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  • 1
    Electronic Resource
    Electronic Resource
    Induction of Interleukin-6 Release in Human Osteoblast-Like Cells Exposed to Titanium Particles In Vitro (2000)
    Springer
    Calcified tissue international 67 (2000), S. 151-155 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Interleukin-6 — MG-63 cells — Titanium particles — Signal transduction — Transcription factor.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Orthopaedic wear debris induces release of bone-resorbing factors from macrophages and fibroblasts. However, the extent to which elemental metallic particles induce bone cells to express factors contributing to implant loosening remains unclear. This study showed that exposure of MG-63 osteoblast-like cells to titanium particles at a concentration of 0.30% v/v resulted in a 15-fold increase in IL-6 release into the culture medium after 24 hours, when compared with cells without particles. Northern blots revealed that exposure of MG-63 cells to titanium particles at a concentration of 0.30% v/v for 24 hours increased IL-6 mRNA signal levels by 9.6-fold, when compared with control cultures. Pretreatment of MG-63 cells with cytochalasin B prevented the particle-induced increase of IL-6 expression but did not alter the basal level of IL-6 release from cells cultured in the absence of particles. The protein kinase C inhibitor, H7, and the serine/threonine kinase inhibitor, genistein, abolished the particle-induced increase in IL-6 release at a concentration of 100 μM for each compound. In contrast, an inhibitor of protein kinase A, HA1004, had no effect on the particle-induced increase in IL-6 release. The transcription factors, nuclear factor IL-6 and nuclear factor kappa B, translocated into the nucleus within 1 hour of particle exposure. This study showed that osteoblast-like cells respond to titanium particles through increased expression of the proinflammatory cytokine, IL-6, in a process requiring phagocytosis and intracellular signaling pathways. These results suggest that osteoblasts play a direct role in implant loosening because of localized release of soluble mediators such as interleukin-6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00223001125
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  • 2
    Electronic Resource
    Electronic Resource
    In vivo and in vitro comparative studies of animal articular surfaces (1975)
    Springer
    Annals of biomedical engineering 3 (1975), S. 100-110 
    Details
    ISSN: 1573-9686
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The contours in the articular surfaces of rabbit and canine knee joints were measured in vivo and in vitro using the scanning electron microscope (SEM), replication, and light-microscopy techniques. Using the light microscope, patterns of highlights of the order 10 μm were observed when the living joint-surfaces were exposed. Replicas were made of these surface contours using Xantopren, a light-bodied dental silicone impression-material. More than 50% of the replicas were discarded because of defects. In the SEM, a crazing phenomenom was sometimes evident on the replicated surfaces which may have been attributable to distortion of the silicone medium, possibly in vacuo. The interpretable replicas from the living joint-surfaces contained 7 to 20 μm diameter humps that varied from 0.5 to 2.5 μm high. These corresponded to the patterns of highlights seen with the light microscope at surgery. Examination of the replicas taken in vitro and direct examination of the cartilage in the SEM revealed comparable data. The living articular-cartilage contours, therefore, appear to correspond to those previously identified in vitro. We emphasize that although these values give some indication of the anticipated in vivo contours, the actual contours in a load-carrying situation may differ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000007
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation and characterization of wear debris of orthopedic materials for biocompatibility studies (1976)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 10 (1976), S. 653-670 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In order to test the biocompatibility of wear debris of orthopedic materials, a method has been developed to produce artificial debris of stainless steel, cobalt-chromium alloy, and high-density polyethylene. In this process, called the accelerated rubbing process, two cylindrical blocks of the same alloy were held under normal pressure in triply distilled water. One block remained stationary while the other rotated at ∼4000 rpm. The water with the metal debris was recirculated between the rubbing surfaces. To prepare debris from polyethylene, a stainless steel block was rubbed over a polyethylene block submersed in liquid nitrogen.The shape of the metal debris was granular, whereas the polyethylene debris had a shted-like shape. The size distributions were determined from scanning electron micrographs, and it was found that the particles of the metal debris (stainless steel or cobalt-chrome alloy) ranged in sizes from 0.1-10 μ with 75% of all particles 〈2 μ in diameter. The size of polyethylene debris, expressed as the volume of an ellipsoid, ranged from 10-20,000 μ3 with 45% of all particles in the range of 400-2500 μ3.The x-ray diffraction pattern revealed that the debris of stainless steel consisted primarily of the face-centered cubic (fcc) alloy with small amounts of body-centered cubic (bcc) alloy and Fe3O4, whereas the cobalt-chrome debris consisted of the fcc alloy with a small amount of Cr2O3.The structure of the polyethylene debris was quite similar to that of the solid sample used in its preparation. The percent crystallinity Pc and the size of the crystalline regions D were slightly smaller in the debris than in the solid sample, i.e., Pc = 52 and 55%, D = 90 and 130 Å, in the debris and the solid, respectively.To test the suitability of the artificial debris for biocompatibility studies, stainless steel debris was implanted into knees of adult female New Zealand rabbits. Bacterial challenge studies indicated prolongation, but not increased susceptibility to infection.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820100503
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  • 4
    Electronic Resource
    Electronic Resource
    Contact finite element stress analysis of the hip joint (1985)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 3 (1985), S. 435-446 
    Details
    ISSN: 0736-0266
    Keywords: Acetabulum ; Hip joint ; Pressure distribution ; Contact stresses ; Bone stresses ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two-dimensional finite element analyses were conducted of the normal hip using contact elements at the joint surface. The models studied were constructed for a slice through the pubis, acetabulum, and ilium. In the analyses the proximal femur was pressed into the acetabulum and intraarticular pressures and principal stresses in the joint region were determined for different load magnitudes and directions and various boundary conditions. Three sets of boundary conditions were examined: (a) deformable pubic symphysis, (b) rigid pubic symphysis, and (c) simulations of experimental studies. In the deformable model the pubic symphysis was free to displace in the sagittal plane and rotate. In the rigid model the pubic symphysis was rigidly fixed. Superoposterior loading resulted in high-contact pressures at the acetabular dome for all sets of boundary conditions. For the deformable model subject to a more medially directed load the acetabulum closed in such a manner as to squeeze the head of the femur creating high-contact pressures superiorly and inferiorly. This resulted in significant compressive stresses in the superior dome cancellous bone and inferior cancellous bone. The cumulative effect of this squeezing action with normal biological remodeling may cause elongation of the femoral head resulting in asphericity and incongruity of the unloaded hip joint articular surfaces. Rigidly fixing the pubic symphysis stiffened the model and resulted in principal stress patterns that did not reflect trabecular density or orientations as well as those of the deformable pubic symphysis model. Finite element simulations of previous experimental studies modeled the close proximity of the fixation to the fixation to the excised acetablulum. These boundary conditions prevented the squeezing caused by pelvis deformations. The resulting contact areas, pressure distributions, and bone stresses were very different from those of more anatomic, deformable pubic symphysis model. These findings demonstrate the sensitivity of hip contact pressures and stresses to imposed boundary conditions and indicate that care should be taken to simulate anatomic conditions in experimental and theoretical studies.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100030406
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  • 5
    Electronic Resource
    Electronic Resource
    Contact finite element stress analysis of porous ingrowth acetabular cup implantation, ingrowth, and loosening (1987)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 5 (1987), S. 548-561 
    Details
    ISSN: 0736-0266
    Keywords: Acetabulum ; Total hip replacement ; Loosening ; Bone stresses ; Implant interface ; Porous ingrowth ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two-dimensional linear and contact finite element analyses were conducted of total hip arthroplasty using metal-backed, porous ingrowth acetabular components. The stress transmission characteristics from the component to the surrounding bone were given special attention. Resultant loads of 20 and 40° medial of vertical were studied, and the influence of adding a metal flange to the rim of the cup was evaluated. The results indicated that when a conventional metal-backed component (without a flange) is initially implanted and subjected to normal loading, these components may experience distraction between the component and the surrounding bone at inferior sites. Compressive stresses in the superior dome cancellous bone, however, will be substantial. If complete porous ingrowth is achieved, the superior dome compressive stresses will be reduced and substantial shear stresses created. In addition, high local bone stresses were found at the component rim. If bone ingrowth is achieved only in specific locations, stress transmission will be dictated by those locations and may differ markedly from the case of complete bone ingrowth. In the event that no porous ingrowth is achieved and a fibrous layer forms around the component, the interface stresses will be similar to those calculated for the natural hip. The addition of a flange to the rim of the cup will reduce the magnitude of the radial stresses transmitted to the cancellous bone superiorly and medially by directly transferring some of the load to the lateral wall of the pelvis. The flange will also help to relieve the high local stresses that are found at the component rim.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100050410
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of ingrowth, geometry, and material on stress transfer under porous-coated hip surface replacements (1988)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 6 (1988), S. 425-433 
    Details
    ISSN: 0736-0266
    Keywords: Surface replacement ; Prosthesis design ; Finite elements ; Stress shielding ; Porous ingrowth ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Three different interface geometries for porous ingrowth surface replacements of the hip were examined using two-dimensional linear and non-linear contact finite element analyses. The results indicate that incorporation of a nearly flat prosthesis interface between the surface replacement and the underlying cancellous bone may reduce stress shielding and improve stress transfer from the component. For all designs analyzed, the bone stress shielding was insensitive to component material stiffness when the elastic modulus was 〉30 MPa. The use of titanium instead of cobalt-chrome (Co-Cr) as the prosthesis material therefore had a negligible effect on stress shielding.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100060314
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