Investigating Effects of Testing Parameters on Frictional Heating of UHMWPE by Taguchi Method

Frictional heating makes detrimental effects on surrounding tissue and lubricant around the artificial hip joint. For reduction of this thermal damage, testing parameters and their effects were investigated by using the Taguchi method and analysis of variance. Ultra high molecular weight polyethylene (UHMWPE) acetabular liners and CoCrMo femoral head artificial hip joint components were used as samples. Frictional heating measurements of the joints were carried out on a custom made hip joint friction experimental setup. Surface dimples in different sizes were machined on the inner surface of acetabular insert samples. The tests were conducted under different loading conditions with different testing time. Bovine calf serum was used as lubricant with different amount of third body wear particles in it. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. The experimental results demonstrated that the surface dimples were the major parameter on frictional heating, followed by applied load, amount of third body particles and time. The optimal combination of the testing parameters was predicted and validated by doing experiments

Surface Texturing of Vitamin E Blended UHMWPE for Reduction of Wear

Ultra high molecular weight polyethylene (UHMWPE) has been the most commonly used bearing material in artificial hip and knee replacements. But wear and wear debris of UHMWPE has been the most important problem which cause aseptic loosening and revision surgery of these replacements. For enhangement of wear resistance, new generation UHMWPE materials have been developed and different surface modification techniques have been tried. The objective of this study is to determine the effect of surface dimples on wear behavior of conventional UHMWPE and vitamin E blended UHMWPE (VE-UHMWPE) in ultra-pure water lubrication conditions. Pin-on-disc tribotester was used for measurement of friction coefficient and wear. 0.5 mm in diameter dimples were machined on the surfaces of UHMWPE and VE-UHMWPE discs. CoCrMo pins were used as counter surface. Results were evaluated in terms of materials and presence of dimples

Evaluating Frictional Temperature Rise in Sliding Surface of Artificial Hip Joint Materials with Different Loading Conditions

Friction between articulating surfaces cause temperature rise in acetabular cup and femoral head. This heating may influence the rate of wear, fatigue, creep, oxidative degradation of bearing materials and may terminate surrounding tissue. The objective of this study is to determine temperature rise with different applied load for the articulating surfaces of conventional ultra high molecular weight polyethylene (UHMWPE) and vitamin E blended ultra high molecular weight polyethylene (VE-UHMWPE) acetabular components paired with a ceramic femoral component in bovine calf serum lubrication condition. Additionally frictional torque between the bearing surfaces was measured and friction coefficient was calculated. Frictional measurements of the joints were carried out on a custom made hip joint friction simulator. Various levels of static loads were applied on 28 mm diameter prostheses. In flexion-extension plane, a simple harmonic oscillatory motion between ± 24° was applied to the UHMWPE acetabular component. The period of motion was 1 Hz and the tests were run up to 12,000 cycles. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. The results were compared in terms of UHMWPE and vitamin E blended UHMWPE

Measurement of Wear in Orthopedic Prosthesis

Wear in orthopedic prosthesis has been the main limiting factor of total joint replacement's service life. Wear analysis of total joint replacements is essential for determining failure mechanism, prediction of wear and longevity of implants. So it would be possible to improve design, material and manufacturing quality and service life of these devices. Radiographic, gravimetric, volumetric and optical techniques are current methods for measuring of wear in retrieved implants. Gravimetric method is the standardized method for quantifying wear volumes of total joint prosthesis. Although this method is effective for determining experimental wear volume in simulated conditions, it is not suitable for assessing the clinically retrieved prosthesis for which there is no pre-wear data available. Each of the wear measuring methods has advantages and limitations. Researches have been going on for developing effective methods. In this paper the techniques that are currently used for evaluating wear of orthopedic prosthesis like gravimetry, coordinate measuring machine, micro computed tomography, and digital photogrammetry are explained. The literature works and new trends in metrological assessment of wear are reviewed

Measurement of Wear in Orthopedic Prosthesis

Wear in orthopedic prosthesis has been the main limiting factor of total joint replacement's service life. Wear analysis of total joint replacements is essential for determining failure mechanism, prediction of wear and longevity of implants. So it would be possible to improve design, material and manufacturing quality and service life of these devices. Radiographic, gravimetric, volumetric and optical techniques are current methods for measuring of wear in retrieved implants. Gravimetric method is the standardized method for quantifying wear volumes of total joint prosthesis. Although this method is effective for determining experimental wear volume in simulated conditions, it is not suitable for assessing the clinically retrieved prosthesis for which there is no pre-wear data available. Each of the wear measuring methods has advantages and limitations. Researches have been going on for developing effective methods. In this paper the techniques that are currently used for evaluating wear of orthopedic prosthesis like gravimetry, coordinate measuring machine, micro computed tomography, and digital photogrammetry are explained. The literature works and new trends in metrological assessment of wear are reviewed

Importance of Measurement Parameters for the Dental Implant Surface Characterization

Pure titanium and its alloys have been widely used in biomedical applications on account of their biological and mechanical properties. Although the mechanical properties of titanium provide acceptable responses under dynamic pressures, surface modifications are needed in order to improve osseointegration between bone-implant interfaces. There are many different surface modification techniques like sand blasting, acid etching, or coating with various materials. Surface characterization is as important as surface modification for dental implants. Although many researchers studied about measurement of surface characteristics of dental implants with similar techniques but with different measurement parameters, there is still no consensus about the optimal surface characteristics values of a successful dental implant. Among many other surface characteristics, surface roughness is one of the most important features for dental implants. In this study, the importance of surface roughness measurement of dental implants is discussed and the need of a standardized procedure for implant surface roughness measurement is emphasized. In our experimental study three different processed surfaces as sand blasted and hydrofluoric acid etched surfaces, sand blasted and nitric acid etched surfaces and blasted surfaces were investigated. Results are compared via each method and each processing technique. It is aimed to highlight the importance of a standardized method for measuring and describing surface characteristics. More definitive, standardized methods are needed to augment the rather existing varied combined measurement parameters which affect the results for the assessment of biomedical surfaces

Importance of Measurement Parameters for the Dental Implant Surface Characterization

Pure titanium and its alloys have been widely used in biomedical applications on account of their biological and mechanical properties. Although the mechanical properties of titanium provide acceptable responses under dynamic pressures, surface modifications are needed in order to improve osseointegration between bone-implant interfaces. There are many different surface modification techniques like sand blasting, acid etching, or coating with various materials. Surface characterization is as important as surface modification for dental implants. Although many researchers studied about measurement of surface characteristics of dental implants with similar techniques but with different measurement parameters, there is still no consensus about the optimal surface characteristics values of a successful dental implant. Among many other surface characteristics, surface roughness is one of the most important features for dental implants. In this study, the importance of surface roughness measurement of dental implants is discussed and the need of a standardized procedure for implant surface roughness measurement is emphasized. In our experimental study three different processed surfaces as sand blasted and hydrofluoric acid etched surfaces, sand blasted and nitric acid etched surfaces and blasted surfaces were investigated. Results are compared via each method and each processing technique. It is aimed to highlight the importance of a standardized method for measuring and describing surface characteristics. More definitive, standardized methods are needed to augment the rather existing varied combined measurement parameters which affect the results for the assessment of biomedical surfaces

Migration of a Rigid Mitral Valve Ring

PubMed ID: 19049784[No abstract available

Mid-term results of peripheric cannulation after port-access surgery

PubMed ID: 17846077Several minimally invasive approaches, avoiding median sternotomy, have been described within the last few years for cardiac surgery. Femoral arterial and venous cannulation for extracorporeal perfusion are required for many of these operations. The aim of this report is to assess the long-term outcomes of femoral cannulations in patients who underwent minimally invasive procedures. One hundred and sixty patients underwent operations by the port-access method between January 2002 and October 2006. Cardiopulmonary bypass was established by femoral artery-vein cannulation, and a transthoracic clamp was used for the aortic occlusion. One hundred and twenty-one patients were under follow-up in the outpatient clinic and 85 patients underwent Doppler ultrasonography (US) for femoral arterial and venous stenosis. The mean follow-up was 27.9 months (range 1-57 months). There were three hospital mortalities (1.86%), and five late mortalities in this series. The mean follow-up for the Doppler examination was 20.54 months (range 1-56 months). There were two seromas and three wound complications (2.48%), all of which healed after outpatient treatment. All of the flow patterns of the common femoral arteries (CFA) were triphasic except in three of the patients. Three patients (2.48%) were found to have arterial stenosis. One patient with intermittant claudication underwent percutaneous dilatation and stenting of the CFA. Doppler US detected luminal narrowing in two patients who had been having no symptoms, and they are being followed in the outpatient clinic without any complaints. We found a chronic recanalized thrombotic change in the common femoral vein (CFV) in one patient (0.63%). Our study demonstrates vessel patency and/or stenosis in patients without complaints. In conclusion, femoral artery and vein cannulation for port-access surgery with transthoracic clamping can be performed successfully with excellent results in the mid-term. © 2007 Published by European Association for Cardio-Thoracic Surgery. All rights reserved

SURGICAL PLACEMENT OF LEFT VENTRICULAR LEAD FOR CARDIAC RESYNCHRONIZATION THERAPY AFTER FAILURE OF PERCUTANEOUS ATTEMPTS

WOS: 000317946500175