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Lee H, Kurtz MA, Gilbert JL. Reactive oxygen species, electrode potential and pH affect CoCrMo alloy corrosion and semiconducting behavior in simulated inflammatory environments. Acta Biomater 2024; 186:507-519. [PMID: 39147253 DOI: 10.1016/j.actbio.2024.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 07/18/2024] [Accepted: 08/06/2024] [Indexed: 08/17/2024]
Abstract
Crevice corrosion in modular taper junctions of hip or knee replacements using cobalt-chrome-molybdenum (CoCrMo) alloys remains a clinical concern. Non-mechanically-driven corrosion has been less explored compared to mechanically assisted crevice corrosion. This study hypothesized that solution chemistry within crevices, inflammation, and cathodic electrode potential shifts during fretting result in low pH and generate reactive oxygen species (ROS), affecting oxide film behavior. This study investigated how resistance and capacitance of the CoCrMo oxide film (i.e., corrosion resistance) are modified in simulated in vivo crevice environments of modular taper junctions. Six solutions were evaluated (two pH levels: 1 and 7.4 and four hydrogen peroxide (H2O2) concentrations: 0, 0.001, 0.01 and 0.1 M). Rp versus voltage and Mott-Schottky plots were created from symmetry-based electrochemical impedance spectroscopy (sbEIS). At pH 1, the semiconductor transition to p-type occurs at more anodic potentials and higher flat band potentials were found. H2O2 decreased the flat band potential and slope in the Mott-Schottky plot. Higher H2O2 in pH 7.4 solution significantly modified the oxide film, leading to increased donor density (p = 0.0004) and a 150-fold reduction in Rp in the cathodic potential range at -1 V (p = 0.0005). The most unfavorable condition (0.1 M H2O2 pH 1) resulted in a 250-fold lower resistance compared to phosphate buffered saline (PBS) pH 7.4 at -1 V (p = 0.0013). This study highlights the corrosion susceptibility of CoCrMo under adverse chemical and potential conditions, identifying increased defects in the oxide film due to ROS, hydrogen ions and electrode potential. STATEMENT OF SIGNIFICANCE: Corrosion of cobalt chrome molybdenum alloy caused by direct chemical attack in the crevice region of hip replacements, such as modular taper junctions, remains a clinical concern. The junction environment contains adverse chemical compositions, including high acidity and reactive oxygen species (ROS) due to inflammatory responses against the corrosion products. We simulate inflammatory environments with different pH levels and hydrogen peroxide, representative of ROS. We employ electrochemical impedance spectroscopy and apply stepwise voltage over the range induced by tribocorrosion processes. We relate the effect of adverse chemical components on corrosion and semiconducting behavior of the oxide film using Mott-Schottky analysis. This study shows how pH and ROS concentration compromises the oxide film potentially leading to non-mechanically induced corrosion.
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Affiliation(s)
- Hwaran Lee
- Clemson - Medical University of South Carolina Bioengineering Program, Department of Bioengineering, Clemson University, Bioengineering Building, 101D, MSC 501, 68 Presidents St, BE 325, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Michael A Kurtz
- Clemson - Medical University of South Carolina Bioengineering Program, Department of Bioengineering, Clemson University, Bioengineering Building, 101D, MSC 501, 68 Presidents St, BE 325, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Jeremy L Gilbert
- Clemson - Medical University of South Carolina Bioengineering Program, Department of Bioengineering, Clemson University, Bioengineering Building, 101D, MSC 501, 68 Presidents St, BE 325, Medical University of South Carolina, Charleston, SC 29425, USA.
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2
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Tauviqirrahman M, Ammarullah MI, Jamari J, Saputra E, Winarni TI, Kurniawan FD, Shiddiq SA, van der Heide E. Analysis of contact pressure in a 3D model of dual-mobility hip joint prosthesis under a gait cycle. Sci Rep 2023; 13:3564. [PMID: 36864170 PMCID: PMC9981612 DOI: 10.1038/s41598-023-30725-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 02/28/2023] [Indexed: 03/04/2023] Open
Abstract
Hip joint prostheses are used to replace hip joint function in the human body. The latest dual-mobility hip joint prosthesis has an additional component of an outer liner that acts as a cover for the liner component. Research on the contact pressure generated on the latest model of a dual-mobility hip joint prosthesis under a gait cycle has never been done before. The model is made of ultrahigh molecular weight polyethylene (UHMWPE) on the inner liner and 316L stainless steel (SS 316L) on the outer liner and acetabular cup. Simulation modeling using the finite element method is considered static loading with an implicit solver for studying the geometric parameter design of dual-mobility hip joint prostheses. In this study, simulation modeling was carried out by applying varying inclination angles of 30°, 40°, 45°, 50°, 60°, and 70° to the acetabular cup component. Three-dimensional loads were placed on femoral head reference points with variations of femoral head diameter used at 22 mm, 28 mm, and 32 mm. The results in the inner surface of the inner liner, the outer surface of the outer liner, and the inner surface of the acetabular cup showed that the variations in inclination angle do not have a major effect on the maximum contact pressure value on the liner component, where the acetabular cup with an inclination angle of 45° can reduce contact pressure more than the other studied inclination angle variations. In addition, it was found that the 22 mm diameter of the femoral head increases the contact pressure. The use of a larger diameter femoral head with an acetabular cup configuration at a 45° inclination can minimize the risk of implant failure due to wear.
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Affiliation(s)
- Mohammad Tauviqirrahman
- Department of Mechanical Engineering, Faculty of Engineering, Diponegoro University, Semarang, 50275, Central Java, Indonesia.
| | - Muhammad Imam Ammarullah
- Department of Mechanical Engineering, Faculty of Engineering, Pasundan University, Bandung, 40153, West Java, Indonesia
- Biomechanics and Biomedics Engineering Research Centre, Pasundan University, Bandung, 40153, West Java, Indonesia
- Undip Biomechanics Engineering and Research Centre (UBM-ERC), Diponegoro University, Semarang, 50275, Central Java, Indonesia
| | - J Jamari
- Department of Mechanical Engineering, Faculty of Engineering, Diponegoro University, Semarang, 50275, Central Java, Indonesia
- Undip Biomechanics Engineering and Research Centre (UBM-ERC), Diponegoro University, Semarang, 50275, Central Java, Indonesia
| | - Eko Saputra
- Department of Mechanical Engineering, Semarang State Polytechnic, Semarang, 50275, Central Java, Indonesia
| | - Tri Indah Winarni
- Undip Biomechanics Engineering and Research Centre (UBM-ERC), Diponegoro University, Semarang, 50275, Central Java, Indonesia
- Department of Anatomy, Faculty of Medicine, Diponegoro University, Semarang, 50275, Central Java, Indonesia
- Center for Biomedical Research (CEBIOR), Faculty of Medicine, Diponegoro University, Semarang, 50275, Central Java, Indonesia
| | - Febri Dwi Kurniawan
- Department of Mechanical Engineering, Faculty of Engineering, Diponegoro University, Semarang, 50275, Central Java, Indonesia
- Undip Biomechanics Engineering and Research Centre (UBM-ERC), Diponegoro University, Semarang, 50275, Central Java, Indonesia
| | - Shidnan Amir Shiddiq
- Department of Mechanical Engineering, Faculty of Engineering, Diponegoro University, Semarang, 50275, Central Java, Indonesia
- Undip Biomechanics Engineering and Research Centre (UBM-ERC), Diponegoro University, Semarang, 50275, Central Java, Indonesia
| | - Emile van der Heide
- Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, Postbox 217, 7500 AE, Enschede, The Netherlands
- Laboratory for Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, Postbox 217, 7500 AE, Enschede, The Netherlands
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Wear debris in metal-on-metal bearings and modular junctions : What have we learned from the last decades? ORTHOPADIE (HEIDELBERG, GERMANY) 2023; 52:206-213. [PMID: 36820850 DOI: 10.1007/s00132-023-04346-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/12/2023] [Indexed: 02/24/2023]
Abstract
Metal-on-metal (MoM) bearing hip arthroplasty saw increasing utilization and peaked in the 1990s and early 2000s. Although the linear and volumetric wear rate for a MoM bearings was lower than its polyethylene counterpart, metal ion particles were found to be approximately 10 × smaller and 500 × higher in quantity compared to polyethylene wear debris. Research into these articulations have demonstrated their relationship to the formation of lymphocyte-mediated adverse local tissue reactions. The work-up for metal particle-associated conditions (metallosis) includes a thorough patient history and physical examination, blood laboratory studies for metal ion concentrations, and advanced imaging studies including magnetic resonance imaging (MRI). The treatment of metallosis and adverse local tissue reactions ranges from close serial observation to extensive debridement and full revision of arthroplasty components, when indicated.
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4
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Pechancová R, Gallo J, Baron D, Milde D, Antal P, Slobodová Z, Lemr K, Pluháček T. Detailed insight into chromium species released from failed CoCrMo implants: Ex vivo periprosthetic tissues study. J Biomed Mater Res B Appl Biomater 2023; 111:271-283. [PMID: 36507699 DOI: 10.1002/jbm.b.35149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 07/26/2022] [Accepted: 08/01/2022] [Indexed: 12/15/2022]
Abstract
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.
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Affiliation(s)
- Radka Pechancová
- Department of Analytical Chemistry, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic
| | - Jiří Gallo
- Department of Orthopedics, Faculty of Medicine and Dentistry, Palacký University Olomouc, University Hospital Olomouc, Olomouc, Czech Republic
| | - Daniel Baron
- Department of Analytical Chemistry, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic
| | - David Milde
- Department of Analytical Chemistry, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic
| | - Peter Antal
- Department of Inorganic Chemistry, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic
| | - Zuzana Slobodová
- Department of Clinical and Molecular Pathology, Faculty of Medicine and Dentistry, Palacký University Olomouc, Olomouc, Czech Republic
| | - Karel Lemr
- Department of Analytical Chemistry, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic.,Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tomáš Pluháček
- Department of Analytical Chemistry, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic
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5
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Driving electrochemical corrosion of implanted CoCrMo metal via oscillatory electric fields without mechanical wear. Sci Rep 2021; 11:22366. [PMID: 34785746 PMCID: PMC8595661 DOI: 10.1038/s41598-021-01810-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 11/02/2021] [Indexed: 11/08/2022] Open
Abstract
Decades of research have been dedicated to understanding the corrosion mechanisms of metal based implanted prosthetics utilized in modern surgical procedures. Focused primarily on mechanically driven wear, current fretting and crevice corrosion investigations have yet to precisely replicate the complex chemical composition of corrosion products recovered from patients' periprosthetic tissue. This work specifically targets the creation of corrosion products at the metal on metal junction utilized in modular hip prosthetics. Moreover, this manuscript serves as an initial investigation into the potential interaction between implanted CoCrMo metal alloy and low amplitude electrical oscillation, similar in magnitude to those which may develop from ambient electromagnetic radiation. It is believed that introduction of such an electrical oscillation may be able to initiate electrochemical reactions between the metal and surrounding fluid, forming the precursor to secondary wear particles, without mechanically eroding the metal's natural passivation layer. Here, we show that a low magnitude electrical oscillation (≤ 200 mV) in the megahertz frequency (106 Hz) range is capable of initiating corrosion on implanted CoCrMo without the addition of mechanical wear. Specifically, a 50 MHz, 200 mVpp sine wave generates corrosion products comprising of Cr, P, Ca, O, and C, which is consistent with previous literature on the analysis of failed hip prosthetics. These findings demonstrate that mechanical wear may not be required to initiate the production of chemically complex corrosion products.
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6
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Bergiers S, Hothi H, Henckel J, Di Laura A, Belzunce M, Skinner J, Hart A. The in vivo location of edge-wear in hip arthroplasties : combining pre-revision 3D CT imaging with retrieval analysis. Bone Joint Res 2021; 10:639-649. [PMID: 34605661 PMCID: PMC8559968 DOI: 10.1302/2046-3758.1010.bjr-2021-0132.r1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Aims Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning. Methods 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane. Results Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar. Conclusion The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning. Cite this article: Bone Joint Res 2021;10(10):639–649.
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Affiliation(s)
- Sean Bergiers
- Institute of Orthopaedics and Musculoskeletal Science, University College London, London, UK
| | - Harry Hothi
- Institute of Orthopaedics and Musculoskeletal Science, University College London, London, UK.,Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
| | - Johann Henckel
- Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
| | - Anna Di Laura
- Institute of Orthopaedics and Musculoskeletal Science, University College London, London, UK.,Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
| | | | - John Skinner
- Institute of Orthopaedics and Musculoskeletal Science, University College London, London, UK.,Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
| | - Alister Hart
- Institute of Orthopaedics and Musculoskeletal Science, University College London, London, UK.,Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
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7
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Perino G, De Martino I, Zhang L, Xia Z, Gallo J, Natu S, Langton D, Huber M, Rakow A, Schoon J, Gomez-Barrena E, Krenn V. The contribution of the histopathological examination to the diagnosis of adverse local tissue reactions in arthroplasty. EFORT Open Rev 2021; 6:399-419. [PMID: 34267931 PMCID: PMC8246109 DOI: 10.1302/2058-5241.6.210013] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The histopathological examination of the periprosthetic soft tissue and bone has contributed to the identification and description of the morphological features of adverse local tissue reactions (ALTR)/adverse reactions to metallic debris (ARMD). The need of a uniform vocabulary for all disciplines involved in the diagnosis and management of ALTR/ARMD and of clarification of the parameters used in the semi-quantitative scoring systems for their classification has been considered a pre-requisite for a meaningful interdisciplinary evaluation. This review of key terms used for ALTR/ARMD has resulted in the following outcomes: (a) pseudotumor is a descriptive term for ALTR/ARMD, classifiable in two main types according to its cellular composition defining its clinical course; (b) the substitution of the term metallosis with presence of metallic wear debris, since it cannot be used as a category of implant failure or histological diagnosis; (c) the term aseptic lymphocytic-dominated vasculitis- associated lesion (ALVAL) should be replaced due to the absence of a vasculitis with ALLTR/ALRMD for lymphocytic-predominant and AMLTR/AMRMD for macrophage-predominant reaction. This review of the histopathological classifications of ALTR/ARMD has resulted in the following outcomes: (a) distinction between cell death and tissue necrosis; (b) the association of corrosion metallic debris with adverse local lymphocytic reaction and tissue necrosis; (c) the importance of cell and particle debris for the viscosity and density of the lubricating synovial fluid; (d) a consensus classification of lymphocytic infiltrate in soft tissue and bone marrow; (e) evaluation of the macrophage infiltrate in soft tissues and bone marrow; (f) classification of macrophage induced osteolysis/aseptic loosening as a delayed type of ALTR/ARMD; (g) macrophage motility and migration as possible driving factor for osteolysis; (h) usefulness of the histopathological examination for the natural history of the adverse reactions, radiological correlation, post-marketing surveillance, and implant registries. The review of key terms used for the description and histopathological classification of ALTR/ARMD has resulted in a comprehensive, new standard for all disciplines involved in their diagnosis, clinical management, and long-term clinical follow-up.
Cite this article: EFORT Open Rev 2021;6:399-419. DOI: 10.1302/2058-5241.6.210013
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Affiliation(s)
- Giorgio Perino
- Department of Orthopedics and Orthopedic Surgery, University Medicine Greifswald, Greifswald, Germany
| | - Ivan De Martino
- Division of Orthopaedics and Traumatology, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy
| | - Lingxin Zhang
- Department of Pathology and Laboratory Medicine, Sinai Health System, Toronto, Canada
| | - Zhidao Xia
- Centre for Nanohealth, Swansea University Medical School, Singleton Park, Swansea, UK
| | - Jiri Gallo
- Department of Orthopaedics, Faculty of Medicine and Dentistry, University Hospital, Palacky University Olomouc, Czech Republic
| | - Shonali Natu
- Department of Pathology, University Hospital of North Tees and Hartlepool NHS Foundation Trust, Stockton-on-Tees, UK
| | - David Langton
- Orthopaedic Department, Freeman Hospital, Newcastle upon Tyne, UK
| | - Monika Huber
- Pathologisch-bakteriologisches Institut, Otto Wagner Spital, Wien, Austria
| | - Anastasia Rakow
- Department of Orthopedics and Orthopedic Surgery, University Medicine Greifswald, Greifswald, Germany
| | - Janosch Schoon
- Department of Orthopedics and Orthopedic Surgery, University Medicine Greifswald, Greifswald, Germany
| | - Enrique Gomez-Barrena
- Servicio de Cirugía Ortopédica y Traumatología, Hospital Universitario La Paz-IdiPAZ, Universidad Autónoma de Madrid, Madrid, Spain
| | - Veit Krenn
- MVZ-Zentrum für Histologie, Zytologie und Molekulare Diagnostik-GmbH, Trier, Germany
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8
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Welles TS, Ahn J. Investigation of the effects of electrochemical reactions on complex metal tribocorrosion within the human body. Heliyon 2021; 7:e07023. [PMID: 34041392 PMCID: PMC8144002 DOI: 10.1016/j.heliyon.2021.e07023] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/13/2020] [Accepted: 05/05/2021] [Indexed: 11/24/2022] Open
Abstract
Although total hip arthroplasty (THA) is considered to be the most successful orthopedic operation in restoring mobility and relieving pain, common Metal-on-Metal (MoM) implants developed in the past decade suffer from severe inflammatory reactions of the surrounding tissue caused by the premature corrosion and degradation of the implant. A substantial amount of research has been dedicated to the investigation of mechanically driven fretting and crevice corrosion as the primary mechanism of implant failure. However, the exact mechanism by which hip implant breakdown occurs remains unknown, as current in vitro fretting and crevice corrosion studies have failed to completely replicate the corrosion characteristics of recovered implants. Here, we show that minor electric potential oscillations on a model hip implant replicate the corrosion of failed implants without the introduction of mechanical wear. We found in a controlled lab setting that small electrical oscillations, of similar frequency and magnitude as those resulting from ambient electromagnetic waves interacting with the metal of the implant, can force electrochemical reactions within a simulated synovial fluid environment that have not been previously predicted. In lab testing we have shown the replication of titanium, phosphorous, and oxygen deposition onto the surface of ASTM astm:F75 CoCrMo metal alloy test specimens, matching the chemical composition of previously retrieved wear particles from failed patient prosthetics. Our results demonstrate that the electrical activity and ensuing electrochemical activity excites two corrosion failure modes: direct dissolution of the medically implantable alloy, leaching metal ions into the body, and surface deposition growth, forming the precursor of secondary wear particles. We anticipate our findings to be the foundation for the future development and testing of electrochemically resistant implantable material.
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Affiliation(s)
- Thomas S. Welles
- Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY 13244-1240, USA
| | - Jeongmin Ahn
- Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY 13244-1240, USA
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9
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Cobalt–Chromium Dental Alloys: Metal Exposures, Toxicological Risks, CMR Classification, and EU Regulatory Framework. CRYSTALS 2020. [DOI: 10.3390/cryst10121151] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
During the 20th century, metal alloys have assumed an important role as restorative materials. Among existing examples, cobalt–chromium (Co–Cr) alloys increasingly began to be used in medicine and especially in dentistry. Their success is mainly due to their mechanical properties such as stiffness, strength and corrosion resistance, thus allowing a high biocompatibility. There are quite meaningful data on the corrosion and toxicity of Co–Cr alloys for their use in restorative materials such as dental prostheses. Toxicological studies following Co and Cr exposures in the oral cavity are more difficult to conduct because there are many different situations leading to the release of metal ions and wear particles. Furthermore, the links between exposure and the appearance of local or systemic toxicity are not automatic. Since 2017, the European Union (EU) regulatory framework for Co–Cr alloys has been undergoing profound changes. A new EU Medical Devices Regulation (MDR) (2017/745) will be applied in May 2021 with the need to consider that Co metal is a new carcinogenic, mutagenic and toxic to reproduction (CMR) substance. On 18 February 2020, the 14th Adaptation to Technical Progress (ATP14) to the Classification, Labelling and Packaging (CLP) regulation was published, including the harmonised classification for Co metal as a CMR 1B substance. In this context, the use of Co might be forbidden if the medical devices are invasive and as soon as they include more than 0.1% (m/m) Co. This review provides a specific overview on Co–Cr dental alloys in terms of metal ions and wear particles release, toxicological risks, and the actual and new EU regulatory framework.
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10
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Crainic AM, Callisti M, van Veelen A, Michalik A, Milton JA, Palmer MR, Cook RB. A comparative study on the physicochemical characteristics of nanoparticles released in vivo from CoCrMo tapers and cement-stem interfaces of total hip replacements. J Biomed Mater Res B Appl Biomater 2020; 108:3311-3322. [PMID: 32596955 DOI: 10.1002/jbm.b.34667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 04/24/2020] [Accepted: 05/25/2020] [Indexed: 11/09/2022]
Abstract
The good biocompatibility and corrosion resistance of the bulk CoCrMo alloy has resulted in it being used in the manufacture of implants and load bearing medical devices. These devices, however, can release wear and corrosion products which differ from the composition of the bulk CoCrMo alloy. The physicochemical characteristics of the particles and the associated in vivo reactivity are dictated by the wear mechanisms and electrochemical conditions at the sites of material loss. Debris released from CoCrMo hip bearings, taper junctions, or cement-stem interfaces can, therefore, have different chemical and morphological characteristics, which provide them with different in vivo toxicities. Here, we propose to assess and compare the characteristics of the particles released in vivo from CoCrMo tapers and cement-stem interfaces which have received less attention compared to debris originating from the hip bearings. The study uses state-of-art characterization techniques to provide a detailed understanding of the size, morphology, composition, and chemistry of the particles liberated from the wear and corrosion flakes from revised hip replacements, with an enzymatic treatment. The phase analyses identified Cr2 O3 nanoparticles released from tapers and cement-stem interfaces, whose composition did not vary with origin or particle morphology. The size distributions showed significantly smaller particles were released from the stems, compared to the particles originating from the corresponding tapers. The investigation demonstrates that the tribocorrosive processes occurring at the taper and stem interfaces both result in Cr2 O3 nanoparticle formation.
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Affiliation(s)
- Alina M Crainic
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, Southampton, UK
| | - Mauro Callisti
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, Southampton, UK.,Department of Materials Science and Metallurgy, Cambridge University, Cambridge, UK
| | - Arjen van Veelen
- Material Science and Technology Division, Material Science and Technology Division, Los Alamos, NM 87545, UK.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025
| | - Agnes Michalik
- National Oceanography Centre Southampton (NOCS), University of Southampton, School of Ocean and Earth Science, Southampton, UK
| | - James A Milton
- National Oceanography Centre Southampton (NOCS), University of Southampton, School of Ocean and Earth Science, Southampton, UK
| | - Martin R Palmer
- National Oceanography Centre Southampton (NOCS), University of Southampton, School of Ocean and Earth Science, Southampton, UK
| | - Richard B Cook
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, Southampton, UK
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11
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Ion-exchange HPLC-ICP-MS: A new window to chromium speciation in biological tissues. Talanta 2020; 218:121150. [PMID: 32797905 DOI: 10.1016/j.talanta.2020.121150] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 05/05/2020] [Accepted: 05/09/2020] [Indexed: 01/27/2023]
Abstract
The presented work proposes a novel analytical ICP-MS-based approach for the accurate and precise chromium speciation in biological tissues. The determination of total Cr(VI) and soluble Cr(III) species was carried out by alkaline EDTA extraction followed by their separation using ion-exchange high-performance liquid chromatography inductively coupled plasma mass spectrometry (IE-HPLC-ICP-MS). The developed method was validated according to the procedure given in the United States Food and Drug Administration guideline on the validation of bioanalytical methods. Validation parameters included limit of detection (≤ 0.03 μg g-1), limit of quantification (≤ 0.08 μg g-1), linearity (r ≥ 0.9998), intra-day and inter-day accuracy (86-110%) and precision (≤ 10%), extraction recovery (89-110%), carry-over effect and sensitivity. In addition, special attention was paid to the study of chromium species interconversion and the elimination of spectral interferences. Moreover, the validated ICP-MS method employing microwave acid digestion was used to determine the total Cr content in collected fractions. Finally, the whole ICP-MS-based methodology was applied to the analyses of two certified reference materials of hepatopancreas tissue. Obtained results indicated that the majority of chromium in biological tissues is bound to the solid residue, Cr(VI) was determined in none of the samples investigated. This is the first study focusing on soluble Cr(III), total Cr(VI), and total bound Cr species in biological tissues. It is characterized by efficient sample preparation and fast simultaneous analysis of Cr species with parallel total Cr analysis serving for chromium balance evaluation.
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12
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Balachandran S, Zachariah Z, Fischer A, Mayweg D, Wimmer MA, Raabe D, Herbig M. Atomic Scale Origin of Metal Ion Release from Hip Implant Taper Junctions. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:1903008. [PMID: 32154080 PMCID: PMC7055581 DOI: 10.1002/advs.201903008] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 12/30/2019] [Indexed: 06/10/2023]
Abstract
Millions worldwide suffer from arthritis of the hips, and total hip replacement is a clinically successful treatment for end-stage arthritis patients. Typical hip implants incorporate a cobalt alloy (Co-Cr-Mo) femoral head fixed on a titanium alloy (Ti-6Al-4V) femoral stem via a Morse taper junction. However, fretting and corrosion at this junction can cause release of wear particles and metal ions from the metallic implant, leading to local and systemic toxicity in patients. This study is a multiscale structural-chemical investigation, ranging from the micrometer down to the atomic scale, of the underlying mechanisms leading to metal ion release from such taper junctions. Correlative transmission electron microscopy and atom probe tomography reveals microstructural and compositional alterations in the subsurface of the titanium alloy subjected to in vitro gross-slip fretting against the cobalt alloy. Even though the cobalt alloy is comparatively more wear-resistant, changes in the titanium alloy promote tribocorrosion and subsequent degradation of the cobalt alloy. These observations regarding the concurrent occurrence of electrochemical and tribological phenomena are vital to further improve the design and performance of taper junctions in similar environments.
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Affiliation(s)
- Shanoob Balachandran
- Department Microstructure Physics and Alloy DesignMax‐Planck‐Institut für Eisenforschung GmbHMax‐Planck‐Straße 1Düsseldorf40237Germany
| | - Zita Zachariah
- Department Microstructure Physics and Alloy DesignMax‐Planck‐Institut für Eisenforschung GmbHMax‐Planck‐Straße 1Düsseldorf40237Germany
| | - Alfons Fischer
- Department Microstructure Physics and Alloy DesignMax‐Planck‐Institut für Eisenforschung GmbHMax‐Planck‐Straße 1Düsseldorf40237Germany
- Department of Orthopedic SurgeryRush University Medical Center1611 W. Harrison St.ChicagoIL60612USA
| | - David Mayweg
- Department Microstructure Physics and Alloy DesignMax‐Planck‐Institut für Eisenforschung GmbHMax‐Planck‐Straße 1Düsseldorf40237Germany
| | - Markus A. Wimmer
- Department of Orthopedic SurgeryRush University Medical Center1611 W. Harrison St.ChicagoIL60612USA
| | - Dierk Raabe
- Department Microstructure Physics and Alloy DesignMax‐Planck‐Institut für Eisenforschung GmbHMax‐Planck‐Straße 1Düsseldorf40237Germany
| | - Michael Herbig
- Department Microstructure Physics and Alloy DesignMax‐Planck‐Institut für Eisenforschung GmbHMax‐Planck‐Straße 1Düsseldorf40237Germany
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13
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Liu S, Hall DJ, McCarthy SM, Jacobs JJ, Urban RM, Pourzal R. Fourier transform infrared spectroscopic imaging of wear and corrosion products within joint capsule tissue from total hip replacements patients. J Biomed Mater Res B Appl Biomater 2019; 108:513-526. [PMID: 31099981 DOI: 10.1002/jbm.b.34408] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 03/04/2019] [Accepted: 04/26/2019] [Indexed: 12/15/2022]
Abstract
Implant debris generated by wear and corrosion is a prominent cause of joint replacement failure. This study utilized Fourier transform infrared spectroscopic imaging (FTIR-I) to gain a better understanding of the chemical structure of implant debris and its impact on the surrounding biological environment. Therefore, retrieved joint capsule tissue from five total hip replacement patients was analyzed. All five cases presented different implant designs and histopathological patterns. All tissue samples were formalin-fixed and paraffin-embedded. Unstained, 5 μm thick sections were prepared. The unstained sections were placed on BaF2 windows and deparaffinized with xylene prior to analysis. FTIR-I data were collected at a spectral resolution of 4 cm-1 using an Agilent Cary 670 spectrometer coupled with Cary 620 FTIR microscope. The results of study demonstrated that FTIR-I is a powerful tool that can be used complimentary to the existing histopathological evaluation of tissue. FTIR-I was able to distinguish areas with different cell types (macrophages, lymphocytes). Small, but distinct differences could be detected depending on the state of cells (viable, necrotic) and depending on what type of debris was present (polyethylene [PE], suture material, and metal oxides). Although, metal oxides were mainly below the measurable range of FTIR-I, the infrared spectra of tissues exhibited noticeable difference in their presence. Tens of micrometer sized polyethylene particles could be easily imaged, but also accumulations of submicron particles could be detected within macrophages. FTIR-I was also able to distinguish between PE debris, and other birefringent materials such as suture. Chromium-phosphate particles originating from corrosion processes within modular taper junctions of hip implants could be identified and easily distinguished from other phosphorous materials such as bone. In conclusion, this study successfully demonstrated that FTIR-I is a useful tool that can image and determine the biochemical information of retrieved tissue samples over tens of square millimeters in a completely label free, nondestructive, and objective manner. The resulting chemical images provide a deeper understanding of the chemical nature of implant debris and their impact on chemical changes of the tissue within which they are embedded.
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Affiliation(s)
- Songyun Liu
- Department of Bioengineering, University of Illinois at Chicago, 851 S Morgan St, Chicago, IL 60607, USA.,Department of Orthopedic Surgery, Rush University Medical Center, 1611W Harrison Street, Suite 200, Chicago, IL 60612, USA
| | - Deborah J Hall
- Department of Orthopedic Surgery, Rush University Medical Center, 1611W Harrison Street, Suite 200, Chicago, IL 60612, USA
| | - Stephanie M McCarthy
- Department of Orthopedic Surgery, Rush University Medical Center, 1611W Harrison Street, Suite 200, Chicago, IL 60612, USA
| | - Joshua J Jacobs
- Department of Orthopedic Surgery, Rush University Medical Center, 1611W Harrison Street, Suite 200, Chicago, IL 60612, USA
| | - Robert M Urban
- Department of Orthopedic Surgery, Rush University Medical Center, 1611W Harrison Street, Suite 200, Chicago, IL 60612, USA
| | - Robin Pourzal
- Department of Orthopedic Surgery, Rush University Medical Center, 1611W Harrison Street, Suite 200, Chicago, IL 60612, USA
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14
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Perino G, Sunitsch S, Huber M, Ramirez D, Gallo J, Vaculova J, Natu S, Kretzer JP, Müller S, Thomas P, Thomsen M, Krukemeyer MG, Resch H, Hügle T, Waldstein W, Böettner F, Gehrke T, Sesselmann S, Rüther W, Xia Z, Purdue E, Krenn V. Diagnostic guidelines for the histological particle algorithm in the periprosthetic neo-synovial tissue. BMC Clin Pathol 2018; 18:7. [PMID: 30158837 PMCID: PMC6109269 DOI: 10.1186/s12907-018-0074-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 08/16/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND The identification of implant wear particles and non-implant related particles and the characterization of the inflammatory responses in the periprosthetic neo-synovial membrane, bone, and the synovial-like interface membrane (SLIM) play an important role for the evaluation of clinical outcome, correlation with radiological and implant retrieval studies, and understanding of the biological pathways contributing to implant failures in joint arthroplasty. The purpose of this study is to present a comprehensive histological particle algorithm (HPA) as a practical guide to particle identification at routine light microscopy examination. METHODS The cases used for particle analysis were selected retrospectively from the archives of two institutions and were representative of the implant wear and non-implant related particle spectrum. All particle categories were described according to their size, shape, colour and properties observed at light microscopy, under polarized light, and after histochemical stains when necessary. A unified range of particle size, defined as a measure of length only, is proposed for the wear particles with five classes for polyethylene (PE) particles and four classes for conventional and corrosion metallic particles and ceramic particles. RESULTS All implant wear and non-implant related particles were described and illustrated in detail by category. A particle scoring system for the periprosthetic tissue/SLIM is proposed as follows: 1) Wear particle identification at light microscopy with a two-step analysis at low (× 25, × 40, and × 100) and high magnification (× 200 and × 400); 2) Identification of the predominant wear particle type with size determination; 3) The presence of non-implant related endogenous and/or foreign particles. A guide for a comprehensive pathology report is also provided with sections for macroscopic and microscopic description, and diagnosis. CONCLUSIONS The HPA should be considered a standard for the histological analysis of periprosthetic neo-synovial membrane, bone, and SLIM. It provides a basic, standardized tool for the identification of implant wear and non-implant related particles at routine light microscopy examination and aims at reducing intra-observer and inter-observer variability to provide a common platform for multicentric implant retrieval/radiological/histological studies and valuable data for the risk assessment of implant performance for regional and national implant registries and government agencies.
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Affiliation(s)
- G. Perino
- Department of Pathology and Laboratory Medicine, Hospital for Special Surgery, 535 E 70th Street, New York, NY 10023 USA
| | - S. Sunitsch
- Medizinische Universität Graz, Institut für Pathologie, Graz, Austria
| | - M. Huber
- Pathologisch-bakteriologisches Institut, Otto Wagner Spital, Wien, Austria
| | - D. Ramirez
- Department of Pathology and Laboratory Medicine, Hospital for Special Surgery, 535 E 70th Street, New York, NY 10023 USA
| | - J. Gallo
- Department of Orthopaedics, Faculty of Medicine and Dentistry, University Hospital, Palacky University Olomouc, Olomouc, Czech Republic
| | - J. Vaculova
- Department of Pathology, Fakultni Nemocnice Ostrava, Ostrava, Czech Republic
| | - S. Natu
- Department of Pathology, University hospital of North Tees and Hartlepool NHS Foundation Trust, Stockton-on-Tees, UK
| | - J. P. Kretzer
- Labor für Biomechanik und Implantat-Forschung, Klinik für Orthopädie und Unfallchirurgie, Universitätsklinikum Heidelberg, Heidelberg, Germany
| | - S. Müller
- MVZ-Zentrum für Histologie, Zytologie und Molekulare Diagnostik, Trier, Germany
| | - P. Thomas
- LMU Klinik, Klinik und Poliklinik für Dermatologie und Allergologie, Munich, Germany
| | - M. Thomsen
- Baden-Baden Klinik, Baden-Baden, Germany
| | | | - H. Resch
- Universitätsklinik für Unfallchirurgie und Sporttraumatologie, Salzburg, Austria
| | - T. Hügle
- Hôpital Orthopédique, Lausanne, Switzerland
| | - W. Waldstein
- Medizinische Universität Wien, AKH-Wien, Universitätsklinik für Orthopädie, Wien, Austria
| | - F. Böettner
- Adult Reconstruction and Joint Replacement Division, Hospital for Special Surgery, New York, NY USA
| | - T. Gehrke
- Helios Endo-Klinik, Hamburg, Germany
| | - S. Sesselmann
- Orthopädische Universitätsklinik Erlangen, Erlangen, Germany
| | - W. Rüther
- Klinik und Poliklinik für Orthopädie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Z. Xia
- Centre for Nanohealth, Swansea University Medical School, Singleton Park, Swansea, UK
| | - E. Purdue
- Hospital for Special Surgery, Research Institute, New York, NY USA
| | - V. Krenn
- MVZ-Zentrum für Histologie, Zytologie und Molekulare Diagnostik, Trier, Germany
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15
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Crainic AM, Callisti M, Palmer MR, Cook RB. Investigation of nano-sized debris released from CoCrMo secondary interfaces in total hip replacements: Digestion of the flakes. J Biomed Mater Res B Appl Biomater 2018; 107:424-434. [PMID: 29663665 DOI: 10.1002/jbm.b.34134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 02/27/2018] [Accepted: 03/23/2018] [Indexed: 11/06/2022]
Abstract
The in vivo release of wear debris and corrosion products from the metallic interfaces of total hip replacements is associated with a wide spectrum of adverse body reactions and systemic manifestations. The origin of debris and the electrochemical conditions at the sites of material loss both play a role in determining the physicochemical characteristics of the particles, and thus influence their in vivo reactivity. Debris retrieved from revised CoCrMo tapers and cement-stem interfaces consists of heterogeneous flakes that comprise mechanically mixed metal particles, corrosion products and organic material. Detailed investigation of the size and composition of the metal debris contained within these composites requires the digestion of the flakes to release the small metal particles. Here, we compare alkaline and enzymatic digestion methods that both aim to fragment the flakes and reveal their smallest building blocks. The characterization of debris cleaned with both methods revealed crystalline Cr oxide nanoparticles and clusters. Comparison between the treatments showed that the alkaline method is more efficient in fragmenting the flakes and provided cleaner and generally smaller nanoparticles than exhibited in debris released with the enzymatic treatment. The provision of cleaner nanoparticles from the alkaline method also allows the physicochemical properties of the particles to be more clearly identified. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 424-434, 2019.
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Affiliation(s)
- Alina M Crainic
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, University Road, Southampton, SO17 1BJ, UK
| | - Mauro Callisti
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, University Road, Southampton, SO17 1BJ, UK.,Department of Materials Science and Metallurgy, Cambridge University, Cambridge, CB3 0FS, UK
| | - Martin R Palmer
- School of Ocean and Earth Science, National Oceanography Centre Southampton (NOCS), University of Southampton, European Way, Southampton, SO14 3ZH, UK
| | - Richard B Cook
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, University Road, Southampton, SO17 1BJ, UK
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16
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Swiatkowska I, Mosselmans JFW, Geraki T, Wyles CC, Maleszewski JJ, Henckel J, Sampson B, Potter DB, Osman I, Trousdale RT, Hart AJ. Synchrotron analysis of human organ tissue exposed to implant material. J Trace Elem Med Biol 2018; 46:128-137. [PMID: 29413102 DOI: 10.1016/j.jtemb.2017.12.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/19/2017] [Accepted: 12/21/2017] [Indexed: 11/16/2022]
Abstract
BACKGROUND Orthopaedic implants made of cobalt-chromium alloy undergo wear and corrosion that can lead to deposition of cobalt and chromium in vital organs. Elevated cardiac tissue cobalt levels are associated with myocardial injury while chromium is a well-established genotoxin. Though metal composition of tissues surrounding hip implants has been established, few investigators attempted to characterize the metal deposits in systemic tissues of total joint arthroplasty patients. METHODS We report the first use of micro-X-ray fluorescence coupled with micro-X-ray absorption spectroscopy to probe distribution and chemical form of cobalt, chromium and titanium in postmortem samples of splenic, hepatic and cardiac tissue of patients with metal-on-polyethylene hip implants (n = 5). RESULTS Majority of the cobalt was in the 2+ oxidation state, while titanium was present exclusively as titanium dioxide, in either rutile or anatase crystal structure. Chromium was found in a range of forms including a highly oxidised, carcinogenic species (CrV/VI), which has never been identified in human tissue before. CONCLUSIONS Carcinogenic forms of chromium might arise in vital organs of total joint arthroplasty patients. Further studies are warranted with patients with metal-on-metal implants, which tend to have an increased release of cobalt and chromium compared to metal-on-polyethylene hips.
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Affiliation(s)
- Ilona Swiatkowska
- Institute of Orthopaedics and Musculoskeletal Science, University College London, HA7 4LP Stanmore, UK.
| | - J Fred W Mosselmans
- Diamond Light Source, Harwell Science and Innovation Campus, OX11 0DE Didcot, UK
| | - Tina Geraki
- Diamond Light Source, Harwell Science and Innovation Campus, OX11 0DE Didcot, UK
| | - Cody C Wyles
- Mayo Clinic, 200 1st Street SW, Rochester, MN, USA
| | | | - Johann Henckel
- Royal National Orthopaedic Hospital, HA7 4LP Stanmore, UK
| | - Barry Sampson
- Trace Element Laboratory, Department of Clinical Chemistry, Charing Cross Hospital, Imperial College NHS Healthcare Trust, W6 8RF London, UK
| | - Dominic B Potter
- Departament of Chemistry, University College London, WC1H 0AJ London, UK
| | - Ibtisam Osman
- Trace Element Laboratory, Department of Clinical Chemistry, Charing Cross Hospital, Imperial College NHS Healthcare Trust, W6 8RF London, UK
| | | | - Alister J Hart
- Institute of Orthopaedics and Musculoskeletal Science, University College London, HA7 4LP Stanmore, UK; Royal National Orthopaedic Hospital, HA7 4LP Stanmore, UK
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