Cobalt Chrome Molybdenum Research Articles

Reactive oxygen species, electrode potential and pH affect CoCrMo alloy corrosion and semiconducting behavior in simulated inflammatory environments

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 significanceCorrosion 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.

A unique tribological inverted bearing solution for reverse shoulder arthroplasty: Vitamin E and ceramic (unique inverse pairings in rTSR)

Background Reverse total shoulder arthroplasty has gained popularity for various shoulder conditions and has evolved over time to accommodate for material changes and design philosophy including inverse materials. The tribological behaviour of shoulder arthroplasty has been extensively studied in relation to biological osteolysis which is a notable concern regarding component loosening. Methods This study aims to assess the wear performance of a vitamin E-stabilised glenosphere or conventional ultra-high-molecular-weight polyethylene glenosphere whilst paired with ceramic or cobalt–chrome–molybdenum inlay in a shoulder joint wear simulator. A cumulative total of five million cycles was utilised with gravimetric and visual analysis of wear. Results Gravimetric wear was observed to be the lowest when a vitamin E-stabilised glenosphere was paired with a ceramic inlay – demonstrating the greatest wear resistance. Conclusion Our results demonstrate that the combination of vitamin E-stabilised polyethylene glenosphere and ceramic inlay has improved wear resistance properties in load simulations when compared to other bearing surface combinations. This supports the use of the novel inverse combination in clinical practice to attain longer-term survivorship in reverse total shoulder replacements. Level of evidence Basic Science Study; Tribology

Functional characterization of biomechanical loading and biocorrosion resistance properties of novel additively manufactured porous CoCrMo implant: Comparative analysis with gyroid and rhombic dodecahedron

Notably, successful clinical outcomes of additively manufactured porous metallic implants require careful consideration of factors such as porosity, pore size, and pore interconnectivity. Applying the SLM technique in Cobalt chrome molybdenum (CoCrMo) alloy fabrication has shown excellent results for prosthetic restorations. However, the corrosion performance of 3D-printed interpenetrating lattices or a combination of minimal surface and strut lattices such as BD.05 (both based on TPMS and struts lattice cells) remains unexplored. This study explores additively manufactured BD.05 structures using CoCrMo as a bulk biomaterial to address the stiffness mismatch, a common cause of stress shielding between implants and bones. Comparative characterization of TPMS-based gyroid and stress lattice-based Rhombic dodecahedron (RH) shows a distinct deformation pattern under quasi-compressive loading. The gyroid exhibits higher yield stress (126.05 MPa), followed by BD-0.5 (25.46 MPa) and RH (9.36 MPa). BD.05 shows an impact strength of 3.17 ± 0.03J/cm2 and a microhardness of 556HV1. Electrochemical measurements demonstrate the inherent corrosion resistance of the fabricated structures. This indicates the appropriate and successful promise of these lightweight interpenetrating-based lattice metamaterial implants in orthopedic applications.

FE Investigation of Design and Quality Control-Related Issues Contributing to Metal-On-Metal Hip Implant Failures

High levels of cobalt and chromium ions were detected in the bodies of multiple recipients of modular cobalt chrome molybdenum metal-on-metal hip implants, necessitating the revision of their implants. A forensic engineering investigation of provided discovery documents and existing literature regarding the design, manufacturing, and clinical testing of these modular hip implants was performed. The investigation revealed that the modular interfaces of the implant allowed for micromotion to induce mechanically assisted crevice corrosion at these surfaces. The debris from this corrosion resulted in the release of metal ions into the bodies of the users, forming pseudotumors and compromising the user’s health and wellbeing. The effect of this corrosion was enhanced by the galvanic couple that existed between the modular components of the implant. In addition, scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) analysis identified silicon carbide (SiC) and aluminum oxide (AL2O3 ) particles left behind from polishing, which were embedded in the ball and liners. These particles accelerated the wear of the hip implant and further exacerbated the release of metal ions. The designers of future hip implants should take care in preventing the occurrence of the above-stated factors.

Highly lubricious SPMK-g-PEEK implant surfaces to facilitate rehydration of articular cartilage

To enable long lasting osteochondral defect repairs which preserve the native function of synovial joint counter-face, it is essential to develop surfaces which are optimised to support healthy cartilage function by providing a hydrated, low friction and compliant sliding interface. PEEK surfaces were modified using a biocompatible 3-sulfopropyl methacrylate potassium salt (SPMK) through UV photo-polymerisation, resulting in a ∼350 nm thick hydrophilic coating rich in hydrophilic anionic sulfonic acid groups. Characterisation was done through Fourier Transformed Infrared Spectroscopy, Focused Ion Beam Scanning Electron Microscopy, and Water Contact Angle measurements.Using a Bruker UMT TriboLab, bovine cartilage sliding tests were conducted with real-time strain and shear force measurements, comparing untreated PEEK, SPMK functionalised PEEK (SPMK-g-PEEK), and Cobalt Chrome Molybdenum alloy. Tribological tests over 2.5 h at physiological loads (0.75 MPa) revealed that SPMK-g-PEEK maintains low friction (μ< 0.024) and minimises equilibrium strain, significantly reducing forces on the cartilage interface. Post-test analysis showed no notable damage to the cartilage interfacing against the SPMK functionalised surfaces.The application of a constitutive biphasic cartilage model to the experimental strain data reveals that SPMK surfaces increase the interfacial permeability of cartilage in sliding, facilitating fluid and strain recovery. Unlike previous demonstrations of sliding-induced tribological rehydration requiring specific hydrodynamic conditions, the SPMK-g-PEEK introduces a novel mode of tribological rehydration operating at low speeds and in a stationary contact area. SPMK-g-PEEK surfaces provide an enhanced cartilage counter-surface, which provides a highly hydrated and lubricious boundary layer along with supporting biphasic lubrication.Soft polymer surface functionalisation of orthopaedic implant surfaces are a promising approach for minimally invasive synovial joint repair with an enhanced bioinspired polyelectrolyte interface for sliding against cartilage. These hydrophilic surface coatings offer an enabling technology for the next generation of focal cartilage repair and hemiarthroplasty implant surfaces.

Comparative Evaluation of Carbon Reinforced Polyetherketone Acetabular Cup using Finite Element Analysis.

Background: Patients suffering from osteoarthritis undergo surgery to replace hip joints with hip prosthesis implants. Today most acetabular cups of hip prostheses are made of Ultra-High-Molecular-Weight-Polyethylene. However, these materials acting as acetabular cups of the implant have been recalled since patients have been feeling uncomfortable and abstained from physical activities. A newly introduced material, 30% Carbon Reinforced Polyetherketone, possess better isotropic mechanical properties and lower wear rates.Objective: The research aims to compare the von-Mises stresses and deformation in static and dynamic loading of Ultra-High Molecular-Weight-Polyethylene to 30% Reinforced Carbon Fiber Polyetherketone using Finite Element Analysis.Material and Methods: An analytical study was performed to evaluate material selection and their contact performances of acetabular cups. Four pairs have been analyzed under loading conditions following ASTM F2996-13 and ISO 7206-4 standards. The acetabular cups options are made of 30% Carbon Reinforced Fiber Polyetherketone or Ultra-High-Molecular-Weight-Polyethylene. Besides, the femoral head and steam options are either Alumina Ceramic or Cobalt Chrome Molybdenum. Results: The yield strength of Ultra-High-Molecular-Weight-Polyethylene is considerably small, resulting in the acetabular cup to fail when applied to high loading conditions. Carbon Reinforced Polyetherketone with Alumina Ceramic yielded 65% lower deformation at stumbling phase. Conclusion: Since the study focuses on linear isotropic material properties, Alumina Ceramic dominates a higher elastic modulus than Cobalt Chrome Molybdenum, nominating it the best fit combination for lower von-Mises stresses, acting on the Carbon Reinforced Polyetherketone acetabular cup.

Experimental investigation of biological and mechanical properties of CoCrMo based selective laser melted metamaterials for bone implant manufacturing

Abstract Metamaterials are composed of structural elements and their properties are derived mainly from the inner structure of the elements, rather than the properties of their constituent material. In this study, mechanical and biological properties of metamaterial made by selective laser melted cobalt chrome molybdenum (CoCrMo) were studied. Metamaterials of diamond and square shapes unit cells with 1.5–2.5 mm strut length and 0.4–0.6 mm strut thickness was prepared by layer-by-layer additive manufacturing technique. The metamaterials demonstrated excellent biological property under MTT assay cytotoxicity after 14 days cell cultured. Comparisons of the experimental data between two unit cell types made by compression tests exhibited that the stiffness of square shape is always higher 20% than those of diamond type, nonetheless all the tested materials satisfy the young’s modulus of human cancellous bone. Furthermore, the compression tests also resulted in determining both unit cell types with strut thickness 0.6 mm and strut length 1.5 mm to meet the compressive strength of human cortical bone. The tailored metamaterials by modifying the unit cell sizes and shapes of fabricated bone implant can be achieved by using additive manufacturing technique. The design concepts of internal structures by determining the properties of metamaterials demonstrated in this study will be valuable in future biomedical applications.

Influence of Mangan on Structure and Corrosion Properties of Cobalt Chrome Molybdenum (Co-Cr-Mo)

Co-Cr-Mo alloy are usually used as implant materials in biomedical application. Corrosion resistance is one of the properties needed to full fill the requirement. The nature of material resistance in the body (biocompatibility) is determined by the corrosion resistance of a biomaterial. Corrosion which emits metal ions in the tissue directed at the implant and activates the system in the body. Mangan (Mn) were added to this alloy to enhance corrosion resistance. Addition of Mangan (Mn) might also affect to the structure of this alloy. X ray diffraction and Electrochemical experiment were conducted to characterized the structure and corrosion resistance of this alloy. The addition of Manganase shows significant influence on the structure and corrosion resistance on the Co-Cr-Mo alloy.

The Effect of Manganese and Heat treatment on Structure and Corrosion Resistance of Cobalt Chrome Molybdenum

The selection of implant biomaterials must be based on the compatibility of the human body so that it has significant properties that will last long without experiencing rejection during use in the body. One of the commonly used for biomedical implants is Co-Cr-Mo alloy. Since these alloy should also fulfill implant requirements such as high corrosion resistance. To increase corrosion resistance, the heat treatment temperature and time (heat treatment parameters) were 65 hours at 700 °C. Characterization was performed using X-ray diffraction and Potensio dynamic. The different X-ray diffraction patterns and corrosion resistance were obtained. The results show both structure and corrosion resistance are markedly influenced by the addition of Manganese after heat treatment.

Fabricating Laser-Induced Periodic Surface Structures on Medical Grade Cobalt–Chrome–Molybdenum: Tribological, Wetting and Leaching Properties

Hip-implants structured with anti-bacterial textures should show a low-friction coefficient and should not leach hazardous substances into the human body. The surface of a typical material used for hip-implants, namely Cobalt–Chrome–Molybdenum (CoCrMo) was textured with different types of laser-induced periodic surface structures (LIPSS)—i.e., low spatial frequency LIPSS (LSFL), hierarchical structures consisting of grooves superimposed with high spatial frequency LIPSS (HSFL) and Triangular shaped Nanopillars (TNP)—using a picosecond pulsed laser source. The effect of LIPSS on the wettability, friction, as well as wear of the structures, when slid against a polyethylene (PE) counter surface and biocompatibility was analyzed. Surfaces covered with LSFL show superhydrophobicity and grooves with superimposed HSFL, as well as TNP, show hydrophobic behavior. The coefficient of friction (CoF) of LIPSS against a polyethylene (PE) counter surface was found to be higher (ranging from 0.40 to 0.66) than the CoF of (polished) CoCrMo, which was found to equal 0.22. It was found that the samples release cobalt within biocompatible limits. Compared to polished reference surfaces, LIPSS cause higher friction of CoCrMo against PE contact. However, the wear of the PE counter surface only increased significantly for the LSFL textures. For these reasons, it is concluded that LIPSS are not suitable for a heavily loaded metal-on-plastic bearing contact.

Effect of sintering temperature on physical properties & hardness of CoCrMo alloys fabricated by metal injection moulding process

Metal Injection Moulding (MIM) process is one of the Powder Metallurgy manufacturing techniques utilised to produce Cobalt Chromium Molybdenum (CoCrMo) compacts. The objective of this study is to determine physical properties and hardness of CoCrMo alloy compact sintered at three different sintering temperature at the similar soaking time. At the beginning, sample were fabricated by using Injection Moulding machine. Cobalt Chrome Molybdenum (CoCrMo) metal powder was selected for this study. A morphological study was conducted using optical microscope (OM) and micro-Vickers hardness testing. From the result obtained, it shows upward trend either on the hardness or physical properties of the samples. CoCrMo sintered compact become harder and volume of pores on surface become less due to the increase on sintering temperature. However, effect of increasing sintering temperature shows significant shrinkage of the sample, beginning losses in dimensional accuracy. It is discovered that a little change in sintering temperature gives significant impact on the microstructure, physical, mechanical of the alloy.

Fundamental mechanisms in orthogonal cutting of medical grade cobalt chromium alloy (ASTM F75)

Cobalt chromium alloys are sui generis materials for orthopaedic implants due mainly to unique properties of biocompatibility and wear resistance in the demanding in-vivo environment. Notwithstanding the importance of both defined and undefined edge cutting processes on form, finish and surface integrity of orthopaedic components, there has been minimal research reported in the public domain on the fundamental mechanisms in cutting of these alloys. Accordingly, this paper reports on initial research into cutting of the biomedical grade cobalt chrome molybdenum (Co-Cr-Mo) alloy, ASTM F75.Following a brief overview of physical and mechanical properties of this class of Co-Cr-Mo alloys, the results of a full factorial, orthogonal cutting experiment are presented. This involved measurement of force components (Ft and Ff) as a function of the undeformed chip thickness (h) and cutting speed (vc) which were varied over ranges from 20 to 140μm and 20 to 60m/min respectively. The results demonstrated an expected linear increase in force components with h at speeds of 20 and 60m/min. However, at the intermediate speed of 40m/min, there was a transition between about 60 and 80μm indicating a discontinuous rather than continuous effect of speed. The results also enabled determination of the cutting force coefficients Ktc, Kte, Kfc and Kfe, as well as ki1,0.1 and mi0.1 of the Kienzle equations. These relations will enable macro-mechanic modelling of more complex cutting operations, such as milling, in the future.

Machinability of Cobalt-based and Cobalt Chromium Molybdenum Alloys - A Review

Cobalt chrome molybdenum alloy is considered as one of the advanced materials which is widely gaining popularity in various engineering and medical applications. However, it is categorized as difficult to machine material due to its unique combination of properties which include high strength, toughness, wear resistance and low thermal conductivity. These properties tend to hinder the machinability of this alloy which results in rapid tool wear and shorter tool life. This paper presents a general review of the materials’ characteristics and properties together with their machinability assessment under various machining conditions. The trend of machining and future researches on cobalt-based and cobalt chromium molybdenum alloys are also discussed adequately.

Influence of Shielding Gas and Mechanical Activation of Metal Powders on the Quality of Surface Sintered Layers

The thesis analyses the influence of argon shielding gas and mechanical activation of PMS-1 copper powder and DSK-F75 cobalt chrome molybdenum powder on the surface sintered layer quality under various sintering conditions. Factors affecting the quality of the sintered surface and internal structure are studied. The obtained results prove positive impact of the shielding gas and mechanical activation. Sintering PMS-1 copper powder in argon shielding gas after mechanical activation leads to reduced internal stresses and roughness, as well as improved strength characteristics of the sintered surface. Analysis of sintered samples of mechanically activated DSK-F75 cobalt chrome molybdenum powder shows that the strength of the sintered surface grows porosity and coagulation changes.

The evolution of polymer wear debris from total disc arthroplasty

Total disc arthroplasty is an alternative to spinal fusion, aimed at preserving flexibility; these devices typically involve a cobalt chrome molybdenum alloy socket articulating against an ultra-high molecular weight polyethylene (UHMWPE) ball. As with all artificial joints, wear debris is of particular concern due to its effect on both implant life and the in vivo biological reactions that can occur.In this paper, a profile of the UHMWPE wear debris generated from disc arthroplasty, tested on a spine simulator, is built with a combination of SEM image analysis tools. SEM images were analysed by computer vision, which allowed size and shape information to be extracted and images to be categorised by the shared topological features on individual wear particles. The computer visions techniques were based on a Scale Invariant Feature Transform (SIFT) to extract key point data from individual images and a Support Vector Decision Machine (SVM) to filter images based on a series of trained parameters. As certain wear particle morphology is predominantly produced by a particular wear regime, grouping wear particles by morphology and size made it possible to infer the relative rates of various wear regimes responsible for wear debris generation. By sampling synovial lubricant at intervals throughout the tribological test, the predominant wear regimes and particle sizes were tracked over the course of the implant life. Wear debris samples were taken at 12 intervals over a 5 million cycle test.The majority of debris was found to be 0.88μm in equivalent circle diameter, with an aspect ratio (defined as the major over the minor diameter of the smallest possible encompassing ellipse of the debris) of 1.55. There was a decreasing trend in average particle size as the number of cycles increased. During the early stages of the test, adhesion and abrasion were dominant in forming particle morphologies, however after 2 million cycles; particles generated as a result of fatigue became the major particle morphology.

Formation of Surface Layer of Cobalt Chrome Molybdenum Powder Products with Differentiation of Laser Sintering Modes

The paper presents results of research on a method of determining a geometric condition of a sintered surface using an instrumental digital microscope. The results of experimental studies of effects of laser irradiation technological modes on roughness of the cobalt chrome molybdenum powder DSK-F75 sintered layer are presented. Differentiation of modes of product surface and its internal volume formation into rough, semi-finishing and finishing are proposed.

A numerical investigation into the influence of the properties of cobalt chrome cellular structures on the load transfer to the periprosthetic femur following total hip arthroplasty

Stress shielding of the periprosthetic femur following total hip arthroplasty is a problem that can promote the premature loosening of femoral stems. In order to reduce the need for revision surgery it is thought that more flexible implant designs need to be considered. In this work, the mechanical properties of laser melted square pore cobalt chrome molybdenum cellular structures have been incorporated into the design of a traditional monoblock femoral stem. The influence of incorporating the properties of cellular structures on the load transfer to the periprosthetic femur was investigated using a three dimensional finite element model. Eleven different stiffness configurations were investigated by using fully porous and functionally graded approaches. This investigation confirms that the periprosthetic stress values depend on the stiffness configuration of the stem. The numerical results showed that stress shielding is reduced in the periprosthetic Gruen zones when the mechanical properties of cobalt chrome molybdenum cellular structures are used. This work identifies that monoblock femoral stems manufactured using a laser melting process, which are designed for reduced stiffness, have the potential to contribute towards reducing stress shielding.

The potential application of a Cobalt Chrome Molybdenum femoral stem with functionally graded orthotropic structures manufactured using Laser Melting technologies

The cementless fixation of porous coated femoral stems is a common technique employed for Total Hip Arthroplasty (THA). With the rate of revision surgery appearing to rise and younger more active patients requiring primary surgery it can be thought that alternative methods for increasing implant longevity need to be considered. The stress shielding of periprosthetic bone still remains a contributing factor to implant loosening, caused through a mismatch in stiffness between the implant and the bone. However, the ability to achieve stiffness matching characteristics is being realised through the use of Additive Layer Manufacturing (ALM) technologies and Functionally Graded Materials (FGM). This paper proposes an alternative design methodology for a monoblock Cobalt Chrome Molybdenum (CoCrMo) femoral stem. It hypothesises that a femoral stem suitable for cementless fixation can be manufactured using Laser Melting (LM) technology offering orthotropic functionally graded porous structures with similar mechanical properties to human bone. The structure and mechanical properties of the natural femur have been used as a basis for the design criteria which hypothesises that through a combination of numerical analysis and physical testing, an optimal design can be proposed to provide a lightweight, customised femoral stem that can reduce the risk of implant loosening through stress shielding whilst maintaining bone-implant interface stability.

Evaluation of the stiffness characteristics of square pore CoCrMo cellular structures manufactured using laser melting technology for potential orthopaedic applications

In order to improve the stress shielding characteristics of orthopaedic devices implants that mimic the mechanical behaviour of bone need to be considered. Additive layer manufacturing processes provide a capability to produce orthopaedic implants with tailored mechanical properties. In this work cobalt chrome molybdenum cellular structures have been designed and manufactured using selective laser melting, with volume based porosity ranging between 25% and 95%. The effective mechanical properties have been determined through uniaxial compression testing and compared to numerical and analytical predictions where differences were observed. Cellular structures have been presented that exhibit similar stiffness and strength characteristics when compared to cortical and cancellous bone in the human femur. An expression has been proposed to predict the effective elastic modulus of cobalt chrome molybdenum cellular structures with volumetric porosity of 65% and above. A finite element modelling technique has been used to demonstrate that structural variation and heterogeneities that are associated with the manufacture of cellular structures can significantly decrease the effective stiffness.

The Mechanical Performance of Cervical Total Disc Replacements In Vivo

Prospective retrieval analysis of Prodisc-C cervical total disc replacements (CTDRs) from 24 explanting surgeons during a 6-year period. To determine the in vivo mechanical performance and fixation to bone of explanted Prodisc-C CTDRs. The nature and quantity of damage sustained by an implanted device has proven to be important in the prediction of clinical longevity. We hypothesized that retrieval analysis of the Prodisc-C will display characteristic modes of wear consistent with increased posterior angulation and translation of the functional spinal unit after resection of the discoligamentous anatomy. Thirty CTDRs from 29 patients (mean age, 45.1 ± 1.9; range, 31-57 yr) after a mean length of implantation of 1.0 ± 0.2 years (range, 2 d-3.5 yr) were studied. Operative level was C4-C5 in 20% (6 of 30), C5-C6 in 47% (14 of 30), C6-C7 in 20% (6 of 30), and unknown in 13% (4 of 30). Polyethylene and metallic (cobalt chrome molybdenum [CoCrMo]) components were examined using light stereo-microscopy (6X-31X), scanning electron microscopy, and energy dispersive x-ray analysis. CTDRs were explanted for indications of axial pain (n = 9), radicular symptoms (n = 6), atraumatic loosening (n = 6), trauma (n = 5), metal allergy (n = 1), myelopathy (n = 1), hypermobility (n = 1), and unknown (n = 1). Surface area of ongrowth (mean = 7.2 ± 1.4%) was not associated with operative level (P = 0.37), surgeon-reported axial pain (P = 0.56), or atraumatic loosening (P = 0.93). Burnishing consistent with metallic endplate impingement was present in 80% (24 of 30) of retrieved CTDRs, most commonly in the posterior quadrant (P < 0.001). There was no association between implant height (P = 0.19) or depth (P = 0.17) and posterior impingement. Backside wear was not observed on any of the disassembled implants (0 of 16). Third-body wear occurred in 23% (7 of 30) and the donor site was confirmed by scanning electron microscope/energy dispersive x-ray analysis to be the porous-coated surface of the CTDR. Early clinical failures of Prodisc-C CTDRs display surface damage evidence of metal endplate-endplate impingement, most commonly posteriorly. Backside wear was not evident; however, third-body wear was found. Future studies will determine the clinical impact of these predominant modes of wear on long-term metal-on-polyethylene semiconstrained CTDR performance.