free-radical reactions ana potential oxidative destruction ofpolymer. Treatment of alloy particles with bone fat considerably reduced their negative influence upon human bone marrow osteogenic cells.

A novel route for processing Co-Cr-Mo orthopaedic alloys

Millions of people suffer from bone and joint inflammatory problems and usually result in extreme cases with total joint replacement. Most commonly affected joints are the hip and the knee. Over the past 20 years there has been a revival in interest of metal-on-metal hip replacements. Various alloys have been used in joint replacement, the most successful in the Cobalt-based alloys. As compared to others the cobalt based alloys have higher wear resistance and therefore less risk of failure. The most common Co-based alloy used in clinical application is the ASTM F75 alloy, which is extensively used in femoral and acetabular components. Conventional methods to fabricate the alloy are via cast or wrought techniques. Wrought alloys are better than their cast materials due to their superior mechanical properties as the forging process promotes plastic deformation. An alternative method of fabrication is via powder processing and has shown significant improvements to produce finer grained materials, which relate to enhancement in properties, such as strength, toughness, ductility. One of the key stages of powder processing is sintering of the powder to fuse the particles together. A superior but simple sintering processing is spark plasma sintering (SPS), which produces highly dense materials with minimum grain growth. This is achieved by a pulsed electrical current heating the material while applying a pressure to compact the powdered material. This process has the ability to densify nanopowders, in order to produce microstructures with finer grains and superior mechanical properties. Using SPS and nanopowders for the first time, we have been able to prepare the ASTM F75 cobalt–chromium–molybdenum (Co–Cr–Mo) orthopaedic alloy composition. In this work we have investigated, the effect of processing variables on the structural features of the alloy (phases present, grain size and microstructure). We have been able to produce specimens of >99% of the theoretical density. The structures were free of carbides, which a vital breakthrough. Detrimental carbide phases in the microstructure as found in the more conventional methods of fabrication have shown to cause problems in wear. The compacts are of higher hardness than cast or wrought products despite the absence of carbides in the microstructure. The gain in hardness is because of the presence of oxides in the microstructure and we hope to quantify the oxide content in the future. The mechanisms of oxide formation are explained by considering chemical thermodynamics and kinetics. The next step is to evaluate the tribological performance (wear, friction, lubrication regimes) of this SPS-processed material and compare its performance with conventional MoM products (cast and wrought). The SPS route offers significant advantages over the conventional cast and wrought routes used to prepare this alloy for orthopaedic applications.

Cobalt-based orthopaedic alloys: Relationship between forming route, microstructure and tribological performance

The average longevity of hip replacement devices is approximately 10–15years, which generally depends on many factors. But for younger generation patients this would mean that revisions may be required at some stage in order to maintain functional activity. Therefore, research is required to increase the longevity to around 25–30years; a target that was initially set by John Charnley. The main issues related to metal-on-metal (MoM) hip replacement devices are the high wear rates when malpositioned and the release of metallic ions into the blood stream and surrounding tissues. Work is required to reduce the wear rates and limit the amount of metallic ions being leached out of the current MoM materials, to be able to produce an ideal hip replacement material. The most commonly used MoM material is the cobalt-based alloys, more specifically ASTM F75, due to their excellent wear and corrosion resistance. They are either fabricated using the cast or wrought method, however powder processing of these alloys has been shown to improve the properties. One powder processing technique used is spark plasma sintering, which utilises electric current Joule heating to produce high heating rates to sinter powders to form an alloy. Two conventionally manufactured alloys (ASTM F75 and ASTM F1537) and a spark plasma sintered (SPS) alloy were evaluated for their microstructure, hardness, tribological performance and the release of metallic content. The SPS alloy with oxides and not carbides in its microstructure had the higher hardness, which resulted in the lowest wear and friction coefficient, with lower amounts of chromium and molybdenum detected from the wear debris compared to the ASTM F75 and ASTM F1537. In addition the wear debris size and size distribution of the SPS alloy generated were considerably small, indicating a material that exhibits excellent performance and more favourable compared to the current conventional cobalt based alloys used in orthopaedics.