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ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

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segmentation to FE analysis. This computational burden can be eased by applying for<br />

example mesh morphing techniques [2] to automatically generate meshes of the<br />

implanted femur as the implant position varies.<br />

The present work describes a new computational tool specifically designed for multiple<br />

simulations of the effects of hip stem positioning in THRs. New scripting and imagebased<br />

FE modeling capabilities [3] are explored to allow the analyst to conduct a<br />

complete DOE study taking into account possible changes in ante/retroversion,<br />

varus/valgus, anterior/posterior orientations and implant translations. A refined FE mesh<br />

is automatically generated for each pre-defined femur-implant configuration<br />

incorporating assigned mechanical properties, contact pairs, node sets and<br />

boundary/loading conditions required for analysis.<br />

3. MATERIALS AND METHODS<br />

A femur geometry is generated following the segmentation of CT scan images of a 63year<br />

old male patient using ScanIP [3]. It is virtually implanted in the medullary canal in<br />

a neutral nominal position with the Furlong HAC titanium alloy stem (JRI Ltd,<br />

Sheffield, UK) using +CAD [3]. For the automatic generation of multiple implanted<br />

femurs, two wizards are developed. The +CAD wizard starts by defining a local<br />

coordinate system chosen here to be at the implant centroid. A positioning mode<br />

selection is created that allows to pre-define and update a set of implant orientations that<br />

can be read from an excel sheet. Each data field is assigned accordingly to one specific<br />

translation or rotation. Then, the wizard automatically creates new implant positions,<br />

each resulting from fixed values of ante/retroversion, varus/valgus, anterior/posterior<br />

orientation and translations along local axes (Fig. 1).<br />

Fig. 1: Illustration of main steps in +CAD wizard.

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