Accumulation Of Wear Particles Research Articles

Attachment of cartilage wear particles to the synovium negatively impacts friction properties

Cartilage wear particles are released into the synovial fluid by mechanical and chemical degradation of the articular surfaces during osteoarthritis and attach to the synovial membrane. Accumulation of wear particles could alter key tissue-level mechanical properties of the synovium, hindering its characteristically low-friction interactions with underlying articular surfaces in the synovial joint. The present study employs a custom loading device to further the characterization of native synovium friction properties, while investigating the hypothesis that attachment of cartilage wear particles increases friction coefficient. Juvenile bovine synovium demonstrated characteristically low friction coefficients in sliding contact with glass, in agreement with historical measurements. Friction coefficient increased with higher normal load in saline, while lubrication with native synovial fluid maintained low friction coefficients at higher loads. Cartilage wear particles generated from juvenile bovine cartilage attached directly to synovium explants in static culture, with incorporation onto the tissue denoted by cell migration onto the particle surface. In dilute synovial fluid mimicking the decreased lubricating properties during osteoarthritis, wear particle attachment significantly increased friction coefficient against glass, and native cartilage and synovium. In addition to providing a novel characterization of synovial joint tribology this work highlights a potential mechanism for cartilage wear particles to perpetuate the degradative environment of osteoarthritis by modulating tissue-level properties of the synovium that could impact macroscopic wear as well as mechanical stimuli transmitted to resident cells.

Defect-related luminescent bur-like hydroxyapatite microspheres induced apoptosis of MC3T3-E1 cells by lysosomal and mitochondrial pathways.

When orthopedic joints coated by hydroxyapatite (HA) were implanted in the human body, they release wear debris into the surrounding tissues. The generation and accumulation of wear particles will induce aseptic loosening. However, the potential bioeffect and mechanism of HA-coated orthopedic implants on bone cells are poorly understood. In this study, defect-related luminescent bur-like hydroxyapatite (BHA) microspheres with the average diameter of 7-9 μm which are comparable to that of the wear-debris particles from aseptically loosened HA implants or HA debris have been synthesized by hydrothermal synthesis and the MC3T3-E1 cells were set as a cells model to study the potential bioeffect and mechanism of BHA microspheres. The studies demonstrated that BHA microspheres could be taken into MC3T3-E1 cells via endocytosis involved in micropinocytosis- and clathrin-mediated endocytosis process, and exert cytotoxicity effect. BHA microspheres could induce the cell apoptosis by intracellular production of reactive oxygen species (ROS), which led to not only an increase in the permeability of lysosome and release of cathepsins B, but also mitochondrial dysfunction and DNA damage. Our results provide novel evidence to elucidate their toxicity mechanisms and might be helpful for more reasonable applications of HA-based orthopaedic implants in the future.

Aggravation of inflammatory response by costimulation with titanium particles and mechanical perturbations in osteoblast- and macrophage-like cells

The interface between bone tissue and metal implants undergoes various types of mechanical loading, such as strain, compression, fluid pressure, and shear stress, from daily activities. Such mechanical perturbations create suboptimal environments at the host bone-implant junction, causing an accumulation of wear particles and debilitating osseous integration, potentially leading to implant failure. While many studies have focused on the effect of particles on macrophages or osteoprogenitor cells, differential and combined effects of mechanical perturbations and particles on such cell types have not been extensively studied. In this study, macrophages and osteoprogenitor cells were subjected to physiological and superphysiological mechanical stimuli in the presence and absence of Ti particles with the aim of simulating various microenvironments of the host bone-implant junction. Macrophages and osteoprogenitor cells were capable of engulfing Ti particles through actin remodeling and also exhibited changes in mRNA levels of proinflammatory cytokines under certain conditions. In osteoprogenitor cells, superphysiological strain increased proinflammatory gene expression; in macrophages, such mechanical perturbations did not affect gene expression. We confirmed that this phenomenon in osteoprogenitor cells occurred via activation of the ERK1/2 signaling pathway as a result of damage to the cytoplasmic membrane. Furthermore, AZD6244, a clinically relevant inhibitor of the ERK1/2 pathway, mitigated particle-induced inflammatory gene expression in osteoprogenitor cells and macrophages. This study provides evidence of more inflammatory responses under mechanical strains in osteoprogenitor cells than macrophages. Phagocytosis of particles and mechanical perturbation costimulate the ERK1/2 pathway, leading to expression of proinflammatory genes.

Evaluation of silicon nitride as a wear resistant and resorbable alternative for total hip joint replacement

Many of the failures of total joint replacements are related to tribology, i.e., wear of the cup, head and liner. Accumulation of wear particles at the implants can be linked to osteolysis which leads to bone loss and in the end aseptic implant loosening. Therefore it is highly desirable to reduce the generation of wear particles from the implant surfaces. Silicon nitride (Si3N4) has shown to be biocompatible and have a low wear rate when sliding against itself and is therefore a good candidate as a hip joint material. Furthermore, wear particles of Si3N4 are predicted to slowly dissolve in polar liquids and they therefore have the potential to be resorbed in vivo, potentially reducing the risk for aseptic loosening. In this study, it was shown that α-Si3N4-powder dissolves in PBS. Adsorption of blood plasma indicated a good acceptance of Si3N4 in the body with relatively low immune response. Si3N4 sliding against Si3N4 showed low wear rates both in bovine serum and PBS compared with the other tested wear couples. Tribofilms were built up on the Si3N4 surfaces both in PBS and in bovine serum, controlling the friction and wear characteristics.

Histological and morphometric studies of femurs with stable hip joint replacement. An autopsy study with special reference to factors leading to late loosening

To gain insight into the tissue reactions leading to non-infectious loosening 25 autopsy specimens of femurs with well-fixed cemented femoral components of hip prostheses were analysed histomorphologically and morphometrically. The implant duration ranged from one month to 15 years. With the exception of some focal bone-cement contacts bone and cement were separated by a fibrohistiocytic soft tissue membrane. This membrane contained wear particles predominantly of the bone cement mantle and--less abundant--of the polyethylene cups. The amount of wear particles as well as histiocytes and necroses within the membrane statistically significantly increased with advancing time in situ. The cancellous bone adjacent to the soft tissue membrane often revealed a mainly histiocytic infiltration too, accompanied by bone remodeling in this area. The histiocytic inflammatory reaction at the bone cement interface, which is mainly caused by the accumulation of wear particles is considered to be of major importance for the non infectious late loosening of cemented prostheses.

Absence of lymphatics at the bone-implant interface: Implications for periprosthetic osteolysis

Background Wear particles, found at the bone-implant interface surrounding a loose prosthesis, are commonly phagocytosed by macrophages. Wear particles and wear particle-containing macrophages are also found in regional lymph nodes draining arthroplasty tissues. The means by which wear particles are transported from arthroplasty tissues to lymph nodes is uncertain, as the presence or absence of lymphatic vessels in periprosthetic tissues has not been established.Methods We determined immunophenotypic expression of LYVE-1 and podoplanin, two highly specific lymphatic endothelial cell markers, in the hip arthroplasty pseudocapsule surrounding the false joint and the bone-implant interface of the femoral and acetabular pseu-domembrane.Results LYVE-1+/podoplanin+ lymphatic vessels were not identified in the pseudomembrane but were found in the pseudocapsule. Normal bone did not contain lymphatic vessels.Interpretation Our findings suggest that the wear particles shed at the bone-implant interface are not transported to draining lymph nodes by lymphatics directly from the pseudomembrane, but via the pseudocapsule. The absence of a lymphatic clearance mechanism may contribute to accumulation of wear particles at the bone-implant interface and promote periprosthetic osteolysis through stimulation of osteoclast formation and activity.

Comparative Histological and Morphometric Autopsy Study of Femora and Acetabula with Stable Cemented Hip Prostheses

To gain insight into the tissue reactions leading to non-infectious prosthesis loosening autopsy specimens of 9 stable cemented femoral and acetabular components 1 to 16 years in situ were analysed histomorphologically and morphometrically. In femora and acetabula, bone and cement were separated by an interface membrane composed of connective tissue and granulation tissue after short implant duration. After longer implant duration, infiltrates of macrophages containing wear particles of the bone cement and – though less abundant – polyethylene predominated. The interface membranes of the acetabula appeared three times as broad as in proximal parts of the femora. They showed no topographical variations. In the femora, however, the membranes were proximally considerably thicker than in distal parts. In both femora and acetabula, the adjacent spongiosa were infiltrated by macrophages as well. The cancellous bone showed remodelling with formation of a neocortical layer at the border between the spongiosa and the interface membrane. Focal metaplastic formation of cartilage was also present. The results indicate that in femora and acetabula, basically analogous mechanisms lead to non-infectious late loosening, which is connected with the accumulation of wear particles and macrophages in the interface membrane. A positive correlation of the width of the interface membrane with the implant duration was found only in the acetabulum. This could explain the comparatively frequent socket loosening.

Fractal characterization of wear particle accumulation in the wear process

To find a more accurate method characterizing wear particles, fractal geometry is applied in this paper describing wear particle accumulation. The wear experiments are carried out on a pin-on-disc test rig under dry friction conditions for a copper alloy pin and a steel disk. The results demonstrate that the logarithm of wear particle accumulation shows good linearity with the logarithm of the measured particle size. The relation between the accumulation of wear particles and the particle size presents a strong bi-fractal behavior. In addition, it is discovered that the fractal dimension of wear particle accumulation changes in different wear stages. The changes of the transition points of the bi-fractals correspond to the wear state variations.

Wear of metals in a magnetic field

The effect of a normal magnetic field on the wear of Cu/Fe and Zn/Fe systems has been investigated in atmospheres of air and Ar. In Cu-Fe rubbing in air, a severe-mild wear transition is accelerated and the mild wear rate is increased by the magnetic field. In Zn-Fe rubbing in air, mild wear is also increased. In Ar atmospheres, however, the magnetic field does not have any effect. These magnetic effects are thought to be due to the activity of O 2 chemisorption onto the metals being enhanced by the magnetic field. Especially in the severe wear region, accumulation of wear particles by the magnetic field operates effectively, which is also thought to be a cause of the acceleration of the severe-mild wear transition.

Tissue response in relation to type of wear particles around failed hip arthroplasties

To establish the types of wear particles and associated tissue response around human prostheses the periprosthetic tissues around 50 hip arthroplasties revised for aseptic loosening of one or more components were examined by light microscopy, transmission electron microscopy, and energy-dispersing x-ray microanalysis. The tissues around cementless metal-on-bone and ceramicon-ceramic prostheses contained few or no prosthesis wear particles. The tissues around metal-on-metal prostheses contained large numbers of metal particles and large numbers of macrophages, and occasional multinucleate giant cells. The tissues around cemented metal-on-polyethylene prostheses often contained large numbers of small and large polyethylene particles, variable numbers of cement particles, and occasional metal particles. Large numbers of macrophages and multinucleate giant cells were frequently seen in these tissues. Lymphocytes were occasionally seen in association with metal particles. Ultrastructural studies of the periprosthetic tissues confirmed the phagocytosis of submicroscopic wear particles by macrophages. Varying degrees of degenerative change in macrophages were seen in association with phagocytosis of metal particles. Large numbers of cytolysosomes were seen in cells in association with the accumulation of wear particles.