The Experts below are selected from a list of 97704 Experts worldwide ranked by ideXlab platform
Youngmin Kwon - One of the best experts on this subject based on the ideXlab platform.
-
sensitivity and specificity of metal ion level in predicting adverse local tissue reactions due to head neck taper corrosion in primary metal on polyethylene total hip arthroplasty
Journal of Arthroplasty, 2018Co-Authors: Youngmin Kwon, John Macauliffe, Paul Arauz, Yun PengAbstract:Abstract Background There is increasing concern regarding the occurrence of adverse local tissue reactions (ALTRs) in metal-on-polyethylene (MoP) total hip arthroplasty (THA) patients due to mechanically assisted crevice corrosion at the head-neck modular taper junction. The utility of metal ion levels in evaluating MoP patients with head-neck taper has not been fully characterized. This study aimed to investigate the sensitivity and specificity of serum metal ions as a predictor of ALTR in MoP THA patients. Methods A total of 62 MoP THA patients in 2 cohorts were investigated: (1) ALTR on metal artifact Reduction Sequence magnetic resonance imaging (n = 43) and (2) without ALTR on metal artifact Reduction Sequence magnetic resonance imaging (n = 19). Receiver-operating characteristic curve was constructed to determine the sensitivity and specificity using different metal ion thresholds and the optimal metal ion cutoff values. Results The presence of ALTR was associated with significantly higher cobalt (8.9 ng/mL vs 0.3 ng/mL, P P P Conclusions Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, serum cobalt level of >1 ng/mL (1 ppb) and Co/Cr ratio >2 thresholds provide evidence-based practical information for surgeons when interpreting metal ion levels in MoP THA patients for clinically relevant head-neck taper corrosion.
-
sensitivity and specificity of metal ion levels in predicting pseudotumors due to taper corrosion in patients with dual taper modular total hip arthroplasty
Journal of Arthroplasty, 2017Co-Authors: Youngmin Kwon, Tsungyuan Tsai, William A Leone, Ming Han Lincoln LiowAbstract:Abstract Background Currently, no serum metal ion threshold exists to identify adverse tissue reactions in total hip arthroplasty (THA) patients with taper corrosion. Our study aims to investigate the sensitivity and specificity of serum metal ions in detecting taper corrosion related pseudotumors in patients with dual taper modular THA. Methods A total of 148 patients with dual taper modular THA were investigated: (1) 90 patients with pseudotumors detected with metal artifact Reduction Sequence-magnetic resonance imaging (MARS-MRI) and (2) 58 patients without pseudotumors on MARS-MRI. Receiver operating characteristic curves were constructed to determine the sensitivity and specificity using different metal ion thresholds. The severity of intraoperative tissue damage was correlated with preoperative metal ion levels. Results Pseudotumor was associated with higher cobalt (5.0 μg/L vs 3.7 μg/L, P P P = .03). Conclusion Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, cobalt level >2.8 μg/L and the Co/Cr ratio >3.8 are useful clinical diagnostic adjuncts in the systematic clinical evaluation for taper corrosion–related adverse tissue reactions in patients with dual modular taper THA.
-
what is the natural history of asymptomatic pseudotumours in metal on metal hip arthroplasty minimum 4 year metal artifact Reduction Sequence magnetic resonance imaging longitudinal study
Journal of Arthroplasty, 2016Co-Authors: Youngmin Kwon, Dimitris Dimitriou, Ming Han Lincoln Liow, Tsungyuan Tsai, Andrew A Freiberg, Harry E RubashAbstract:Abstract Background Metal Artifact Reduction Sequence Magnetic Resonance Imaging (MARS-MRI) is an important cross-sectional imaging modality in detection of metal-on-metal (MoM) hip arthroplasty (HA) pseudotumours. Potential evolution of pseudotumours detected by MARS-MRI in "asymptomatic" patients with MoMHA arthroplasty beyond 2 years remains largely unknown. The aims of this longitudinal study were to (1) determine the natural history of pseudotumours in "asymptomatic" MoMHA patients under MARS-MRI surveillance and (2) characterize MRI feature(s) associated with progressive pseudotumours. Methods A total of 37 MoMHA (32 patients, mean 56 years old) with pseudotumours on MARS-MRI were evaluated longitudinally using a standardized MARS-MRI protocol. Serum cobalt and chromium levels, pseudotumour size, thickness of the cyst wall, and MRI signal intensity of the abnormality were recorded and analyzed. Results At minimum of 4-year follow-up (range 49-54 months), 4 Type II pseudotumours (11%) demonstrated MRI evidence of progression. Five Type I pseudotumours (14%) were found to have "regressed." No measurable MRI progression was detected in remaining patients (75%). MRI features associated with progressive pseudotumours included the presence of increased cystic wall thickness and "atypical" mixed fluid signal. MRI pseudotumour progression was not associated with metal ion levels. Conclusion The natural history of type I cystic pseudotumours continues to be nonprogressive in most "asymptomatic" MoMHA patients at minimum 4 years, suggesting the importance of patient symptoms and MRI characteristic features in the clinical decision-making process. Routine follow-up MARS-MRI evaluation of "asymptomatic" patients with low-grade cystic pseudotumours in the absence of interval clinical changes may not be indicated.
-
is ultrasound as useful as metal artifact Reduction Sequence magnetic resonance imaging in longitudinal surveillance of metal on metal hip arthroplasty patients
Journal of Arthroplasty, 2016Co-Authors: Youngmin Kwon, Dimitris Dimitriou, Ming Han Lincoln Liow, Tsungyuan TsaiAbstract:Abstract Background Current guidelines recommend longitudinal monitoring of at-risk metal-on-metal (MoM) arthroplasty patients with cross-sectional imaging such as metal artifact Reduction Sequence (MARS) magnetic resonance imaging (MRI) or ultrasound. During follow-up evaluations, the clinical focus is on the relative interval changes in symptoms, radiographs, laboratory tests, and cross-sectional imaging modalities. Although MRI has the capacity for the detection of adverse local soft tissue reactions (ALTRs), the potential disadvantages of MARS MRI include the obscuration of periprosthetic tissues by metal artifacts and the cost. The aim of this study was to evaluate the diagnostic accuracy of ultrasound in comparison with MARS MRI in detecting ALTR in MoM patients during consecutive follow-up. Methods Thirty-five MoM patients (42 hips) were recruited prospectively to evaluate the sensitivity and specificity of the ultrasound for detecting ALTR in relation to MARS MRI during 2 longitudinal follow-up scans. The agreement between ultrasound and MARS MRI in ALTR grade, size, and size change was calculated. Results At the initial evaluation and at the subsequent follow-up, ultrasound had a sensitivity of 81% and 86% and a specificity of 92% and 88%, respectively. At the follow-up evaluations, ultrasound was able to detect the "change" in the lesions size with −0.3 cm 2 average bias from the MARS MRI with higher agreement (k = 0.85) with MARS MRI compared to the initial evaluation in detecting any "change" in ALTR size or grade. Conclusion Ultrasound detected the interval change in the ALTR size and grade with higher accuracy and higher agreement with MARS MRI compared with the initial evaluation, suggesting ultrasound is a valid and useful.
-
evaluation of the painful dual taper modular neck stem total hip arthroplasty do they all require revision
Journal of Arthroplasty, 2016Co-Authors: Youngmin KwonAbstract:Although dual taper modular-neck total hip arthroplasty (THA) design with additional neck-stem modularity has the potential to optimize hip biomechanical parameters by facilitating adjustments of leg length, femoral neck version and offset, there is increasing concern regarding this stem design as a result of the growing numbers of adverse local tissue reactions due to fretting and corrosion at the neck-stem taper junction. Implant factors such as taper cone angle, taper surface roughness, taper contact area, modular neck taper metallurgy, and femoral head size play important roles in influencing extent of taper corrosion. There should be a low threshold to conduct a systematic clinical evaluation of patients with dual-taper modular-neck stem THA using systematic risk stratification algorithms as early recognition and diagnosis will ensure prompt and appropriate treatment. Although specialized tests such as metal ion analysis and cross-sectional imaging modalities such as metal artifact Reduction Sequence magnetic resonance imaging (MARS MRI) are useful in optimizing clinical decision-making, overreliance on any single investigative tool in the clinical decision-making process for revision surgery should be avoided.
Tsungyuan Tsai - One of the best experts on this subject based on the ideXlab platform.
-
sensitivity and specificity of metal ion levels in predicting pseudotumors due to taper corrosion in patients with dual taper modular total hip arthroplasty
Journal of Arthroplasty, 2017Co-Authors: Youngmin Kwon, Tsungyuan Tsai, William A Leone, Ming Han Lincoln LiowAbstract:Abstract Background Currently, no serum metal ion threshold exists to identify adverse tissue reactions in total hip arthroplasty (THA) patients with taper corrosion. Our study aims to investigate the sensitivity and specificity of serum metal ions in detecting taper corrosion related pseudotumors in patients with dual taper modular THA. Methods A total of 148 patients with dual taper modular THA were investigated: (1) 90 patients with pseudotumors detected with metal artifact Reduction Sequence-magnetic resonance imaging (MARS-MRI) and (2) 58 patients without pseudotumors on MARS-MRI. Receiver operating characteristic curves were constructed to determine the sensitivity and specificity using different metal ion thresholds. The severity of intraoperative tissue damage was correlated with preoperative metal ion levels. Results Pseudotumor was associated with higher cobalt (5.0 μg/L vs 3.7 μg/L, P P P = .03). Conclusion Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, cobalt level >2.8 μg/L and the Co/Cr ratio >3.8 are useful clinical diagnostic adjuncts in the systematic clinical evaluation for taper corrosion–related adverse tissue reactions in patients with dual modular taper THA.
-
what is the natural history of asymptomatic pseudotumours in metal on metal hip arthroplasty minimum 4 year metal artifact Reduction Sequence magnetic resonance imaging longitudinal study
Journal of Arthroplasty, 2016Co-Authors: Youngmin Kwon, Dimitris Dimitriou, Ming Han Lincoln Liow, Tsungyuan Tsai, Andrew A Freiberg, Harry E RubashAbstract:Abstract Background Metal Artifact Reduction Sequence Magnetic Resonance Imaging (MARS-MRI) is an important cross-sectional imaging modality in detection of metal-on-metal (MoM) hip arthroplasty (HA) pseudotumours. Potential evolution of pseudotumours detected by MARS-MRI in "asymptomatic" patients with MoMHA arthroplasty beyond 2 years remains largely unknown. The aims of this longitudinal study were to (1) determine the natural history of pseudotumours in "asymptomatic" MoMHA patients under MARS-MRI surveillance and (2) characterize MRI feature(s) associated with progressive pseudotumours. Methods A total of 37 MoMHA (32 patients, mean 56 years old) with pseudotumours on MARS-MRI were evaluated longitudinally using a standardized MARS-MRI protocol. Serum cobalt and chromium levels, pseudotumour size, thickness of the cyst wall, and MRI signal intensity of the abnormality were recorded and analyzed. Results At minimum of 4-year follow-up (range 49-54 months), 4 Type II pseudotumours (11%) demonstrated MRI evidence of progression. Five Type I pseudotumours (14%) were found to have "regressed." No measurable MRI progression was detected in remaining patients (75%). MRI features associated with progressive pseudotumours included the presence of increased cystic wall thickness and "atypical" mixed fluid signal. MRI pseudotumour progression was not associated with metal ion levels. Conclusion The natural history of type I cystic pseudotumours continues to be nonprogressive in most "asymptomatic" MoMHA patients at minimum 4 years, suggesting the importance of patient symptoms and MRI characteristic features in the clinical decision-making process. Routine follow-up MARS-MRI evaluation of "asymptomatic" patients with low-grade cystic pseudotumours in the absence of interval clinical changes may not be indicated.
-
is ultrasound as useful as metal artifact Reduction Sequence magnetic resonance imaging in longitudinal surveillance of metal on metal hip arthroplasty patients
Journal of Arthroplasty, 2016Co-Authors: Youngmin Kwon, Dimitris Dimitriou, Ming Han Lincoln Liow, Tsungyuan TsaiAbstract:Abstract Background Current guidelines recommend longitudinal monitoring of at-risk metal-on-metal (MoM) arthroplasty patients with cross-sectional imaging such as metal artifact Reduction Sequence (MARS) magnetic resonance imaging (MRI) or ultrasound. During follow-up evaluations, the clinical focus is on the relative interval changes in symptoms, radiographs, laboratory tests, and cross-sectional imaging modalities. Although MRI has the capacity for the detection of adverse local soft tissue reactions (ALTRs), the potential disadvantages of MARS MRI include the obscuration of periprosthetic tissues by metal artifacts and the cost. The aim of this study was to evaluate the diagnostic accuracy of ultrasound in comparison with MARS MRI in detecting ALTR in MoM patients during consecutive follow-up. Methods Thirty-five MoM patients (42 hips) were recruited prospectively to evaluate the sensitivity and specificity of the ultrasound for detecting ALTR in relation to MARS MRI during 2 longitudinal follow-up scans. The agreement between ultrasound and MARS MRI in ALTR grade, size, and size change was calculated. Results At the initial evaluation and at the subsequent follow-up, ultrasound had a sensitivity of 81% and 86% and a specificity of 92% and 88%, respectively. At the follow-up evaluations, ultrasound was able to detect the "change" in the lesions size with −0.3 cm 2 average bias from the MARS MRI with higher agreement (k = 0.85) with MARS MRI compared to the initial evaluation in detecting any "change" in ALTR size or grade. Conclusion Ultrasound detected the interval change in the ALTR size and grade with higher accuracy and higher agreement with MARS MRI compared with the initial evaluation, suggesting ultrasound is a valid and useful.
Michael P Jennings - One of the best experts on this subject based on the ideXlab platform.
-
formal synthesis of neopeltolide featuring a highly stereoselective oxocarbenium formation Reduction Sequence
ChemInform, 2010Co-Authors: Dionicio Martinezsolorio, Michael P JenningsAbstract:The synthesis of macrolactone (IV) as precursor of unnatural neopeltolide is achieved via allylation of lactone (I) and subsequent stereoselective Reduction of an oxocarbenium compound, generated in situ.
-
formal synthesis of neopeltolide featuring a highly stereoselective oxocarbenium formation Reduction Sequence
Journal of Organic Chemistry, 2010Co-Authors: Dionicio Martinezsolorio, Michael P JenningsAbstract:The formal synthesis of the unnatural (-)-neopeltolide core is discussed in detail. Efficient application of the Evans' protocol for the synthesis of 1,3-syn-diols via an intramolecular hetero-Michael addition followed by reductive deprotection of the resulting benzylidene acetal allowed for swift access to the delta-lactone. Central to the synthetic approach is a tandem nucleophilic addition-diastereoselective axial Reduction of an in situ generated oxocarbenium cation to assemble the beta-C-glycoside moiety of the neopeltolide core.
-
an efficient formal synthesis of clavosolide a featuring a mismatched stereoselective oxocarbenium Reduction
Organic Letters, 2009Co-Authors: Jesse D Carrick, Michael P JenningsAbstract:The enantioselective formal synthesis of the polyketide marine natural product (−)-clavosolide A is presented. The construction of the β-C-glycoside subunit is highlighted by a one-pot oxocarbenium cation formation/Reduction Sequence. Yamaguchi dimerization afforded the diolide aglycon in 18 steps (longest linear Sequence).
Ming Han Lincoln Liow - One of the best experts on this subject based on the ideXlab platform.
-
sensitivity and specificity of metal ion levels in predicting pseudotumors due to taper corrosion in patients with dual taper modular total hip arthroplasty
Journal of Arthroplasty, 2017Co-Authors: Youngmin Kwon, Tsungyuan Tsai, William A Leone, Ming Han Lincoln LiowAbstract:Abstract Background Currently, no serum metal ion threshold exists to identify adverse tissue reactions in total hip arthroplasty (THA) patients with taper corrosion. Our study aims to investigate the sensitivity and specificity of serum metal ions in detecting taper corrosion related pseudotumors in patients with dual taper modular THA. Methods A total of 148 patients with dual taper modular THA were investigated: (1) 90 patients with pseudotumors detected with metal artifact Reduction Sequence-magnetic resonance imaging (MARS-MRI) and (2) 58 patients without pseudotumors on MARS-MRI. Receiver operating characteristic curves were constructed to determine the sensitivity and specificity using different metal ion thresholds. The severity of intraoperative tissue damage was correlated with preoperative metal ion levels. Results Pseudotumor was associated with higher cobalt (5.0 μg/L vs 3.7 μg/L, P P P = .03). Conclusion Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, cobalt level >2.8 μg/L and the Co/Cr ratio >3.8 are useful clinical diagnostic adjuncts in the systematic clinical evaluation for taper corrosion–related adverse tissue reactions in patients with dual modular taper THA.
-
what is the natural history of asymptomatic pseudotumours in metal on metal hip arthroplasty minimum 4 year metal artifact Reduction Sequence magnetic resonance imaging longitudinal study
Journal of Arthroplasty, 2016Co-Authors: Youngmin Kwon, Dimitris Dimitriou, Ming Han Lincoln Liow, Tsungyuan Tsai, Andrew A Freiberg, Harry E RubashAbstract:Abstract Background Metal Artifact Reduction Sequence Magnetic Resonance Imaging (MARS-MRI) is an important cross-sectional imaging modality in detection of metal-on-metal (MoM) hip arthroplasty (HA) pseudotumours. Potential evolution of pseudotumours detected by MARS-MRI in "asymptomatic" patients with MoMHA arthroplasty beyond 2 years remains largely unknown. The aims of this longitudinal study were to (1) determine the natural history of pseudotumours in "asymptomatic" MoMHA patients under MARS-MRI surveillance and (2) characterize MRI feature(s) associated with progressive pseudotumours. Methods A total of 37 MoMHA (32 patients, mean 56 years old) with pseudotumours on MARS-MRI were evaluated longitudinally using a standardized MARS-MRI protocol. Serum cobalt and chromium levels, pseudotumour size, thickness of the cyst wall, and MRI signal intensity of the abnormality were recorded and analyzed. Results At minimum of 4-year follow-up (range 49-54 months), 4 Type II pseudotumours (11%) demonstrated MRI evidence of progression. Five Type I pseudotumours (14%) were found to have "regressed." No measurable MRI progression was detected in remaining patients (75%). MRI features associated with progressive pseudotumours included the presence of increased cystic wall thickness and "atypical" mixed fluid signal. MRI pseudotumour progression was not associated with metal ion levels. Conclusion The natural history of type I cystic pseudotumours continues to be nonprogressive in most "asymptomatic" MoMHA patients at minimum 4 years, suggesting the importance of patient symptoms and MRI characteristic features in the clinical decision-making process. Routine follow-up MARS-MRI evaluation of "asymptomatic" patients with low-grade cystic pseudotumours in the absence of interval clinical changes may not be indicated.
-
is ultrasound as useful as metal artifact Reduction Sequence magnetic resonance imaging in longitudinal surveillance of metal on metal hip arthroplasty patients
Journal of Arthroplasty, 2016Co-Authors: Youngmin Kwon, Dimitris Dimitriou, Ming Han Lincoln Liow, Tsungyuan TsaiAbstract:Abstract Background Current guidelines recommend longitudinal monitoring of at-risk metal-on-metal (MoM) arthroplasty patients with cross-sectional imaging such as metal artifact Reduction Sequence (MARS) magnetic resonance imaging (MRI) or ultrasound. During follow-up evaluations, the clinical focus is on the relative interval changes in symptoms, radiographs, laboratory tests, and cross-sectional imaging modalities. Although MRI has the capacity for the detection of adverse local soft tissue reactions (ALTRs), the potential disadvantages of MARS MRI include the obscuration of periprosthetic tissues by metal artifacts and the cost. The aim of this study was to evaluate the diagnostic accuracy of ultrasound in comparison with MARS MRI in detecting ALTR in MoM patients during consecutive follow-up. Methods Thirty-five MoM patients (42 hips) were recruited prospectively to evaluate the sensitivity and specificity of the ultrasound for detecting ALTR in relation to MARS MRI during 2 longitudinal follow-up scans. The agreement between ultrasound and MARS MRI in ALTR grade, size, and size change was calculated. Results At the initial evaluation and at the subsequent follow-up, ultrasound had a sensitivity of 81% and 86% and a specificity of 92% and 88%, respectively. At the follow-up evaluations, ultrasound was able to detect the "change" in the lesions size with −0.3 cm 2 average bias from the MARS MRI with higher agreement (k = 0.85) with MARS MRI compared to the initial evaluation in detecting any "change" in ALTR size or grade. Conclusion Ultrasound detected the interval change in the ALTR size and grade with higher accuracy and higher agreement with MARS MRI compared with the initial evaluation, suggesting ultrasound is a valid and useful.
Mark Lautens - One of the best experts on this subject based on the ideXlab platform.
-
palladium catalyzed reductive ortho arylation evidence for the decomposition of 1 2 dimethoxyethane and subsequent arylpalladium ii Reduction
Organic Letters, 2010Co-Authors: Andrew Martins, David A Candito, Mark LautensAbstract:A palladium-catalyzed crossed biaryl coupling/Reduction Sequence enables the formation of meta-substituted biaryls via solvent-mediated arylpalladium(II) Reduction. Isotope labeling studies determined that the decomposition of 1,2-dimethoxyethane (DME) is indeed involved in the reductive process.
-
palladium catalyzed reductive ortho arylation evidence for the decomposition of 1 2 dimethoxyethane and subsequent arylpalladium ii Reduction
Organic Letters, 2010Co-Authors: Andrew Martins, David A Candito, Mark LautensAbstract:A palladium-catalyzed crossed biaryl coupling/Reduction Sequence enables the formation of meta-substituted biaryls via solvent-mediated arylpalladium(II) Reduction. Isotope labeling studies determined that the decomposition of 1,2-dimethoxyethane (DME) is indeed involved in the reductive process.
