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Validation of a 3D CT method for measurement of linear wear of acetabular cups: A hip simulator study
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Lund University, Sweden.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
New York University, Department of Radiology.
Loma Linda University, Orthopaedic Research Center.
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2011 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 82, no 1, 35-41 p.Article in journal (Refereed) Published
Abstract [en]

Material and methods Ultra-high molecular weight polyethylene cups with a titanium mesh molded on the outside were subjected to wear using a hip simulator. Before and after wear, they were (1) imaged with a CT scanner using a phantom model device, (2) measured using a coordinate measurement machine (CMM), and (3) weighed. CMM was used as the reference method for measurement of femoral head penetration into the cup and for comparison with CT, and gravimetric measurements were used as a reference for both CT and CMM. Femoral head penetration and wear vector angle were studied. The head diameters were also measured with both CMM and CT. The repeatability of the method proposed was evaluated with two repeated measurements using different positions of the phantom in the CT scanner. Results The accuracy of the 3D CT method for evaluation of linear wear was 0.51 mm and the repeatability was 0.39 mm. Repeatability for wear vector angle was 17 degrees A degrees. Interpretation This study of metal-meshed hip-simulated acetabular cups shows that CT has the capacity for reliable measurement of linear wear of acetabular cups at a clinically relevant level of accuracy.

Place, publisher, year, edition, pages
2011. Vol. 82, no 1, 35-41 p.
Keyword [en]
Total Hip-Arthroplasty, Semiautomated Program, Component Migration, Computed-Tomography, Fusion, Repeatability, Penetration, Time
National Category
Research subject
URN: urn:nbn:se:kth:diva-31654DOI: 10.3109/17453674.2011.552777ISI: 000287025400006PubMedID: 21281259ScopusID: 2-s2.0-79751483254OAI: diva2:405079

QC 20110321

Available from: 2011-03-21 Created: 2011-03-21 Last updated: 2015-06-24Bibliographically approved
In thesis
1. Simulations of Semi-Crystalline Polymers and Polymer Composites in order to predict Electrical, Thermal, Mechanical and Diffusion Properties
Open this publication in new window or tab >>Simulations of Semi-Crystalline Polymers and Polymer Composites in order to predict Electrical, Thermal, Mechanical and Diffusion Properties
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Several novel computer simulation models were developed for predicting electrical, mechanical, thermal and diffusion properties of materials with complex microstructures, such as composites, semi-crystalline polymers and foams.

A Monte Carlo model for simulating solvent diffusion through spherulitic semicrystalline polyethylene was developed. The spherulite model, based on findings by electron microscopy, could mimic polyethylenes with crystallinities up to 64 wt%. Due to the dendritic structure of the spherulites, the diffusion was surprisingly independent of the aspect ratio of the individual crystals. A correlation was found between the geometrical impedance factor (τ) and the average free path length of the penetrant molecules in the amorphous phase. A new relationship was found between volume crystallinity and τ. The equation was confirmed with experimental diffusivity data for Ar, CH4, N2 and n-hexane in polyethylene.

For electrostatics, a novel analytical mixing model was formulated to predict the effective dielectric permittivity of 2- and 3-component composites. Results obtained with the model showed a clearly better agreement with corresponding finite element data than previous models. The analytical 3-component equation was in accordance with experimental data for nanocomposites based on mica/polyimide and epoxy/ hollow glass sphere composites. Two finite element models for composite electrostatics were developed.

It is generally recognized that the fracture toughness and the slow crack growth of semicrystalline polymers depend on the concentrations of tie chains and trapped entanglements bridging adjacent crystal layers in the polymer. A Monte Carlo simulation method for calculating these properties was developed. The simulations revealed that the concentration of trapped entanglements is substantial and probably has a major impact on the stress transfer between crystals. The simulations were in accordance with experimental rubber modulus data.

A finite element model (FEM) including diffusion and heat transfer was developed for determining the concentration of gases/solutes in polymers. As part of the FEM model, two accurate pressure-volume-temperature (PVT) relations were developed. To predict solubility, the current "state of the art" model NELF was improved by including the PVT models and by including chemical interactions using the Hansen solubility parameters. To predict diffusivity, a novel free-volume diffusion model was derived based on group contribution methods. All the models were used without adjustable parameters and gave results in agreement with experimental data, including recent data obtained for polycarbonate and poly(ether-etherketone) pressurized with nitrogen at 67 MPa.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 59 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2012:15
National Category
Polymer Chemistry
urn:nbn:se:kth:diva-93519 (URN)978-91-7501-290-2 (ISBN)
Public defence
2012-04-20, F2,, Lindstedtsvägen 28, entréplan, KTH, Stockholm, 10:00 (English)
QC 20120420Available from: 2012-04-20 Created: 2012-04-20 Last updated: 2012-04-23Bibliographically approved

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