Wear Debris Particles Research Articles

Analysis of 118 second-generation metal-on-metal retrieved hip implants

Osteolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants. Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 μm for the whole articulation per year in the first year, decreasing to about 5 μm per year after the third. Metal surfaces have a ‘self-polishing’ capacity. Scratches are worn out by further joint movement. Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis.

Structural studies of wear debris from carbon–carbon composite aircraft brakes

Microstructural studies using X-ray diffraction, SEM, and optical microscopy were made of wear debris from carbon–carbon composite aircraft brakes produced under different simulated braking operations. Under simulated cold taxiing conditions, particulate wear debris comprising a disordered carbon phase containing fibre fragments is formed. The disordered phase is produced mainly by shear deformation of the graphitic CVI matrix in the parent carbon–carbon composite. Under simulated landing conditions the wear debris is partly transformed by shear processes into a friction film with a similar disordered microstructure to the wear debris formed during taxiing. The friction film is formed as a result of the higher power density and interfacial temperatures during landing. The very high power densities and interface temperatures that apply during rejected take-off result in shear-stress assisted graphitisation of the friction film, but with a fine mosaic texture that is quite different from the texture of the CVI matrix in the parent composite.

Analysis of 118 second-generation metal-on-metal retrieved hip implants.

Osteolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants. Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 microm for the whole articulation per year in the first year, decreasing to about 5 microm per year after the third. Metal surfaces have a 'self-polishing' capacity. Scratches are worn out by further joint movement. Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis.

Ultrahigh molecular weight polyethylene particles have direct effects on proliferation, differentiation, and local factor production of MG63 osteoblast-like cells.

Small particles of ultrahigh molecular weight polyethylene stimulate formation of foreign-body granulomas and bone resorption. Bone formation may also be affected by wear debris. To determine if wear debris directly affects osteoblasts, we characterized a commercial preparation of ultrahigh molecular weight polyethylene (GUR4150) particles and examined their effect on MG63 osteoblast-like cells. In aliquots of the culture medium containing ultrahigh molecular weight polyethylene, 79% of the particles were less than 1 microm in diameter, indicating that the cells were exposed to particles of less than 1 microm. MG63 cell response to the particles was measured by assaying cell number, [3H]thymidine incorporation, alkaline phosphatase specific activity, osteocalcin production, [35S]sulfate incorporation, and production of prostaglandin E2 and transforming growth factor-beta. Cell number and [3H]thymidine incorporation were increased in a dose-dependent manner. Alkaline phosphatase specific activity, a marker of cell differentiation for the cultures, was significantly decreased, but osteocalcin production was not affected. [35S]sulfate incorporation, a measure of extracellular matrix production, was reduced. Prostaglandin E2 release was increased, but transforming growth factor-beta production was decreased in a dose-dependent manner. This shows that ultrahigh molecular weight polyethylene particles affect MG63 proliferation, differentiation, extracellular matrix synthesis, and local factor production. These effects were direct and dose dependent. The findings suggest that ultrahigh molecular weight polyethylene wear debris particles with an average size of approximately 1 microm may inhibit bone formation by inhibiting cell differentiation and reducing transforming growth factor-beta production and matrix synthesis. In addition, increases in prostaglandin E2 production may not only affect osteoblasts by an autocrine pathway but may also stimulate the proliferation and activation of cells in the monocytic lineage. These changes favor decreased bone formation and increased bone resorption as occur in osteolysis.

Origins of friction and wear of the thin metallic layer of metal evaporated magnetic tape

The origins of friction and wear of the thin metallic layer of metal evaporated (ME) magnetic tapes were determined at an asperity level using a modified commercial video cassette recorder (VCR) as a tape transport, magnetometer and tribometer. The VCR was instrumented to measure friction force between the rotary heads and tape, head-to-tape spacing to nanometer vertical resolution, and sub-microsecond duration signal dropouts caused by loose wear debris particles in the head-to-tape contact interface. ME tapes with various surface texture and the same lubricant thickness were studied, as well as tapes with various lubricant thickness and the same surface texture. To measure the very subtle origins of wear, tapes were recorded and then played back only one time, and surface topography was measured with an atomic force microscope to see if the tapes were worn. For fixed asperity size, increased asperity areal density or more numerous asperities reduced the plastic deformation that was observed at low asperity areal densities. Having more asperities increases the load bearing area near the highest point on the tape. This prevents high strain and associated plastic deformation of high asperities. Thus, spreading the load over more asperities reduces plastic deformation, and deformation becomes primarily elastic. Tapes that exhibited plastic deformation had higher friction force than the tape that exhibited elastic deformation. A simple model was developed which suggests that high friction force is not due to the energy required to plastically deform the asperities, but arises from high real area of contact during sliding for the tapes that plastically deform which is consistent with plasticity theory in the presence of a tangential force. Tapes that plastically deform do not exhibit higher signal dropout frequencies, and this implies that plastic deformation is not associated with loose wear debris particle formation. For smooth tapes with high isolated asperities, cohesive material failure of asperities due to shear stress brought on by friction force resulted in loose wear debris generation, high plowing component to friction force and interface instability. A thicker lubricant layer reduced friction force by reducing the shear strength of adhesive contact junctions.

Polyethylene particles of a ‘critical size’ are necessary for the induction of cytokines by macrophages in vitro

Particulate wear debris from total hip prosthetic components can stimulate macrophages to produce mediators of osteolysis which may cause aseptic implant loosening. This study evaluated the in vitro response of murine peritoneal macrophages to polyethylene particles of difinitive size distributions at varying volume doses. Ceridust 3615 polyethylene particles with a mean size of 0.21, 0.49, 4.3 and 7.2 μm and GUR1120 polyethylene resin with a mean size of 88 μm were co-cultured with C3H murine peritoneal macrophages at volume (μm) 3 to cell number ratios of 100 : 1, 10 : 1, 1 : 1 and 0.1 : 1. The secretion of IL-6, IL-1 β and TNF- α was determined by ELISA. Significantly elevated levels of TNF- α and IL-1 β were determined at 100 : 1 ratios when the macrophages were challenged with particles with a mean size of 0.49, 4.3 and 7.2 μm, and at 10 : 1 ratios for particles with a mean size of 0.49 and 4.3 μm. IL-6 production was significantly elevated at 100 : 1 ratios for mean particle sizes of 0.49 and 4.3 μm. Particles outside this range produced considerably less cytokine suggesting that both the size and volume (or number) of polyethylene particles are critical factors in macrophage activation. Therefore particles in the phagocytosable size range of 0.3–10 μm appear to be the most biologically active.

Nitric oxide release by macrophages in response to particulate wear debris.

At the interface between a prosthetic implant and bone, macrophage interaction with particulate wear debris is a key event in the initiation of localized bone resorption, leading to aseptic loosening of the prostheses. Numerous investigators have reported that macrophages release a variety of cytokines and mediators including tumor necrosis factor, interleukin-1, prostaglandin E2, and interleukin-6 when they are stimulated with particulate wear debris. In this study, we have demonstrated that macrophages stimulated with particulate debris are also capable of releasing in copious amounts a key inflammatory chemical, nitric oxide. This release of nitric oxide was dependent upon the period of culture and the type and dosage of the challenging particles. Titanium-alloy particles were the most stimulatory, followed by commercially pure titanium and polymethyl-methacrylate. While the role of nitric oxide in osteolysis is not clearly understood, the literature suggests that it may be a key mediator in inhibiting DNA synthesis, in cell proliferation, and in stimulating PGE2 release. This finding enhances our understanding of the sequence of events occurring at the bone-implant interface during wear debris-mediated osteolysis, and exposes potential avenues to interrupt this sequence.

Nitric oxide release by macrophages in response to particulate wear debris

Nitric oxide release by macrophages in response to particulate wear debris

The effects of cobalt chromium upon macrophages

The purpose of this study was to elucidate the mechanisms by which cobalt chromium particulate wear debris contribute to the aseptic loosening of total joint prostheses. Incubation of macrophages with cobalt chromium led to release of tumor necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2), but did not lead to release of interleukin-1β (IL-1β) or interleukin 6 (IL-6). Exposure of macrophages cocultured with osteoblasts to cobalt chromium also led to significant release of TNF-α and PGE2, but did not lead to significant IL-6 or IL-1β production. The release of PGE2 in the coculture system was greater than that detected when macrophages were exposed to cobalt chromium without the osteoblast contribution. Exposure of radiolabeled calvaria to media from macrophages incubated with cobalt chromium in coculture with osteoblasts led to release of 45Ca. In contrast, exposure of radiolabeled calvaria to media from isolated macrophages incubated with these particles did not result in release of 45Ca. Exposure of macrophages to cobalt chromium was toxic, as reflected by release of the intracellular enzyme lactate dehydrogenase. Macrophages play a role in the initiation of bone resorption at the interface through the phagocytosis of cobalt chromium particles and subsequent release of TNF-α and PGE2. The presence of osteoblasts at the interface may be required for amplification of the inflammatory response and ultimately for bone resorption. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 468–473, 1998.

The effects of cobalt chromium upon macrophages.

The purpose of this study was to elucidate the mechanisms by which cobalt chromium particulate wear debris contribute to the aseptic loosening of total joint prostheses. Incubation of macrophages with cobalt chromium led to release of tumor necrosis factor-alpha (TNF-alpha) and prostaglandin E2 (PGE2), but did not lead to release of interleukin-1 beta (IL-1 beta) or interleukin 6 (IL-6). Exposure of macrophages cocultured with osteoblasts to cobalt chromium also led to significant release of TNF-alpha and PGE2, but did not lead to significant IL-6 or IL-1 beta production. The release of PGE2 in the coculture system was greater than that detected when macrophages were exposed to cobalt chromium without the osteoblast contribution. Exposure of radiolabeled calvaria to media from macrophages incubated with cobalt chromium in coculture with osteoblasts led to release of 45Ca. In contrast, exposure of radiolabeled calvaria to media from isolated macrophages incubated with these particles did not result in release of 45Ca. Exposure of macrophages to cobalt chromium was toxic, as reflected by release of the intracellular enzyme lactate dehydrogenase. Macrophages play a role in the initiation of bone resorption at the interface through the phagocytosis of cobalt chromium particles and subsequent release of TNF-alpha and PGE2. The presence of osteoblasts at the interface may be required for amplification of the inflammatory response and ultimately for bone resorption.

Plastic Deformation in the Sliding Wear Surfaces of Alumina at Various Temperatures

In order to investigate the sliding wear of alumina, direct observations by TEM and X-ray diffraction line broadening techniques are applied to the wear surfaces and debris particles after the sliding wear tests. of alumina from room temperature to 600degreesC, below the brittle to ductile transition temperature which occurs at approximately 700degreesC. X-ray diffraction of debris particles collected from the test at room temperature reveals heavy deformation within the particles. However, the TEM observations of the wear surface show only isolated dislocations which are mainly associated with grain boundaries, suggesting that the fracture may occur in a broader region than that undergoing the severe deformation. Lattice strain in debris particles estimated by X-ray diffraction line broadening decreases with an increase of the test temperature probably because recovery occurs in the particles by an annealing effect.

Characterization of Titanium Alloy Particulates to Study the in Vitro Release of Inflammatory Mediators by Human Peripheral Blood Monocytes.

Abstract Particulate wear debris found around joint arthroplasties has been linked to the premature failure of artificial joints. Cytokines and eicosanoids released by macrophages are known mediators of inflammation and osteolysis. Previous in vitro studies of wear debris-mediated inflammation have relied upon poorly characterized particulates and peripheral blood cell fractions of mixed cellular composition. The objective of this study was to utilize titanium particulates that closely match wear debris found around joint arthroplasties and to study their effects on the biosynthesis of inflammatory mediators by isolated monocytes. To mimic wear debris that surrounds artificial joints, titanium alloy particulates (1-3 μm in diameter) were obtained. A submicron fraction of these particulates was isolated by differential sedimentation. The morphology, size and concentration of the resulting population was characterized utilizing scanning electron microscopy. Titanium particulate size was estimated from photomicrographs of calibrated latex microspheres mixed with titanium particles (Figure 1). A known volume of titanium particulates in suspension was applied to a carbon planchette and allowed to dry.

The effect of sliding speed on wear of diamond-like carbon coatings

The effect of sliding speed, wear track diameter and sliding distance on the wear behaviour of a diamond-like carbon (DLC) coating deposited using magnetron sputtering from a carbon target at very high ion current density has been investigated applying experimental design and statistical variance analysis. It has been shown that sliding speed has a highly significant effect on wear rate of the DLC coating. Within the sliding speed range studied (0.048 to 0.45 ms−1). a U-shaped parabolic curve for the relationship between specific wear rate and sliding speed has been observed with a minimum wear rate at a speed of approximately 0.25 ms−1. There is a significant negative effect from the combination of sliding speed and distance on wear rate which indicates the involvement of some time-related processes in wear mechanisms for the DLC coating. A model is presented based on the assumption that the control step in the generation of wear debris particles is the chemically activated debonding at the crack tip due to the presence of some reactive species. A semi-quantitative expression for the relationship between the specific wear rate and sliding speed has been derived. Reasonably good agreement between this expression and experimental results was obtained.

The role of triboparticulates in dry sliding wear

In this paper, wear processes and mechanisms for wear transitions with sliding time and temperature during sliding of a nickel-based alloy, N80A, in oxygen at temperatures to 250°C are discussed. Transitions in wear from high rates to low rates with sliding time were always observed at all the temperatures investigated. The transitions in wear were usually accompanied by transitions in contact resistance between the rubbing surfaces from nearly zero to positive high values. It was found that wear debris particles were heavily involved in the wear processes. The transitions in wear and contact resistance with sliding time mainly resulted from the development of wear-protective layers following the compaction of wear debris particles on the rubbing surfaces. The adhesion of triboparticulates to each other and to the rubbing surfaces played an important role in the rapid decrease in wear rate with sliding time and with increase in temperature. Processes involved in the development of the wear-protective particle layers and mechanisms for the wear transitions have been described on the basis of experimental observations. The importance of triboparticulates in wear and its implications for wear protection are discussed.

Sliding wear response of a zinc-based alloy compared to a copper-based alloy

In the present investigation, an attempt has been made to study the wear response of a zinc-based alloy at different sliding speeds and pressures. The wear behavior of the zinc-based alloy has been compared to that of a conventionally used copper-based alloy against an EN24 steel disc. Operative wear mechanisms have also been discussed through the examination of wear surfaces, subsurface regions, and debris particles.

THE PATHOGENESIS OF BONE LOSS FOLLOWING TOTAL KNEE ARTHROPLASTY

Bone loss following total knee arthroplasty (TKA) may be focal or diffuse. It may be caused mechanically, either by unloading of the bone leading to disuse osteoporosis, or by overloading of the bone leading to trabecular fractures and bone destruction. Osteolysis, instigated by an inflammatory reaction to particulate wear debris, is an important and common cause of bone loss after TKA. Less common, though sometimes dramatic, causes of bone loss are infection and osteonecrosis.

Large strains associated with sliding contact of metals

Dislocation studies, especially at large strains, are important for understanding materials aspects of tribological processes. Metallographic evidence shows that sliding causes very large plastic strains and strain gradients adjacent to the interface between the interacting materials. Dislocation densities increase, perhaps achieving saturation values. The resulting micro- structures, including LEDS, are typical of those produced by other ways of producing large strains. Friction can be related to the dissipative processes associated with plastic deformation. Also, the material near the surface becomes unstable to local shear, allowing transfer of pieces of deformed material to the counterface. The transfer material is further deformed and mixed with the counterface material and/or environmental components to produce very fine grained structures, often in the nanocrystal range. Loose wear debris particles are commonly derived from this mixed material, not directly from the base material.

Sliding Wear Response of a Leaded-Tin Bronze: Influence of the Counterface Material Characteristics

Observations were made of the dry sliding wear behavior of a leaded-tin bronze against different counterface materials (stainless, EN8, and EN24 steels) over a range of applied pressures and speeds. The study showed that, in addition to sliding speed and pressure, the characteristics of the counterface materials greatly control the wear response of the bronze. The results were further substantiated by the characteristics of the wear surfaces, subsurface regions, and debris particles generated during the tests.

The Biology of Corrosion and Wear Debris from Orthopedic Implants

AbstractBone loss (osteolysis) following total joint arthroplasty has been a subject of increasing concern in the orthopedic research community. Depending on the distribution and severity, bone loss can lead to aseptic loosening, periprosthetic fracture and formidable reconstructive problems at revision surgery. Bone loss is believed to be primarily a response to particulate wear and corrosion debris derived from the prosthetic materials. Phagocytosed particulates activate macrophages and osteoblasts (and perhaps fibroblasts) to produce factors which stimulate osteoclastic bone resorption and reduce osteoblastic bone formation. To investigate the responses of these cells to particulate corrosion and wear debris, in vitro studies have been performed by measuring factors at both the molecular and cellular levels that may trigger, maintain and/or regulate particulate biomaterial-induced pathologic bone resorption. The biological effect of a particulate species depends upon their size, concentration (number) and composition, in the order listed. Particulate wear debris of phagocytosable size (less that 10 micrometers) activate macrophages, fibroblasts and osteoblasts more effectively that those of larger sizes. As a response to phagocytosed particulates, i) macrophages produce a number of cytokines (interleukins such as II-1, II-6, TNF-alpha) and prostaglandins, which may act either in an autocrine fashion or further stimulate cells present in the periprosthetic tissue; ii) fibroblasts secrete active forms of metalloproteinases; and iii) osteoblasts have diminished collagen type I synthesis. Taken together, particulate corrosion and wear debris provoke a series of biological responses which generate an active microenvironment around prosthetic components. Strategies to modify the host response to particulate degradation products have emerged from these in vitro studies. These strategies may provide pharmacotherapeutic solutions to this important clinical problem.

The respective role of oxygen and water vapor on the tribology of hydrogenated diamond-like carbon coatings

The tribological behavior of diamond-like carbon coatings (DLC) strongly depends on the chemical nature of the test environment. The present study proposes to explore the influence of water vapor and oxygen on the friction behavior of a hydrogenated DLC coating exhibiting ultralow friction in ultrahigh vacuum (friction coefficient below 0.01). Using a UHV tribometer, reciprocating pin-on-flat friction tests were performed in progressively increasing or decreasing partial pressures of pure oxygen and pure water vapor. The maximum gaseous pressures of oxygen and water vapor were 60 hPa and 25 hPa (1 hPa = 100 Pa), respectively, the second value corresponding to a relative humidity (RH) of 100% at room temperature. It was found that, for the pressure range explored, oxygen does not change the ultralow friction behavior of DLC observed in UHV. Conversely, water vapor drastically changes the friction coefficient at pressures above 0.5 hPa (RH = 2%), from about 0.01 to more than 0.1. Electron energy loss spectroscopy and in situ Auger electron spectroscopy have been performed to elucidate the friction mechanisms responsible for the tribological behaviors observed with the two different gaseous environments. In all cases no significant oxidation has been observed either inside the wear scars or in the wear debris particles. Ultralow friction is systematically associated with a homogeneous carbon-based transfer film. The higher friction observed at partial pressure of water vapor higher than 0.5 hPa, is associated with a thinner transfer film. Consequently friction seems to be controlled by the transfer film whose kinetics of formation strongly depends on the partial pressure of water vapor.