The Experts below are selected from a list of 29748 Experts worldwide ranked by ideXlab platform
Ian C Clarke - One of the best experts on this subject based on the ideXlab platform.
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a new method for simulating edge wear mechanics in tha relevant to patient gait a ten Million Cycle study with 60 mm mom bearings
Orthopaedic Proceedings, 2018Co-Authors: Ian C Clarke, Thomas Halim, J Shelton, Thomas DonaldsonAbstract:There will be occasions when standards and guidelines stymie the development of new methods. For example, the majority of simulator studies utilized the international guideline specifying that cups...
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acetabular cups in 60 mm metal on metal bearings subjected to dynamic edge loading with 70 peak inclination in 10 Million Cycle simulator study
Lubricants, 2017Co-Authors: Ian C Clarke, Thomas Halim, E Smith, Thomas DonaldsonAbstract:Wear simulation of total-hip arthroplasty (THA) involves hip biomechanics, tribology, bearing designs and cup wear-patterns. This is the first demonstration of cup edge-loading using the “Inverted-cup” test mode. Benefits included, (i) clinically relevant wear-patterns, and (ii) cup inclinations varying from ideal to edge-loaded during each 1-s simulator Cycle. The 60 mm head and cup bearings in metal-on-metal (MOM) hip joints showed run-in and steady-state wear phases to 10-Million Cycles (Mc). MOM edge-wear was not unduly high at 1.7 mm3/Mc overall, this 3-fold higher than 60 mm MOM study without edge-loading. One MOM outlier averaged 2.7 mm3/Mc, this representing the break-away wear (BAW) phenomena. A surprising result was that cups contributed 75–93% of total wear. The most disturbing conclusion from review of laboratory studies was that MOM wear-rates varied 1 to >30 mm3/Mc for reasons not understood. These data suggested a new hypothesis, that MOM bearings were very sensitive to external stimuli, be they simulator artifact or patient related.
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a new method for simulating edge wear mechanics in tha relevant to patient gait a ten Million Cycle study with 60 mm mom bearings
Journal of Bone and Joint Surgery-british Volume, 2017Co-Authors: Ian C Clarke, Thomas Halim, J Shelton, Thomas DonaldsonAbstract:There will be occasions when standards and guidelines stymie the development of new methods. For example, the majority of simulator studies utilized the international guideline specifying that cups will be positioned “Anatomically” (ISO-14242), i.e. acetabular liner is positioned above oscillating femoral head (Fig. 1). This can be disadvantageous for studies of “edge wear” in steeply inclined cups (Williams 2008, Leslie 2009, Angadji 2009). Importantly, such an “Anatomical” cup is fixed with respect to the resultant load-axis (Fig. 1d: R). This produces a constant edge-wear throughout the simulator's Cycle. Our supposition was that it is more likely patients experience edge-wear intermittently, i.e. at extremes of motion. This intermittent effect can be best replicated with the cup mounted “Inverted” (Fig. 2), the rotating cam allowing precise selection of edge-wear at extreme of motion (Fig. 2c). An advantage of this method is that the wear-pattern in the orbiting cup is now much larger (Bowsher, 2009: x3.8 ratio), making edge-wear easier to achieve. Our hypotheses were that (1) the Inverted test would provide both “normal” and “edge wear” as defined (Clarke, 2015: steep-cup algorithm), (2) MOM wear rates under edge-wear condition would be greater than in standard simulator tests (Bowsher 2016) and (2) intermittent edge-wear of MOM cups (Inverted) would be less severe than in prior Anatomical tests (Williams 2008, Leslie 2009, Angadji 2009). The 60mm MOM bearings (DJO, Austin TX) were selected on the basis of prior Anatomical study (Bowsher, 2009), were run with cups Inverted, using identical test methods as before, in the orbital simulator. Wear-rates in 60mm heads revealed both run-in and steady-state wear phases (Fig. 3a). The weight-loss method showed perturbations due to protein contaminants but these appeared of minor concern over 10-Million Cycles. One cup was damaged during set-up, did not recover, and was not included in the analysis (Fig. 3b). Cup wear rates over 10-Million Cycles appeared very stable with excellent consistency (Fig. 3c). By end of test, the edge-wearing cups averaged 3.7 times higher wear than mating heads. Overall MOM wear averaged 1.6mm3 per Million Cycles. Apart from the first 100,000 Cycles of run-in, no lubricant changed color during entire test. In this first study of its kind, we demonstrated both normal and edge-wear wear-patterns in accordance with predictions of the steep-cup algorithm (Clarke 2015), satisfying hypothesis #1. Wear rates with Inverted cups averaged 2.7 times greater wear than those in similar Anatomical study (Bowsher, 2009), satisfying hypothesis #2. The 60mm MOM wear rates Inverted were mid-range to those in the prior steep-cup Anatomical tests (range 1.3 – 1.9mm3 per 106 Cycles). This neither satisfied nor eliminated hypothesis #3, perhaps due to confounding effects, i.e. different designs, MOM diameters and methods. In conclusion, the Inverted test in the simulator appears to offer considerable merit, perhaps analogous to patients who experience edge-wear only intermittently. In contrast the Anatomical test mode appears analogous to patients with mal-positioned cups, who therefore walk on the cup rim constantly throughout their gait Cycle.
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wear of sequentially enhanced 9 mrad polyethylene in 10 Million Cycle knee simulation study
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Riichiro Tsukamoto, P A Williams, Hiromu Shoji, Kazuo Hirakawa, Kengo Yamamoto, Mikiko Tsukamoto, Ian C ClarkeAbstract:Highly crosslinked polyethylene (HXPE) has been shown to be effective in reducing wear in total hip replacements. HXPE has not found widespread use in TKR, because the crosslinking inevitably leads to reductions in critical properties such as toughness and fatigue strength. Sequentially enhanced crosslinking (SXPE) have been suggested for improved wear resistance for tibial inserts with maintenance of mechanical properties and anticipated high oxidation resistance superior to conventional polyethylene (XLPE). We compared the wear of SXPE (9Mrad) to XLPE inserts (3Mrad) to 10 Million Cycles. Triathlon™ femoral condyles were identical in both. This is the first wear study of SXPE inserts. According to the power law relating irradiation dose to wear of XLPE inserts, wear of 9 Mrad inserts should be reduced by 70% compared to 3Mrad controls. The wear rates of the SXPE inserts were reduced by 86% at 10 Million Cycles duration, somewhat greater than predicted. The one prior investigation by the manufacturer reported a 79% wear reduction for SXPE compared to controls in a 5 Million Cycle simulator study in knee design and test parameters. There were important differences between the two studies. Nevertheless there clearly appeared to be a major benefit for sequentially enhanced polyethylene in tibial inserts. This combined wear reduction of 80-85% with improved oxidation resistance and retention of mechanical properties may prove beneficial for active patients who may otherwise risk high wear rates over many years of use. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Frederick F Buechel - One of the best experts on this subject based on the ideXlab platform.
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titanium nitride ceramic film against polyethylene a 48 Million Cycle wear test
Clinical Orthopaedics and Related Research, 1995Co-Authors: Michael J Pappas, G Makris, Frederick F BuechelAbstract:Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce > 40 Million motion Cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37 degrees C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was < 0.02 mm, and < 2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.
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titanium nitride ceramic film against polyethylene a 48 Million Cycle wear test polyethylene wear
Clinical Orthopaedics and Related Research, 1995Co-Authors: Michael J Pappas, G Makris, Frederick F BuechelAbstract:Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce >40 Million motion Cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37° C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was <0.02 mm, and <2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.
Thomas Donaldson - One of the best experts on this subject based on the ideXlab platform.
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a new method for simulating edge wear mechanics in tha relevant to patient gait a ten Million Cycle study with 60 mm mom bearings
Orthopaedic Proceedings, 2018Co-Authors: Ian C Clarke, Thomas Halim, J Shelton, Thomas DonaldsonAbstract:There will be occasions when standards and guidelines stymie the development of new methods. For example, the majority of simulator studies utilized the international guideline specifying that cups...
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acetabular cups in 60 mm metal on metal bearings subjected to dynamic edge loading with 70 peak inclination in 10 Million Cycle simulator study
Lubricants, 2017Co-Authors: Ian C Clarke, Thomas Halim, E Smith, Thomas DonaldsonAbstract:Wear simulation of total-hip arthroplasty (THA) involves hip biomechanics, tribology, bearing designs and cup wear-patterns. This is the first demonstration of cup edge-loading using the “Inverted-cup” test mode. Benefits included, (i) clinically relevant wear-patterns, and (ii) cup inclinations varying from ideal to edge-loaded during each 1-s simulator Cycle. The 60 mm head and cup bearings in metal-on-metal (MOM) hip joints showed run-in and steady-state wear phases to 10-Million Cycles (Mc). MOM edge-wear was not unduly high at 1.7 mm3/Mc overall, this 3-fold higher than 60 mm MOM study without edge-loading. One MOM outlier averaged 2.7 mm3/Mc, this representing the break-away wear (BAW) phenomena. A surprising result was that cups contributed 75–93% of total wear. The most disturbing conclusion from review of laboratory studies was that MOM wear-rates varied 1 to >30 mm3/Mc for reasons not understood. These data suggested a new hypothesis, that MOM bearings were very sensitive to external stimuli, be they simulator artifact or patient related.
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a new method for simulating edge wear mechanics in tha relevant to patient gait a ten Million Cycle study with 60 mm mom bearings
Journal of Bone and Joint Surgery-british Volume, 2017Co-Authors: Ian C Clarke, Thomas Halim, J Shelton, Thomas DonaldsonAbstract:There will be occasions when standards and guidelines stymie the development of new methods. For example, the majority of simulator studies utilized the international guideline specifying that cups will be positioned “Anatomically” (ISO-14242), i.e. acetabular liner is positioned above oscillating femoral head (Fig. 1). This can be disadvantageous for studies of “edge wear” in steeply inclined cups (Williams 2008, Leslie 2009, Angadji 2009). Importantly, such an “Anatomical” cup is fixed with respect to the resultant load-axis (Fig. 1d: R). This produces a constant edge-wear throughout the simulator's Cycle. Our supposition was that it is more likely patients experience edge-wear intermittently, i.e. at extremes of motion. This intermittent effect can be best replicated with the cup mounted “Inverted” (Fig. 2), the rotating cam allowing precise selection of edge-wear at extreme of motion (Fig. 2c). An advantage of this method is that the wear-pattern in the orbiting cup is now much larger (Bowsher, 2009: x3.8 ratio), making edge-wear easier to achieve. Our hypotheses were that (1) the Inverted test would provide both “normal” and “edge wear” as defined (Clarke, 2015: steep-cup algorithm), (2) MOM wear rates under edge-wear condition would be greater than in standard simulator tests (Bowsher 2016) and (2) intermittent edge-wear of MOM cups (Inverted) would be less severe than in prior Anatomical tests (Williams 2008, Leslie 2009, Angadji 2009). The 60mm MOM bearings (DJO, Austin TX) were selected on the basis of prior Anatomical study (Bowsher, 2009), were run with cups Inverted, using identical test methods as before, in the orbital simulator. Wear-rates in 60mm heads revealed both run-in and steady-state wear phases (Fig. 3a). The weight-loss method showed perturbations due to protein contaminants but these appeared of minor concern over 10-Million Cycles. One cup was damaged during set-up, did not recover, and was not included in the analysis (Fig. 3b). Cup wear rates over 10-Million Cycles appeared very stable with excellent consistency (Fig. 3c). By end of test, the edge-wearing cups averaged 3.7 times higher wear than mating heads. Overall MOM wear averaged 1.6mm3 per Million Cycles. Apart from the first 100,000 Cycles of run-in, no lubricant changed color during entire test. In this first study of its kind, we demonstrated both normal and edge-wear wear-patterns in accordance with predictions of the steep-cup algorithm (Clarke 2015), satisfying hypothesis #1. Wear rates with Inverted cups averaged 2.7 times greater wear than those in similar Anatomical study (Bowsher, 2009), satisfying hypothesis #2. The 60mm MOM wear rates Inverted were mid-range to those in the prior steep-cup Anatomical tests (range 1.3 – 1.9mm3 per 106 Cycles). This neither satisfied nor eliminated hypothesis #3, perhaps due to confounding effects, i.e. different designs, MOM diameters and methods. In conclusion, the Inverted test in the simulator appears to offer considerable merit, perhaps analogous to patients who experience edge-wear only intermittently. In contrast the Anatomical test mode appears analogous to patients with mal-positioned cups, who therefore walk on the cup rim constantly throughout their gait Cycle.
Michael J Pappas - One of the best experts on this subject based on the ideXlab platform.
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titanium nitride ceramic film against polyethylene a 48 Million Cycle wear test
Clinical Orthopaedics and Related Research, 1995Co-Authors: Michael J Pappas, G Makris, Frederick F BuechelAbstract:Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce > 40 Million motion Cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37 degrees C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was < 0.02 mm, and < 2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.
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titanium nitride ceramic film against polyethylene a 48 Million Cycle wear test polyethylene wear
Clinical Orthopaedics and Related Research, 1995Co-Authors: Michael J Pappas, G Makris, Frederick F BuechelAbstract:Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce >40 Million motion Cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37° C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was <0.02 mm, and <2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.
G Makris - One of the best experts on this subject based on the ideXlab platform.
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titanium nitride ceramic film against polyethylene a 48 Million Cycle wear test
Clinical Orthopaedics and Related Research, 1995Co-Authors: Michael J Pappas, G Makris, Frederick F BuechelAbstract:Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce > 40 Million motion Cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37 degrees C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was < 0.02 mm, and < 2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.
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titanium nitride ceramic film against polyethylene a 48 Million Cycle wear test polyethylene wear
Clinical Orthopaedics and Related Research, 1995Co-Authors: Michael J Pappas, G Makris, Frederick F BuechelAbstract:Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce >40 Million motion Cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37° C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was <0.02 mm, and <2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.