4 results
Now showing1 - 4 of 4
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Backside wear of tibial polyethylene components is affected by gait pattern: A knee simulator study using rare earth tracer technology(2020-07-01); ; ; ; The aim of this study was to determine the effect of two in-vivo–determined gait patterns, one with low and one with high anteroposterior (AP) motion, on total and backside polyethylene insert wear in comparison with the ISO (International Organization for Standardization) standard 14243-3. In order to differentiate and accurately quantify topside and backside wear, a novel technique was employed where different lanthanide tracers were incorporated into the polyethylene during manufacture. Wear particle analysis was conducted following established protocols. For all tested liners and motion protocols, the chemically calculated wear rates correlated closely with gravimetrically determined wear. Both in vivo motion groups displayed higher wear rates than the ISO group following the order of the AP motion amplitudes. Backside wear for ISO constituted 2.76% ± 0.90% (mean ± SE) of the total wear, increasing significantly to 15.8% ± 3.2% for the low AP and further increasing to 19.3% ± 0.95% for the high AP motion protocol. The mean wear particle sizes were under 200 nm for all three motion patterns, being largest for the protocol with high AP motion. Particle release from the low and high AP gait patterns was 1.9 to 2.8 times that from the ISO protocol. Testing for the proportion of backside wear across various activities of daily living should be an important consideration in evaluating knee prostheses wear.Publicationtype: Journal Article77 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Microstructure of retrievals made from standard cast HC-CoCrMo alloys(ASTM International, 2013); ; ; ; During the past decade, self-mating metal bearings based on cobalt- chromium-molybdenum (CoCrMo) alloys have become very popular in total hip replacements and hip resurfacings. This led to a market share of more than 35 % for metal-on-metal (MoM) bearings in the United States before several cases of high wear with biologic consequences led to a sharp drop in popularity. In part, these failures are a result of a very shallow understanding of the wear mechanisms in MoM joints and their relation to the microstructure. In order to find such a relation, one has to keep in mind that the microstructures of metallic materials depend distinctly on the entire production sequence. In addition, they change markedly under tribological stresses. This paper does not discuss the wear of any specific retrieval or even try to relate that to the specific microstructure, because such a task would be impossible based on the unknown loading history of such retrievals. Thus, we depict only the possible range of microstructures from standardized high carbon (HC)-CoCrMo retrievals. These reveal different types of hard phases: carbides and/or intermetallic phases. Some are fine (<10μm) and homogeneously distributed, whereas others appear as thin (<1 μm) and brittle cord-shaped arrangements at grain or dendrite boundaries. Coarser (>30 μm) types of mixed hard phases, which consist of carbides and interme-tallic phases, often show microcracks already below the articulating surfaces. Such subsurface microcracks are known to destabilize the gradient below the surface and the balance between tribochemical reactions and surface fatigue. In this paper, the microstructures of retrievals manufactured from standard cast CoCrMo alloys are shown and evaluated.Publicationtype: Conference Paper45 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effect of europium(II) stearate on the mechanical properties and the oxidation resistance of UHMWPE(Elsevier, 2010-11-21); ; ; ; The objective of this pilot study is to investigate the effect of europium(II) stearate additive on the mechanical properties and oxidation resistance of an ultra-high molecular weight polyethylene (UHMWPE), which has been used as an articulating surface in prosthetic devices for many years. It is hypothesized in this study that combining the UHMWPE with lanthanide stearates could enhance oxidation resistance, leading to better preservation of the material's mechanical integrity.Compression molded UHMWPE was doped at 0, 375 and 750 ppm of europium(II) stearate, γ-irradiated to 35 kGy in a nitrogen atmosphere, and accelerated aged in accordance with the ASTM standard F2003-02. Non-irradiated and nonaged samples were used as controls. Miniature samples were comparatively tested for mechanical properties using the small punch test. Oxidation indices (OIs) were obtained through the FTIR spectroscopy on thin film sections of all irradiated samples.The UHMWPE doped with the europium(II) stearate had the same small punch test curve shape as the conventional UHMWPE control; the ultimate displacement remained unchanged (approximately 4.33±0.02 mm), while the ultimate load and work-to-failure exhibited only small changes (<7.5% and <5.0%, respectively). The doped material was more resistant to oxidation than the control material, retaining 83% of its as-irradiated work-to-failure after irradiation and accelerated aging, versus only 53% for the control. Accelerated aging changed the average oxidation index of the control group from 0.07 to 0.40; whereas the average oxidation indices changed from 0.03 to 0.15 and from 0.05 to 0.13 for the 375 ppm and the 750 ppm doped condition, respectively.Publicationtype: Journal ArticleScopus© Citations 4 27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Orientation of the acetabular component : a comparison of five navigation systems with conventional surgical technique(Ed. Soc. of Bone and Joint Surgery, 2006-10-01); ; ; We compared the orientation of the acetabular component obtained by a conventional manual technique with that using five different navigation systems. Three surgeons carried out five implantations of an acetabular component with each navigation system, as well as manually, using an anatomical model. The orientation of the acetabular component, including inclination and anteversion, and its position was determined using a co-ordinate measuring machine. The variation of the orientation of the acetabular component was higher in the conventional group compared with the navigated group. One experienced surgeon took significantly less time for the procedure. However, his placement of the component was no better than that of the less experienced surgeons. Significantly better inclination and anteversion (p < 0.001 for both) were obtained using navigation. These parameters were not significantly different between the surgeons when using the conventional technique (p = 0.966). The use of computer navigation helps a surgeon to orientate the acetabular component with less variation regarding inclination and anteversion. © 2006 British Editorial Society of Bone and Joint Surgery.Publicationtype: Journal Article6