Surfaces Of Artificial Joints Research Articles

삼차원 인공 절리면의 생성과 이에 대한 거칠기 특성 평가

삼차원 인공 절리면의 생성과 이에 대한 거칠기 특성 평가

Biological responses of diamond-like carbon (DLC) films with different structures in biomedical application

Diamond-like carbon (DLC) films are potential candidates for artificial joint surface modification in biomedical applications, and the influence of the structural features of DLC surfaces on cell functions has attracted attention in recent decades. Here, the biocompatibility of DLC films with different structures was investigated using macrophages, osteoblasts and fibroblasts. The results showed that DLC films with a low ratio of sp2/sp3, which tend to have a structure similar to that of diamond, led to less inflammatory, excellent osteogenic and fibroblastic reactions, with higher cell viability, better morphology, lower release of TNF-α (tumor necrosis factor-α) and IL-6 (interleukin-6), and higher release of IL-10 (interleukin-10). The results also demonstrated that the high-density diamond structure (low ratio of sp2/sp3) of DLC films is beneficial for cell adhesion and growth because of better protein adsorption without electrostatic repulsion. These findings provide valuable insights into the mechanisms underlying inhibition of an inflammatory response and the promotion of osteoblastogenesis and fibrous propagation, and effectively build a system for evaluating the biocompatibility of DLC films.

Curved surface turbulence precision machining method for artificial joint complex of titanium alloy

Titanium alloy is widely used in the design of artificial joints because of its high strength and low modulus. But, titanium alloy has its defects such as poor machinability, low thermal conductivity. The surface of artificial joints is usually complex curved surface, which makes that high surface quality cannot be easily obtained by using conventional processing methods. Aiming at the processing problems for the complex surface of titanium alloy artificial joints, a partial coverage constraint style complex surface turbulence precision machining method is proposed for titanium alloy artificial joint. The partial covering surface binding component is established by profiling of the artificial joint surface, so the controlled flow channel of abrasive flow is built. The processing surface is a part of the flow channel wall, which making abrasive flow into the turbulent fully developed state. The micro-cutting of the processing surface is realised by the disorderly movement of the abrasive to reach the mirror-level surface roughness. The experiment results show the effectiveness and feasibility of this method.

Textured bearing surface in artificial joints to reduce macrophage activation

Micro slurry-jet erosion has been proposed as a precision machining technique for the bearing surfaces of artificial joints in order to reduce the total amount of polyethylene wear and to enlarge the size of the wear debris. The micro slurry-jet erosion method is a wet blasting technique which uses alumina particles as the abrasive medium along with compressed air and water to create an ideal surface. Pin-on-disc wear tests with multidirectional sliding motion on the textured surface of a alloy counterface for polyethylene resulted in both a reduction of wear as well as enlargement of the polyethylene debris size. In this study, primary human peripheral blood mononuclear phagocytes were incubated with the debris, and it was elucidated that the wear debris generated on the textured surface regulated secretion of the proinflammatory cytokines IL-6 and TNF-α, indicating a reduction in the induced tissue reaction and joint loosening.

Surface Modifications for Improved Wear Performance in Artificial Joints: A Review

Artificial joint replacement is one of the most successful treatments for arthritis. Excellent wear and corrosion resistance, together with high strength and fracture toughness, are fundamental requirements for implant materials. Wear and/or corrosion of the materials used in artificial joints may lead to implant failure. Therefore, hard and wear-resistant materials, like cobalt-chromium-molybdenum and ceramic, are currently used as bearing surfaces. However, even using such hard materials, wear and/or corrosion related failure of artificial joints remains a central concern. One primary goal in orthopedic biomaterials research is to create more wear-resistant surfaces. Different technologies have been used to create new surfaces, or to modify existing surfaces, to prevent wear. It is the intent of this overview first to provide a summary of materials currently used as bearing surfaces in artificial joints, their functions, and their contributions to device longevity. Then, we will discuss advancements in modifying those bearing surfaces to produce more wear-resistant artificial joints.

Characterization of Anisotropy of Joint Surface Roughness and Aperture by Variogram Approach Based on Digital Image Processing Technique

The mechanical and hydraulic anisotropy of rock joints are strongly dependent on the surface roughness and aperture. To date, accurate quantification of the anisotropic characteristics of joint surfaces remains a key issue. For this purpose, the digital image processing (DIP) technique was used to retrieve the joint surface topography, and a variogram function was used to characterize the anisotropy of the joint surface roughness and estimate the joint aperture. A new index, SRV, related to both the sill and the range of the variogram is proposed to describe the anisotropy of the joint surface roughness, and a new aperture index, b, is derived to quantify the joint aperture. These newly proposed indexes, SRV and b, were validated by characterizing three artificial triangular joint surfaces, then the values of both SRV and b were calculated along 42 directions on an artificial joint surface. The range of SRV was between 0.058622 and 0.331283, while that of b was from 0.270433 to 0.397715 mm. The results show that the newly proposed indexes SRV and b are effective for quantifying the anisotropic roughness and aperture of joint surfaces, respectively. In addition, based on the hypothesis that there exists a smooth upper wall for the artificial joint, a relationship between the indexes SRV and b was obtained based on the data analysis. It indicates that the trends of the indexes SRV and b tend to coincide, although some of their individual values differ. In this respect, the hydraulic aperture of rock joints is related to not only surface roughness but also the distribution of asperities on the surface. In addition, this method can also be used to characterize the roughness of real rock joints when the joint surface is treated by dying with ink before taking digital photos. This study provides a new method for properly quantifying the directional variability of joint surface roughness and estimating the mechanical and hydraulic properties of rock joints based on the DIP technique.

Observation of the Degradation Characteristics and Scale of Unevenness on Three-dimensional Artificial Rock Joint Surfaces Subjected to Shear

The present study explores the degradation characteristics and scale of unevenness (small-scale roughness) on sheared rock joint surfaces at a low-stress regime. While the degradation characteristics of unevenness and the normal stress are mutually interrelated, an understanding of the degradation patterns of the three-dimensional roughness of rock joints is one of the important components needed to identify asperity failure characteristics and to quantify the role of damaged unevenness in establishing a shear strength model. A series of direct shear tests was performed on three-dimensional artificial rock joint surfaces at different normal stress levels. After shearing, the spatial distributions and statistical parameters of degraded roughness were analysed for the different normal stress levels. The length and area of the degraded zones showed bell-shaped distributions in a logarithmic scale, and the dominant scale (or the most frequently occurring scale) of the damaged asperities (i.e., unevenness) ranged from approximately, 0.5 to 5.0 mm in length and 0.1–10 mm2 in area. This scale of the damaged unevenness was consistent regardless of the level of normal stress. It was also found that the relative area of damaged unevenness on a given joint area, and thus the contribution of the mechanical asperity failure component to shear strength increased as normal stress increased.

Investigation of the Shear Stress Relaxation Characteristics of a Structural Plane Using the Isostress Cyclic Loading Method

In this study, the isostress cyclic loading method (ICLM) was proposed to study the shear stress relaxation characteristics of rock with a structural plane and the connection between the stress relaxation and long-term strength. Samples with artificial joint surfaces based on the 4th, 6th, and 10th discontinuity lines from Barton’s ten standard lines were poured using cement mortar. Shear stress relaxation tests were conducted with a biaxial rheological testing machine using the ICLM under various stress levels, where the shearing loading value was larger than the long-term strength. The law of shear stress relaxation was studied based on the test results. The interaction mechanism between stress relaxation and creep was discussed, and a stress relaxation method was proposed to determine the long-term strength that achieved the optimal results. This study could provide a reference for engineering practices and preparation for constitutive studies.

J0250102 人工関節軸受部の表面テクスチャが生体反応因子に与える影響

Micro slurry-jet erosion has been proposed as a precision machining technique for the bearing surfaces of artificial joints in order to reduce the total amount of polyethylene wear and to enlarge the size of the wear debris. The micro slurry-jet erosion method is a wet blasting technique which uses alumina particles as an abrasive medium along with compressed air and water to create an ideal surface. From pin-on-disc wear tests with multidirectional sliding motions, the textured surface on a Co-Cr-Mo alloy could change the total amount of wear of polyethylene.

The stability of DLC film on nitrided CoCrMo alloy in phosphate buffer solution

Abstract CoCrMo alloy is often used as the material for metal artificial joint, but metal debris and metal ions are the main concern on tissue inflammation or tissue proliferation for metal prosthesis. In this paper, nitrogen ion implantation and diamond like carbon (DLC) film composite treatment was used to reduce the wear and ion release of biomedical CoCrMo substrate. The mechanical properties and stability of N-implanted/DLC composite layer in phosphate buffer solution (PBS) was evaluated to explore the full potential of N-implanted/DLC composite layer as an artificial joint surface modification material. The results showed that the DLC film on N implanted CoCrMo (N-implanted/DLC composite layer) had the higher surface hardness and wear resistance than the DLC film on virgin CoCrMo alloy, which was resulted from the strengthen effect of the N implanted layer on CoCrMo alloy. After 30 days immersion in PBS, the structure of DLC film on virgin CoCrMo or on N implanted CoCrMo had no visible change. But the adhesion and corrosion resistance of DLC on N implanted CoCrMo (N-implanted/DLC composite layer) was weakened due to the dissolution of the N implanted layer after 30 days immersion in PBS. The adhesion reduction of N-implanted/DLC composite layer was adverse for in vivo application in long term. So researcher should be cautious to use N implanted layer as an inter-layer for increasing CoCrMo alloy load carrying capacity in vivo environment.

Modelling and optimization of biotribological testing parameters on frictional heating of vitamin E blended UHMWPE with the help of statistical techniques

It is known from previous studies that frictional temperature rise on the surfaces of artificial joints could reach high levels that make hazardous effects on surrounding tissue and lubricant around the artificial joint. For enhancement the tribological behavior of the joints, new material combinations have been tried. In this study vitamin E blended ultra-high molecular weight polyethylene (VE-UHMWPE), which is one of the new generation material, was used for acetabular inserts. These inserts were paired with CoCrMo femoral heads. For reduction of the frictional heating, testing parameters and their effects were investigated by using Taguchi method and analysis of variance. The results were analyzed by using Statistical Package for Social Science (SPSS 15.0). Also mathematical model for the temperature rise (ΔT) was developed with the help of statistical techniques.In vitro frictional heating measurements were carried out on a custom made hip joint friction experimental set-up. 0.3–0.5mm in diameter surface dimples were machined on the inner surface of acetabular insert samples. Different static loads, representing different body weights, were applied with different walking duration. Bovine calf serum was used as lubricant and different amount of bone cement (PMMA) was added in the lubricant as third body abrasive particles. Temperature rises were recorded with embedded thermocouples. The experimental results demonstrated that the surface dimples were the major factor on frictional heating, followed by applied load, amount of third body particles and time.

Measurement and theoretical determination of frictional temperature rise between sliding surfaces of artificial hip joints

Frictional heating of articulating surfaces may influence the rate of wear, fatigue, creep and oxidative degradation of bearing materials. Also temperature rise can damage the surrounding tissue and lubricant around the artificial joint and contributes insert loosening. The objective of this study is to determine temperature rise between sliding surface of vitamin E blended UHMWPE and conventional UHMWPE acetabular component paired with a cobalt–chromium–molybdenum (CoCrMo) femoral component, as a function of sliding time and applied load. Besides the experimental studies, the frictional temperature rise of conventional UHMWPE was theoretically calculated. Frictional measurements of the joints were carried out on a custom made hip joint friction simulator. The diameter of the prostheses was 28mm. Applied static loads were changed from 200N to 1500N. In flexion–extension plane, a simple harmonic oscillatory motion between ±24° was applied to the UHMWPE acetabular component. The period of motion was 1Hz and the tests were run up to 11,000 cycles. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. Both the experimental temperature rise values and theoretical calculations results were compared and evaluated.

Numerical lubrication simulation of metal-on-metal artificial hip joint replacements: Ball-in-socket model and ball-on-plane model

Long-term successful function of artificial hip joint replacements strongly depends on the design parameters of the bearing such as the diameters of femoral head and acetabular cup and the corresponding radial clearance, which determine the lubrication regime experienced in the prostheses. Generally, there are two types of numerical models for elastohydrodynamic lubrication (EHL) analysis of the bearing in the hip joint replacements: ball-in-socket model and effective ball-on-plane model. As the real hip joint is in ball-in-socket configuration, the ball-in-socket lubrication model should be the reasonable approximation to the real bearing. The ball-in-socket model solves a lubrication problem in spherical coordinates, which means all of governing equations, including Reynolds equation, film thickness and load balance equation, should be written in the spherical coordinate forms. In addition, the calculation of the elastic deformation of the bearing surfaces in artificial joints is not a trial problem. Complex spherical geometries in the joint bearing often require employing the finite-element method to determine/extract the displacement influence coefficients at first, and then the deformation is evaluated through using an equivalent discrete spherical convolution model. Fortunately, the fast Fourier transform-based approach is recently developed to speed up the deformation calculation. In comparison with the ball-in-socket model, the effective ball-on-plane model is simple and easy to conduct EHL analysis. The main characteristic of the effective ball-on-plane model is that the elastic deformation was evaluated under an assumption of semi-infinite solid and certainly without the consideration of the curvature effect associated with the ball-in-socket configuration. In the present study, some typical cases of EHL analysis for hip joint replacements were conducted to systematically demonstrate the capability of these two models. It was found that both models were able to provide quite close results in most situations, and the difference may only take place when the head is positioned near the edge of the cup bearing surface.

Wear studies on the likely performance of CFR-PEEK/CoCrMo for use as artificial joint bearing materials

It is well known that a reduction in the volume of wear produced by articulating surfaces in artificial joints is likely to result in a lower incidence of failure due to wear particle induced osteolysis. Therefore, new materials have been introduced in an effort to produce bearing surfaces with lower, more biologically acceptable wear. Polyetheretherketone (PEEK-OPTIMA) has been successfully used in a number of implant applications due to its combination of mechanical strength and biocompatibility. Pin-on-plate wear tests were performed on various combinations of PEEK-OPTIMA and carbon fibre reinforced PEEK-OPTIMA (CFR-PEEK) against various CoCrMo alloys to assess the potential of this material combination for use in orthopaedic implants. The PEEK/low carbon CoCrMo produced the highest wear. CFR-PEEK against high carbon or low carbon CoCrMo provided low wear factors. Pin-on-plate tests performed on ultra-high molecular weight polyethylene (UHMWPE) against CoCrMo (using comparable test conditions) have shown similar or higher wear than that found for CFR-PEEK/CoCrMo. This study gives confidence in the likelihood of this material combination performing well in orthopaedic applications.

Potential of wear resistant coatings on Ti–6Al–4V for artificial hip joint bearing surfaces

Tribological screening tests (simple, reciprocating ball-on-flat tests) were performed with the objective to identify an appropriate coating for the articulating surfaces of artificial hip joints whose acetabular cups and femoral stems are made from Ti–6Al–4V alloy, which is appreciated for its light weight, good biocompatibility and elastic properties similar to those of natural bone. Standard coatings like TiN or CrN performed better than more complicated multi-layer systems, though not as good as different types of amorphous carbon coatings, generally referred to as diamond-like carbon or DLC coatings. Among the latter, hydrogenated amorphous carbon (a-C:H) displayed the best properties, especially if the hydrogen content was increased by reducing the bias voltage during PA-CVD-deposition. The optimised a-C:H coating revealed the most promising wear behaviour under the applied testing conditions, i.e. the increase of linear wear with the number of cycles was close to zero. Regarding the materials examined in this study, correlation of wear with mechanical properties obtained by nano-indentation revealed that high hardness was not an adequate criterion for selecting appropriate coatings. A high ratio of hardness and elastic modulus (H/E) proved to be more important. Microstructural and micro-analytical investigations revealed transformation of TiN and CrN to TiO 2 and Cr 2O 3, respectively, and amorphous carbon was, at least partly, transformed to graphite. Furthermore, incorporation of Al 2O 3 from the ball was observed at a very fine scale. The wear debris of favourable coatings always formed agglomerates of nano-scale particles. It was shown that commercial nano-particles of Al 2O 3, Cr 2O 3 and carbon black are comparable to particles generated by the tribological tests. However, it is uncertain whether they are comparable to those formed during simulator studies or in vivo. Furthermore, the performance of the favourable coating has to be tested in a hip joint simulator before its potential for application in prostheses can be assessed.

Stress microscopy and confocal Raman imaging of load-bearing surfaces in artificial hip joints

Confocal Raman microprobe spectroscopy is a technique with considerable potential in biomedical science owing to its ability to nondestructively scan samples in 3D with high spatial resolution and to precisely characterize the chemical, physical and mechanical characteristics of biomaterials at their molecular scale. Beyond the capacity of other conventional assessments of biomaterial oxidation state, crystalline and phase fractions, Raman and luminescence techniques can be used for assessing residual stress fields in artificial hip joints. Provided that the probe response function characterizing the probe/biomaterial interaction is known, 3D residual stress fields can be determined precisely with high axial and lateral resolution.

パラメトリック多項式による人工膝関節曲面形状の復元と曲率解析(S01-2 身体機能のモデリングと福祉工学(2),S01 身体機能のモデリングと福祉工学)

Curvature analyses on the artificial knee joint surfaces have not been fully performed. In this study, artificial knee joint surfaces were described by the parametric polynomials in order to suppress unnecessary undulation which might be generated during the reconstruction processes when other equations were applied. Then, curvature analyses were performed or three types of artificial knee joints which have been described by the above-mentioned polynomials. Further, congruencies between the femoral condyles and the insertion plate fixed on the tibia were introduced at various knee angles. Finally, the features of the surface shapes were discussed for three types of artificial knee joints.

Study on Mathematical Description of Human Knee Joint Surface and Its Application

For describing free-formed surfaces mathematically, parameterized polynomial function was proposed in our previous study. By using our parameterized polynomial, the artificial knee joint surfaces were described in detail and the results were found to be superior to the established practices. However, this polynomial function has some problem for reconstructing human knee joint surface with minute undulation. In the present study, to overcome this problem, an additional application of Fourier series approximation was employed. First, the global shape of objective surface was described by our polynomial function. Then, minute undulation was approximated with Fourier series function. Finally, two sets of approximated surface were superimposed to reproduce the original surface in a complete fashion. Our newly proposed method was applied to the swine knee joint and human knee joint model surfaces. Curvature analysis was performed for two surfaces.

Optically interferometric roughness measurements for spherical surfaces by processing two microscopic interferograms

This paper discusses a method to carry out optical interferometric measurements for the surface roughness of spheres in a biomedical application to an artificial joint, using two beams of a Michelson interferometric microscope with digital image processing and a computational system. There will be two kinds of microscopic interferograms formed from the interference between the measurement beams reflected from the artificial joint surface and the reference beams from the reference surface. One interferogram has equal circular interference fringes and another has localized arc interference fringes. To process these two interferograms by using a digital image processing system, the edges of each of the interference fringes which are modulated by the micro-structure of the artificial joint surface can be extracted. The paper proposes an algorithm for the calculation of the standard reference mean circles and mean curves from each of the fringe edges by using the least square fitting method and to obtain the profile departures from the reference mean circles and mean curves and the surface roughness parameters.

Application of Parametrized Polynomials for Describing Free-Formed Surfaces.

Although such functions as Bezier, B-Spline and NURBS are widely used in Computer Graphics for generating any freeformed surfaces, they are not necessarily appropriate for describing the existing surfaces; They need structured data sets according to a grid. Their mathematical structures make it almost impossible to obtain entirely smooth surface. To overcome these problems, an application of parametrized polynomial functions was proposed in this study. By using our parametrized polynomial, the artificial knee joint surface was described mathematically and the results were fully compared with those from B-Spline with respect to accuracy and smoothness. Computer generated images were made to demonstrate that our parametrized polynomial was superior to the B-Spline.