CoCrMo Implants Research Articles

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.

Detailed insight into chromium species released from failed CoCrMo implants: Ex vivo periprosthetic tissues study.

This unique study provides information on Cr species and their distribution in periprosthetic tissues of patients with metal-on-polyethylene joint implants. Co-Cr-Mo alloy has been widely used in joint replacement and represents a source of metal derived species. In the case of chromium, previous studies on periprosthetic tissues revealed mainly Cr(III) distribution, whereas the potential release of carcinogenic Cr(VI) species has been still a subject of debate. Here, an analytical approach utilizing speciation and fractionation was developed to analyze periprosthetic tissue samples collected from wide range of patients with failed total hip or knee replacements. The results reveal that Cr(III) is mainly released in the form of insoluble CrPO4 and Cr2 O3 particles. The highest Cr contents were found in periprosthetic tissues of patients suffering from aseptic loosening and having more Cr-based implants in the body. Cr species penetrated tissue layers, but their levels decreased with the distance from an implant. The detailed speciation/fractionation study carried out using the set of consecutive periprosthetic tissues of a patient with extensive metallosis showed the presence of trace amounts of free Cr(III), nanoparticles, and metal-protein complexes, but the majority of Cr still occurred in CrPO4 form. Carcinogenic Cr(VI) species were not detected. Up to date, there is no published human tissue study focused on the detailed speciation of both soluble and insoluble Cr-based species in the context of failing total hip and knee replacements.

The influence of cathodic potentials on the surface oxide layer status and tribocorrosion behaviour of Ti6Al4V and CoCrMo alloys in simulated body fluid

Ti6Al4V and CoCrMo alloys are important metallic materials in orthopaedics applications because of their excellent combination of corrosion resistance, mechanical properties, and biocompatibility. However, Ti6Al4V possesses poor wear resistance, and CoCrMo implants have been reported to release toxic ions in vivo. In addition, orthopaedics applications are subjected to corrosive media and cyclic stresses, increasing the likelihood of scratching the surface, removing the protective oxide film, and thereby causing cathodic polarisation of the system. The present work examined the material loss in tribocorrosion and the thickness and resistivity (status) of the oxide layer under different cathodic potentials. The cathodic polarisation conditions were chosen to reflect those that might be found in vivo. The results explicitly showed a different impact of the cathodic potentials on the tribocorrosion behaviour of the two materials.

Electronic properties and surface potential evaluations at the protein nano-biofilm/oxide interface: Impact on corrosion and biodegradation

The formation of a protein nano-biofilm, which exhibits a special electronic behavior, on the surface of metals or oxide biomaterials considerably influences the crucial subsequent interactions, particularly the corrosion and biodegradation processes. This study discusses the impact of electrical surface potential (ESP) of a single or nano-biofilm of albumin protein on the electrochemical interactions and electronic property evolutions (e.g., charge carriers, space charge capacitance (SCC), and band bending) occurring on the surface oxide of CoCrMo implants. Scanning Kelvin probe force microscopy (SKPFM) results indicated that ESP or surface charge distribution on a single or nano-biofilm of the albumin protein is lower than that of a CoCrMo complex oxide layer, which hinders the charge transfer at the protein/electrolyte interface. Using a complementary approach, which involved performing Mott-Schottky analysis at the electrolyte/protein/oxide interface, it was revealed that the albumin protein significantly increases the SCC magnitude and number of n-type charge carrier owing to increased band bending at the SCC/protein interface; this facilitated the acceleration of metal ion release and metal-protein complex formation. The nanoscale SKPFM and electrochemical analyses performed in this study provide a better understanding of the role of protein molecules in corrosion/biodegradation of metallic biomaterials at the protein nano-biofilm/oxide interface.

"Systematic review and meta-analysis of ceramic coated implants in total knee arthroplasty. Comparable mid-term results to uncoated implants."

Nitride-based ceramic coatings, such as titanium nitride (TiN) and titanium niobium nitride (TiNbN), have been introduced in total knee arthroplasty (TKA) to enhance the mechanical properties and biocompatibility of knee components, harden the metal surface and reduce CoCrMo exposure and metal ion release. However, the theoretical advantages of these ceramic coatings in TKA have yet to be fully elucidated. This systematic review aimed to provide clinical evidence on mid-term outcomes of ceramic-coated knee prostheses in comparison with uncoated standard CoCrMo knee prostheses in primary TKA. The hypothesis was that ceramic-coated implants can be used in primary TKA with no inferior outcomes compared to uncoated CoCrMo implants. A systematic review of the literature was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to find all clinical studies regarding primary TKA with ceramic-coated knee prostheses. MEDLINE (PubMed), Embase and Cochrane Library were searched from 1990 to October 2020 to identify relevant studies for the first qualitative analysis. Using PICOS eligibility criteria, a subgroup of the selected studies was used to perform a meta-analysis. Fifteen studies were included in this systematic review, of which six were included in the meta-analysis: 3 randomized controlled trials, 2 retrospective comparative studies and 1 prospective cross-sectional study. Pooled data overall included 321 coated TKAs vs. 359 uncoated TKAs and a mean follow-up of 4.6years (range, 2-10years). No significant difference in the implant survival risk ratio with revision or reoperation due to any reason was found between coated and uncoated TKAs, even considering the RCT study subgroup with a risk ratio of 1.02 (P = 0.34). No significant differences were found for postoperative complications, clinical scores, or metal blood concentrations at 1year. The findings of this systematic review and meta-analysis support the statement that ceramic-coated TKAs are not inferior to uncoated TKAs, showing comparable survival rates, complication rates and clinical outcomes. There is strong evidence that ceramic-coated TKA does not improve the clinical results or survival rate in comparison with uncoated TKA. II, Therapeutic.

Preclinical evaluation of a mini-arthroplasty implant based on polyetheretherketone and Ti6AI4V for treatment of a focal osteochondral defect in the femoral head of the hip

A mini or partial arthroplasty may offer the advantages of reduced pain, shorter hospital stay, and increased range of motion, which are beneficial for the treatment of large-sized focal osteochondral defects. We aimed to evaluate the in vivo histologic response and function of our nonresorbable, composite structure implant, developed using polyetheretherketone (PEEK) and Ti6AI4V alloy, as a treatment for full-thickness osteochondral defects in the femoral head of the hip using a goat model. The gross and imaging appearance and histologic results were compared to those of a similar size cobalt-chromium-molybdenum (CoCrMo) alloy implant placed in a defect in the femoral head and evaluated up to 12 weeks. The X radiographs showed that there was no evidence of loosening of the implants for both the PEEK-Ti6AI4V and CoCrMo groups. Magnetic resonance imaging results showed no inflammatory signal findings in both PEEK-Ti6AI4V and CoCrMo implants. Macroscopically and histologically, there was lesser cartilage degeneration in the PEEK-Ti6AI4V implant than in the CoCrMo implant. The modified macroscopic articular evaluation score was lower in the PEEK-Ti6AI4V group than in the CoCrMo group (p < 0.05), and the histological score of the periprosthetic and acetabular cartilage was lower in the PEEK-Ti6AI4V group than in the CoCrMo group (P < 0.05). The micro-computed tomography results showed that the uncemented PEEK-Ti6AI4V implant has better osseointegration and higher bone-implant contact than the cemented CoCrMo implant. The peri-implant bone mass was higher in the PEEK-Ti6AI4V implant(p < 0.05). Meanwhile, the optical profile analytical results showed that the surface roughness of the cartilage in the acetabulum was higher in the CoCrMo group. In conclusion, the mini-arthroplasty implant based on PEEK-Ti6AI4V was superior to an identical CoCrMo alloy implant as a treatment for local osteochondral defect in the femoral head, owing to its in vivo cartilage protection and better osseointegration.

The effect of hyaluronic acid on the corrosion of an orthopedic CoCrMo-alloy in simulated inflammatory conditions

During joint inflammation, various reactive oxygen species (ROS) are present in the surrounding tissue and joint fluid. In the laboratory, hydrogen peroxide (H2O2) is typically used to simulate inflammatory conditions, and media containing proteins and hyaluronic acid (HA) are employed to simulate joint synovial fluid. Electrochemical interactions between H2O2 and HA in the presence of a CoCrMo surface are expected, since HA molecules contain redox-active moieties. We hypothesized that any redox reactions of these moieties with ROS will mitigate the oxidizing effect of H2O2 on the CoCrMo surface, limiting the corrosion rate of the metal.Non-destructive electrochemical measurements (open circuit potential, linear polarization resistance and electrochemical impedance spectroscopy) were used to investigate the corrosion response of CoCrMo in synovial model fluid containing physiologically relevant concentrations of albumin proteins and hyaluronic acid, with and without H2O2. Two different molarities of H2O2, 3 mM and 30 mM, were tested. While both molarities are within physiological limits, 3 mM is well within the range HA could mitigate, whereas 30 mM is not.Contrary to our hypothesis, HA did not alleviate corrosion in 3 mM H2O2 and even caused a corrosion increase in the case of 30 mM H2O2. The decrease in corrosion resistance of the alloy may be attributed to the complexation of degenerated HA molecular chains with chromium ions released from the metallic surface, which are necessary to build a protective oxide film. This finding has clinical implications, suggesting that HA accelerates corrosion of CoCrMo implants in the presence of strong inflammation.

Improved Tribocorrosion Resistance of a CoCrMo Implant Material by Carburising

Tribocorrosion damage is a cause for the premature failure of hip implants made of cobalt-based alloys. Low-temperature carburising can be a plausible solution towards mitigating the tribocorrosion damage of articulating components. This diffusion treatment introduces a supersaturated carbon solid solution, termed S-phase, which hardens the CoCrMo alloy without detriment to the corrosion resistance. This work investigates and compares the tribocorrosion behaviour of untreated and carburised ASTM F1537 CoCrMo alloys tested in Ringer’s solution using a reciprocating sliding configuration against a polycrystalline alumina counterface under different electrochemical conditions. The research shows that whereas the carburised alloy suffered a slightly higher wear loss under a cathodic potential, it was able to reduce the material losses considerably when tested under both open circuit and anodic potential conditions. Under anodic conditions material losses by corrosion due to wear dominated. The better tribocorrosion resistance of the carburised layer was attributed to the better qualities of the passive film for the carburised sample coupled with an increased load support.

Effect of Temperature, Electrolyte Composition and Immersion Time on the Electrochemical Corrosion Behavior of CoCrMo Implant Alloy Exposed to Physiological Serum and Hank's Solution

A new study about corrosion behavior of CoCrMo alloy used as implant material exposed to the physiological serum and Hank's solution in different temperatures, electrolyte compositions and immersion time were simulated, using open circuit potential (OCP), potentiodynamic polarization curves (PPC) and electrochemical impedance spectroscopy (EIS.) From the results, it can be concluded that CoCrMo biomaterial is influenced by electrolyte composition and temperature, and the passive films were more protective when formed in presence of physiological serum. Comparing the Ecorr for both solutions, it is possible to verify that the Hank's solution presented values more negative for the two studied temperatures (25 and 37 °C), indicating a greater susceptibility to the corrosion process. Regarding the results of potentiodynamic polarization, the ipass, decreased as function of time, indicating a more protective passive film at 25 °C. In regards to the physiological serum, the highest ipass values at 37 oC evidenced the formation of a less stable passive film. The different behavior of ipass in Hank's solution may be related to the competitiveness between a possible film of D-glucose and oxides of the alloy metals. EIS studies suggest that the film formed in presence of physiological serum is nobler than that with Hank's solution.

In vivo corrosion of CoCrMo alloy and biological responses: a review

In vivo corrosion of cobalt-chromium-molybdenum (CoCrMo) alloy and its potential adverse effects on the body have been recognized as a major concern for its use as biomaterials in recent years. While the underlying mechanism of general and mechanically-assisted corrosion (MAC) related to orthopedic implants have been well-documented and extensive research have been focused on how metal ions and wear particles affect biological response, recent reports of inflammatory cell-induced corrosion (ICIC) on CoCrMo implants have challenged traditional one-way arrow understanding of the relationship between biological system and corrosion, which is ‘corrosion causes biological responses’, proposing a new concept: biology induces corrosion. This article provides a brief overview on in vivo corrosion of CoCrMo hip implants while focusing on ICIC and new perspective of the two-way feedback loop between corrosion and human body. Recent retrieval studies on ICIC and its clinical relevance will be presented. Biological elements, reactive chemical species and electrochemistry related to the underlying mechanism of ICIC will be discussed.

Evidence for the dissolution of molybdenum during tribocorrosion of CoCrMo hip implants in the presence of serum protein

We have developed an important new protocol for the analysis of metal ion levels in fluids extracted from hip implant patients and also hip simulators. Using this procedure, we present a new perspective on the release of metal ions from CoCrMo alloy implants, revealing significantly lower levels of metal ion release during tribocorrosion in hip simulators than previously thought, combined with the release of much higher percentages of molybdenum ions relative to cobalt and chromium. This work is of relevance, both from the perspective of the fundamental science and study of metal-protein interactions, enabling understanding of the ongoing problem associated with the biotribocorrosion and the link to inflammation associated with Metal-on-Metal (MoM) hip implants made from CoCrMo alloys.

Optimization of electrochemical step deposition for bioceramic hydroxyapatite coatings on CoCrMo implants

Abstract CoCrMo metallic implants were coated with a bioceramic hydroxyapatite layer using a modified step electro-deposition at room temperature. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to model and optimize the step deposition parameters, such as initial potential, scan rate and peak potential. Interactions between step deposition parameters and in vitro corrosion performance of the coatings were modeled by response surface plots. Predicted and experimental values were fitted with high accuracy. The effects of the step deposition parameters were evaluated within the limits of lowest applied potential (− 0.03 to − 1.17 V), scan rate (3.43–116.57 mV/s) and highest applied deposition potential (− 1.08 to − 1.92 V). A 5-level-3-factor experiment plan was used to optimize step deposition parameters. Optimum conditions for the modified step deposition parameters were determined as initial potential of − 0.76 V, peak potential of − 1.67 V and scan rate of 59.33 mV/s.

Acid Etching does not Improve CoCrMo Implant Osseointegration in a Canine Implant Model

Induction of bone ingrowth by topographical changes to implant surfaces is an attractive concept. Topographical modifications achieved by acid etching are potentially applicable to complex 3D surfaces. Using clinically relevant implant models, we explored the effect of wet etching porous bead-coated CoCrMo. The study was designed as two paired animal experiments with 10 dogs. Each dog received four implants; one in each medial femoral condyle (loaded 0.75-mm-gap model) and one in each proximal tibia (press-fit). The implants were observed for 6 weeks and were evaluated by biomechanical pushout tests and histomorphometry. We found that wet etching porous bead-coated CoCrMo implants failed to improve implant performance. Moreover, a tendency towards increased fibrous tissue formation, decreased new bone formation, and decreased mechanical fixation was observed. Surface topography on implants is able to stimulate bone-forming cells, but the clinical performance of an implant surface perhaps relies more on 3D geometrical structure and biocompatibility. Caution should be exercised regarding the results of wet etching of porous bead-coated CoCrMo and there is a need for more preclinical trials.

Biomechanical implant fixation of CoCrMo coating inferior to titanium coating in a canine implant model

The use of CoCrMo in orthopedic surgery is not new, and CoCrMo (cobalt-chromium-molybdenum) is well tolerated. Nevertheless, the alloy is still considered less biocompatible than titanium. We therefore wanted to explore the biocompatibility of CoCrMo by investigating the biomechanical implant fixation and implant osseointegration of CoCrMo (ASTM F-75) porous bead-coated and titanium (ASTM F-136) porous bead-coated implants. In 10 dogs, the two implant types were inserted into the proximal part of the humerus. Implant sites were overdrilled, leaving an empty 0.75-mm gap between implant and surrounding bone. The implants were observed for 6 weeks and were evaluated by biomechanical push-out test and histomorphometry. We found a statistically significant 40% decrease in the biomechanical fixation of CoCrMo porous bead-coated implants compared with titanium porous bead-coated implants. Implant osseointegration was comparable between the two implants; however, a slight decrease in bone volume density around CoCrMo implants was observed. Insertions of CoCrMo implants are associated with a disturbance of the delicate peri-implant milieu. Even from implants not subjected to any mechanical forces, metal ions are liberated and result in intra- and extracellular accumulation in the immediate implant vicinity, presenting a likely explanation for our findings. A 40% reduction of initial implant fixation could prove to be serious because initial implant fixation is critical for long-term performance. The choice between titanium alloy and CoCrMo should, however, ultimately be governed by a comprehensive review of all factors influencing clinical implant survival. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Microstructure and wear properties of LENS® deposited medical grade CoCrMo

There is a growing interest in metal-on-metal bearing surfaces for orthopedic implants. Although some success has been achieved in applications like hip implants which involve a large contact area, non-conforming joints, such as knees, have proved more difficult. The current work examines the applicability of a novel additive manufacturing process, Laser Engineered Net Shaping (LENS), the registered trademark and service mark of Sandia National Laboratories and Sandia Corporation), for producing CoCrMo implants. A series of experiments were conducted to determine the optimum parameters for deposition of CoCrMo. Microstructural studies, hardness tests, and dry sand/rubber wheel abrasive wear tests were conducted on the LENS deposits. The results showed that metallurgically sound deposits can be produced using the LENS process under optimized conditions. The hardness of the LENS deposited CoCrMo was found to be comparable to that of standard CoCrMo wrought material; however, wear tests indicated that LENS deposits were considerably less resistant to abrasive wear than wrought CoCrMo. The reasons for this behaviour are discussed based on microstructural observations.

Behaviour of a CoCrMo Implant Alloys in Ringer????s Type Solutions Studied by Electrochemical and Surface Analysis Techniques

Behaviour of a CoCrMo Implant Alloys in Ringer????s Type Solutions Studied by Electrochemical and Surface Analysis Techniques

Electrochemical corrosion and metal ion release from Co-Cr-Mo prosthesis with titanium plasma spray coating

The corrosion behavior of CoCrMo implants with rough titanium coatings, applied by different suppliers by either sintering or vacuum plasma spraying, has been evaluated and compared with uncoated material. The open-circuit potential, corrosion current and polarization resistance were determined by electrochemical techniques. The Co, Cr and Ti ions released from the samples into the electrolyte during a potentiostatic extraction technique were analyzed using ICP-MS. The Ti coatings from the different suppliers showed a different porous morphology, and the implants exhibited a distinct corrosion activity, underlining the importance of the coating process parameters. Among the titanium coated samples, the one with the sintered overcoat turned out to be the most resistant. Yet, on an absolute scale, they all showed a corrosion resistance inferior to that of uncoated CoCrMo or wrought titanium.

Deposition of highly adhesive ZrO 2 coating on Ti and CoCrMo implant materials using plasma spraying

ZrO 2 (4%CeO 2) and ZrO 2 (3%Y 2O 3) coatings were deposited on titanium (Ti) and CoCrMo implants using plasma spraying and the adhesive, morphological and structural properties of the plasma-sprayed coatings were evaluated. Characterization of these coatings was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness, hardness, and adhesive strength. XRD patterns showed that both the coatings appeared to be primitive tetragonal phase. SEM observations showed that both the ZrO 2 coatings appeared to be rough, porous and melted. The cross-section surface morphology of the coatings, coating–substrate interfaces and substrates without acid etching was very dense and smooth. After acid etching, as compared to the dense ZrO 2 coating–CoCrMo substrate interfaces, the thin gaps appeared within the ZrO 2 coating–Ti substrate interfaces. It is suggested that plasma spraying probably formed an amorphous Ti layer in the coating–Ti substrate interface that can be removed by acid etching. The average surface roughness of ZrO 2 (3%Y 2O 3) and ZrO 2 (4%CeO 2) coatings was correlated to the starting powder size and substrates. No significant difference between the hardness of all coatings and substrates was observed. The adhesive strengths of ZrO 2 (4%CeO 2) coating to Ti and CoCrMo substrates were higher than 68 MPa and significantly greater than that of ZrO 2 (3%Y 2O 3) coatings.

Carcinogenicity of CoCrMo (F-75) implants in the rat.

A long-term study was conducted in rats to assess the contribution of the surface area of CoCrMo devices to carcinogenesis. Groups consisting of 104 rats each (52 male, 52 female) were either implanted with metal cylinders fixed on the left, lateral femur (groups 1-3) or injected with a suspension of metal microspheres in the dorsal subcutis (group 4). Group 1 (control) received solid Ti6Al4V cylinders [surface area to body weight (SA/BW) ratio measuring 1.35 times that of human total hip prosthesis (HTHP)]. Group 2 was implanted with solid CoCrMo (SA/BW ratio: identical to implants of group 1). Group 3 received sintered-porous CoCrMo devices (SA/BW ratio: 30 x HTHP). Group 4 was injected with a suspension of CoCrMO microspheres (SA/BW ratio: 135 x HTHP). Implant-associated tumors (IATs) were observed in 23, 14, 3, and 15 rats of groups 1, 2, 3, and 4, respectively. Within groups 1 and 2, 34 IATs were associated with loose implants, three with undetermined implant fixation status, and none with fixed implants. A significantly increased accumulation of chronic inflammatory tissues around loose rather than fixed implants suggested a foreign-body reaction as the primary mechanism of carcinogenesis. A secondary role in carcinogenesis was ascribed to the increased CoCrMo implant SA/BW ratios as indicated by a 14.6% IAT incidence in group 4 versus 3% in group 3. These results support the notion that early intervention in the removal of loose metal devices is warranted to mitigate against foreign body-induced carcinogenesis, at least in this animal model.