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T J Joyce - One of the best experts on this subject based on the ideXlab platform.
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Hip Simulator testing of the taper trunnion junction and bearing surfaces of contemporary metal on cross linked polyethylene Hip prostheses
Journal of Biomedical Materials Research Part B, 2020Co-Authors: R M Bhalekar, Simon Smith, T J JoyceAbstract:: Adverse reaction to metal debris released from the taper-trunnion junction of modular metal-on-polyethylene (MoP) total Hip replacements (THRs) is an issue of contemporary concern. Therefore, a Hip Simulator was used to investigate material loss, if any, at both the articulating and taper-trunnion surfaces of five 32-mm metal-on-cross-linked-polyethylene THRs for 5 million cycles (Mc) with a sixth joint serving as a dynamically loaded soak control. Commercially available cobalt-chromium-molybdenum femoral heads articulating against cross-linked polyethylene (XLPE) acetabular liners were mounted on 12/14 titanium (Ti6Al4V) trunnions. Weight loss (mg) was measured gravimetrically and converted into volume loss (mm3 ) for heads, liners, and trunnions at regular intervals. Additionally, posttest volumetric wear measurements of the femoral tapers were obtained using a coordinate measuring machine (CMM). The surface roughness (Sa) of femoral tapers was measured posttest. After 5 Mc, the mean volumetric wear rate for XLPE liners was 2.74 ± 0.74 mm3 /Mc. The CMM measurements confirmed material loss from the femoral taper with the mean volumetric wear rate of 0.045 ± 0.024 mm3 /Mc. The Sa on the worn area of the femoral taper showed a significant increase (p < 0.001) compared with the unworn area. No other long-term Hip Simulator tests have investigated wear from the taper-trunnion junction of contemporary MoP THRs. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:156-166, 2020.
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wear at the taper trunnion junction of contemporary ceramic on ceramic Hips shown in a multistation Hip Simulator
Journal of Biomedical Materials Research Part B, 2019Co-Authors: R M Bhalekar, Simon Smith, T J JoyceAbstract:: Ceramic-on-ceramic (CoC) total Hip replacements (THR) have a substantially lower wear rate than metal-on-polyethylene (MoP) Hips, as shown by Hip Simulator testing. However, the revision rates of CoC and MoP Hips are comparable. To try and explain this discrepancy the wear, at both the bearing surfaces and taper-trunnion interface of 36 mm BIOLOXdelta CoC THRs, mounted on 12/14 titanium (Ti6Al4V) trunnions was investigated using a Hip Simulator (n = 3) and a dynamically loaded CoC sample in a separate test station. Wear was assessed gravimetrically and surface roughness measurements of the articulating and taper surfaces taken at regular intervals. Scanning electron microscopy, surface roughness, and gravimetric measurements of trunnions was performed. After 5 million cycles, the mean total wear from the ceramic articulating surfaces was 0.25 mm3 from the Hip Simulator test, and that from the titanium trunnions was 0.29 mm3 . This metal wear may provide an explanation for adverse reaction to metal debris found in contemporary CoC Hip joints. It is therefore vital to consider taper-trunnion wear in preclinical testing of artificial Hip joints. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1199-1209, 2019.
Ian C. Clarke - One of the best experts on this subject based on the ideXlab platform.
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Validation of a 3D CT method for measuring linear and -volumetric wear of acetabular cups - a Hip Simulator study
Acta Orthopaedica, 2020Co-Authors: Anneli Jedenmalm, Ian C. Clarke, Fritjof Nilsson, Douglas D. Green, Ulf W. Gedde, Andreas Stark, Henrik OlivecronaAbstract:Validation of a 3D CT method for measuring linear and -volumetric wear of acetabular cups - a Hip Simulator study
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Two retrieved cups compared to Hip Simulator wear study
2020Co-Authors: Kengo Yamamoto, Ian C. Clarke, Toshinori Masaoka, M. Manaka, Hironobu Oonishi, Hiromu Shoji, Keiichi Kawanabe, Atsuhiro ImakiireAbstract:ABSTRACT We studied the micro-wear phenomena of unique, extensively cross-linked polyethylene cups (cross-linked with 1,000 kGy-irradiation) that had been used briefly in Japan. Two retrievals (at 15 years) came from the Japanese “SOM” Hip system (implanted 1971–78). These were compared to a set of 0kGy and 500–1,500 kGy cups run in our Hip Simulator. The poly-ethylene cups that had not been cross-linked had the greatest wear. The worn areas had a burnished appear-ance and were clearly separated from the unworn region by a distinct ridge-line. The worn areas had lost all machine tracks, showed a large amount of UHMWPE ʻflowʼ, and long PE fibrils. The associated surface rip-pling was degraded. These features were considered synonymous with severe polyethylene wear. In contrast, the worn areas in the very cross-linked cups had a vis-ibly matte surface and no ridge-line. Micro-examination showed that the machine tracks were still present. Ripple formations were less obvious than in the cups that were not cross-linked, polyethylene surface fibrils were scarcer and all the fibrils were much smaller than in the cups that were not crosslinked. Our two retrieved cups and the Simulator cups confirmed the greater wear-resistance of very cross-linked polyethylene. It should also be noted that the SOM cup design and processing were unique and differed greatly from that of modern polyethylene cups.
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Cross-Linked UHMWPE on Alumina Total Hip Arthroplasty
Arthroplasty 2000, 2020Co-Authors: Hironobu Oonishi, Victoria Good, Ian C. Clarke, Hirokazu Amino, Shingo MasudaAbstract:Summary. The clinical wear rate of cross-linked polyethylene cups (RCH 1000) irra diated in air with 100 Mrad (clinical use, 1971-1978) decreased to 18%. Tensile strength and elongation decreased, but deterioration did not progress, and the tough ness greatly increased in retrieved 100-Mrad polyethylene (PE). The degree of oxida tion after 18 years slightly increased. In the Hip Simulator test using 30% bovine serum as lubricant, cross-linked cups irradiated with 50-150 Mrad did not show detectable wear. Wear of ultrahigh molecular weight polyethylene (UHMWPE) irradiated with 6.5 Mrad (Aeonian) decreased to 3% by the Hip Simulator test without deterioration of physical properties. Oxidation caused by free radicals produced by gamma-ray sterilization was extremely low.
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US perspective on Hip Simulator wear testing of BIOLOX® delta in’ severe’ test modes
Ceramics in Orthopaedics, 2020Co-Authors: Ian C. Clarke, Paul Allen Williams, D. Green, T. Donaldson, G. PezzottiAbstract:A ceramic on ceramic (COC) Simulator wear study was run with 36mm Biolox® implants under’ severe’ microseparation test mode. The implants included the zirconia-toughened alumina (ZTA: Biolox® delta, ‘d’) with alumina used as the historical control (Biolox® forte, ‘f’). The four combinations (ball-cup: dd, df, fd and ff) were run simultaneously in a Hip Simulator to 5 million cycles duration (5Mc). The femoral balls were 36mm diameter and four material pairings were run with preset ball/cup diametral clearances. All combinations demonstrated stripe wear phenomenon on both balls and cups. The stripes began immediately in the runin phase (100,000 cycles) as well-defined, narrow scars that gradually expanded over the duration of the study. For the cups, there was a narrow superior stripe region along the rim that expanded circumferentially with test duration. The ff combination showed the greatest stripe expansion that also expanded rapidly into the main wear zone. The appearance of such narrow stripes in run-in phase was comparable to prior microseparation Simulator studies and short-term ceramic retrieval studies. The gradual expansion of our Simulator stripes compared well to our long-term ceramic retrievals with 15 to 22 year use in-vivo.
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Wear of Alumina-on-Alumina Total Hip Prosthesis: Effect of Diametrical Clearance and Lubricant on Hip Simulator Test
Arthroplasty 2000, 2020Co-Authors: Hironobu Oonishi, Victoria Good, Ian C. Clarke, Masaru Ueno, Hirokazu AminoAbstract:Summary. The wear test of an alumina-on-alumina total Hip prosthesis (THP) was performed on a Hip Simulator by using saline and 90% bovine serum, respectively; 2S-mm alumina/alumina acetabular cups with matching femoral heads were tested. The out-of-roundness was less than 2 flm, the surface roughness was less than 0.02 flm, and crystal size was 1.4 flm on average. The diametrical clearances were 10-20 flm when saline was used as lubricant, and the clearances were 20-30 flm, 60-70 flm, and 90-100 flm when using 90% bovine serum. The wear trends were biphasic, "run-in;' and "steady-state" phase. "Run-in" wear rates in the case of saline and 90% bovine serum were O.OS and 0.27 mm) /million cycles, respectively; "steady state" wear rates in the case of saline and 90% bovine serum were 0.0015 and 0.004mm3/million cycles, respectively; and "run-in" and "steady-state" wear rates in 90% bovine serum were threefold higher than those in saline. Alumina-on-alumina wear was extremely low in diametrical clearance between 10 to 100 flm in both saline and bovine serum.
R M Bhalekar - One of the best experts on this subject based on the ideXlab platform.
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Hip Simulator testing of the taper trunnion junction and bearing surfaces of contemporary metal on cross linked polyethylene Hip prostheses
Journal of Biomedical Materials Research Part B, 2020Co-Authors: R M Bhalekar, Simon Smith, T J JoyceAbstract:: Adverse reaction to metal debris released from the taper-trunnion junction of modular metal-on-polyethylene (MoP) total Hip replacements (THRs) is an issue of contemporary concern. Therefore, a Hip Simulator was used to investigate material loss, if any, at both the articulating and taper-trunnion surfaces of five 32-mm metal-on-cross-linked-polyethylene THRs for 5 million cycles (Mc) with a sixth joint serving as a dynamically loaded soak control. Commercially available cobalt-chromium-molybdenum femoral heads articulating against cross-linked polyethylene (XLPE) acetabular liners were mounted on 12/14 titanium (Ti6Al4V) trunnions. Weight loss (mg) was measured gravimetrically and converted into volume loss (mm3 ) for heads, liners, and trunnions at regular intervals. Additionally, posttest volumetric wear measurements of the femoral tapers were obtained using a coordinate measuring machine (CMM). The surface roughness (Sa) of femoral tapers was measured posttest. After 5 Mc, the mean volumetric wear rate for XLPE liners was 2.74 ± 0.74 mm3 /Mc. The CMM measurements confirmed material loss from the femoral taper with the mean volumetric wear rate of 0.045 ± 0.024 mm3 /Mc. The Sa on the worn area of the femoral taper showed a significant increase (p < 0.001) compared with the unworn area. No other long-term Hip Simulator tests have investigated wear from the taper-trunnion junction of contemporary MoP THRs. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:156-166, 2020.
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wear at the taper trunnion junction of contemporary ceramic on ceramic Hips shown in a multistation Hip Simulator
Journal of Biomedical Materials Research Part B, 2019Co-Authors: R M Bhalekar, Simon Smith, T J JoyceAbstract:: Ceramic-on-ceramic (CoC) total Hip replacements (THR) have a substantially lower wear rate than metal-on-polyethylene (MoP) Hips, as shown by Hip Simulator testing. However, the revision rates of CoC and MoP Hips are comparable. To try and explain this discrepancy the wear, at both the bearing surfaces and taper-trunnion interface of 36 mm BIOLOXdelta CoC THRs, mounted on 12/14 titanium (Ti6Al4V) trunnions was investigated using a Hip Simulator (n = 3) and a dynamically loaded CoC sample in a separate test station. Wear was assessed gravimetrically and surface roughness measurements of the articulating and taper surfaces taken at regular intervals. Scanning electron microscopy, surface roughness, and gravimetric measurements of trunnions was performed. After 5 million cycles, the mean total wear from the ceramic articulating surfaces was 0.25 mm3 from the Hip Simulator test, and that from the titanium trunnions was 0.29 mm3 . This metal wear may provide an explanation for adverse reaction to metal debris found in contemporary CoC Hip joints. It is therefore vital to consider taper-trunnion wear in preclinical testing of artificial Hip joints. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1199-1209, 2019.
Vesa Saikko - One of the best experts on this subject based on the ideXlab platform.
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Effect of increased load on the wear of a large diameter metal-on-metal modular Hip prosthesis with a high inclination angle of the acetabular cup
Tribology International, 2016Co-Authors: Vesa SaikkoAbstract:Abstract In some earlier Hip Simulator studies of large-diameter metal-on-metal (MoM) Hip prostheses high, unexplained variation in wear has been observed. In the present study it was found that high variation occurs when the tribological endurance limit of the MoM device in question is being approached. When the limit is exceeded, high wear takes place uniformly, and the variation is low. Below the limit, both the wear and its variation are low. The endurance limit was exceeded by increasing the peak load from 2 kN to 3 kN, to simulate obesity. The acetabular cup inclination angle was high, 70°. Potential clinical wear problems can be predicted by Hip Simulator studies provided that relevant adverse test conditions are included.
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Adverse condition testing with Hip Simulators
Biotribology, 2015Co-Authors: Vesa SaikkoAbstract:Recent clinical failures and abnormal sounds observed in certain prosthetic Hip designs have directed attention to adverse condition Hip Simulator testing. In the present study, Hip Simulator wear and friction tests were made with a macroscopic separation of the bearing surfaces in the swing phase, steep acetabular cup position, increased load, poor or lacking lubrication, roughened bearing surfaces including titanium third bodies, and with combinations of these. The only conditions that resulted in squeaking were dry sliding with alumina-on-alumina and metal-on-metal, and an extreme peak load of 4 kN with serum lubricated metal-on-metal. The wear rate of metal-on-metal increased by an order of magnitude when the cup position was steep, 64°, compared with the optimal position of 48°. The increase of the peak load from 2 kN to 3 kN with the cup position of 48° increased the running-in wear of metal-on-metal, but the steady state wear rates were equally low, of the order of 1 mg per one million cycles. Crosslinked polyethylene was the superior cup material under adverse conditions, including dry sliding and roughened femoral head.
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Force track analysis of contemporary Hip Simulators.
Journal of Biomechanics, 2003Co-Authors: Olof Calonius, Vesa SaikkoAbstract:Abstract In an earlier paper, the authors presented the first verified method of computation of slide tracks in the relative motion between femoral head and acetabular cup of total Hip prostheses. The method was applied for gait and for two Hip Simulator designs, and in a subsequent paper, for another eight designs. In the present paper, the track drawn by the resultant contact force, the so-called force track, was studied in depth. The variations of sliding distance, sliding velocity and direction of sliding during a cycle, all of which are important with respect to wear, were computed for gait and for 11 Hip Simulator designs. Moreover, the product of the instantaneous load and increment of sliding distance was numerically integrated over a cycle. This integral makes it possible to compare clinical wear rates with those produced by Hip Simulators in terms of a wear factor. For the majority of contemporary Hip Simulators, the integral has so far been unknown. The computations revealed considerable differences, which are likely to explain the substantial differences in wear produced by the Simulators. With the most common head diameter, 28 mm, the ranges for sliding distance per cycle, mean sliding velocity, total change of direction of sliding and integral were: 19.7–34.3 mm, 19.7–49.0 mm/s, 360–1513°, and 17.4–43.5 N m, respectively.
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slide track analysis of eight contemporary Hip Simulator designs
Journal of Biomechanics, 2002Co-Authors: Olof Calonius, Vesa SaikkoAbstract:In an earlier paper, the authors presented a new method of computation of slide tracks in the relative motion between femoral head and acetabular cup of total Hip prostheses. For the first time, computed tracks were verified experimentally and with an alternative method of computation. Besides being an efficient way to illustrate Hip kinematics, the shapes of the slide tracks are known to be of fundamental importance regarding the wear behaviour of prostheses. The verified method was now applied to eight contemporary Hip Simulator designs. The use of correct motion waveforms and an Euler sequence of rotations in each case was again found to be essential. Considerable differences were found between the Simulators. For instance, the shapes of the tracks drawn by the resultant contact force included a circle, ellipse, irregular oval, leaf, twig, and straight line. Computation of tracks correctly for the most widely used Hip Simulator, known as biaxial, was made possible by the insight that the device is actually three-axial. Slide track patterns have now been computed for virtually all contemporary Hip Simulators, and both for the heads and for the cups. This comparative analysis forms a valuable basis for studies on the relationsHip between the type of multidirectional motion and wear. These studies can produce useful information for the design of joint Simulators, and improve the understanding of wear phenomena in prosthetic joints.
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low wear and friction in alumina alumina total Hip joints a Hip Simulator study
Acta Orthopaedica Scandinavica, 1998Co-Authors: Vesa Saikko, Hansgeorg PfaffAbstract:We studied the wear of state-of-the-art alumina/alumina total Hip joints with the uniaxial five-station, and the three-axis single-station Hip joint Simulators of Helsinki University of Technology, The diameters of the joints were 26, 28 and 32 mm. Visual examination and weighing of the components showed no wear. Scanning electron microscopy showed that (a) the wear marks were slight, consisting of removal of grains, multidirectional grooving and mild abrasion, (b) the wear mechanisms were similar to those seen in components removed from patients, and (c) there was no marked difference in the specimens worn in the uniaxial vs. three-axis Simulator. The coefficient of friction was measured throughout the 5 million cycle wear test with the three-axis Simulator. The average value was 0.007. We conclude that alumina/alumina joints had low wear and friction under the present test conditions. The results are promising, since minimal wear is one of the prerequisites for long-term success in prosthetic joints.
William H Harris - One of the best experts on this subject based on the ideXlab platform.
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comparison of Hip Simulator wear of 2 different highly cross linked ultra high molecular weight polyethylene acetabular components using both 32 and 38 mm femoral heads
Journal of Arthroplasty, 2007Co-Authors: Daniel M Estok, Orhun K Muratoglu, Brian R Burroughs, William H HarrisAbstract:Abstract Much evidence suggests that ultra high molecular weight polyethylene (UHMWP) irradiated to 9.5 Mrad has lower wear than UHMWP given 5 Mrad. Curiously, highly cross-linked polyethylenes gain weight during Hip Simulator testing. We postulated that ( a ) UHMWP irradiated to 9.5 Mrad would wear less than UHMWP irradiated to 5 Mrad UHMWP, ( b ) articulation against 38-mm heads would accentuate this difference, and ( c ) weight gain of highly cross-linked material reflects the inadequacy of load soak controls. We compared 9.5 versus 5 Mrad polyethylene in Hip Simulator wear tests, with both load soak corrections and with novel "motion soak" corrections. The 9.5-Mrad material wore less than 5-Mrad material for 32- and 38-mm heads. Motion soak corrections were more accurate than load soak corrections.
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third body wear of highly cross linked polyethylene in a Hip Simulator
Journal of Arthroplasty, 2003Co-Authors: Charles R Bragdon, Murali Jasty, Orhun K Muratoglu, Daniel O Oconnor, William H HarrisAbstract:Abstract The wear performance of a radiation cross-linked melted ultrahigh-molecular-weight polyethylene (UHMWPE) articulating against 28-mm cobalt chrome femoral heads in the presence of third-body particulate debris was investigated in a Hip Simulator and compared with the wear of conventional UHMWPE. Particles of aluminum oxide or bone cement containing barium sulfate were added to the serum. In the presence of aluminum oxide particles, the incremental wear rates of conventional UHMWPE averaged as high as 149 ± 116 mg/million cycles compared with 37 ± 38 mg/million cycles for the highly cross-linked components. The difference in the average weight loss was statistically significant at P
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Analysis of the kinematics of different Hip Simulators used to study wear of candidate materials for the articulation of total Hip arthroplasties
Journal of Orthopaedic Research, 1998Co-Authors: Balaji S. Ramamurti, Murali Jasty, Daniel M Estok, William H HarrisAbstract:: We developed an analytical technique to determine the paths traced by specific points on the femoral head against the acetabulum in the human Hip joint during gait. The purpose of the study was to apply this technique to the mechanical Hip Simulators chosen to conduct wear tests on polymeric acetabular liners used in total Hip replacements. These Simulators differ from one another in the type of motion produced, apart from other variables such as type of lubricant and head position. Due to the variation in the kinematics between the machines, the paths traced by the points on the femoral head against the acetabular liner ranged from simple linear traces to figure-8 loops and quasi-elliptical paths during a single Simulator cycle. The distances traveled by these points during the same period also varied appreciably among the different Hip Simulator designs. These results are important when combined with other studies that have shown that kinematics can play an important role in the outcome of in vitro wear experiments. The kinematic differences quantified in this study can partially explain the substantial differences in wear data reported from different Simulator designs and also underscore the usefulness of the technique described in this study in judging the results from different Hip Simulator experiments.