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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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axis, respectively. The last step was to conduct a surrogate model-based optimization<br />

routine [3] to identify new implant orientations with maximum micromotion lower than<br />

17.38μm. A maximum micromotion of 14μm was found, located posteriorly on the<br />

lateral side (Fig. 6). Future work will validate this result by: (a) using the corresponding<br />

implant orientation angles and offsets as new inputs to ScanIP and +CAD wizards; (b)<br />

simulating the resulting FE model.<br />

Fig. 6: Femur-implant micromotions (mm) resulting from optimum positioning.<br />

5. CONCLUSIONS<br />

A new computational tool is developed that combines Simpleware image processing,<br />

CAD, mesh refinement and scripting capabilities to study the individual or combined<br />

effects of implant orientations. FE meshes of implanted femurs are automatically<br />

generated for contact analysis at the femur-implant interface in THRs and<br />

systematically study the effects of implant positioning on the primary stability of a<br />

cementless implant. More importantly, it gives the analyst the option of pre-defining<br />

and analysing specific implant positions that are likely to affect implant stability or<br />

conduct a DOE to identify the best possible positions in terms of microvement levels.<br />

Therefore, for either the orthopaedist or engineers, the tool can be used to gain an<br />

understanding of the effects of possible differences between the ‘‘achieved’’ and<br />

planned position using for example antero-posterior X-ray images.<br />

6. REFERENCES<br />

1. Karnezis, A., A technique for accurate reproduction of the femoral anteversion<br />

during primary total hip arthroplasty, Architecture Orthopaedic and Traumatologic<br />

Surgery, 2001, Vol. 121, 343-345.<br />

2. Bah, M. T., Nair, P. B., Taylor, M. and Browne, M., Efficient computational method<br />

for assessing the effects of implant positioning in cementless total hip replacements,<br />

J. Biom., 2011, Vol. 44 (7), 1417-1422.<br />

3. Simpleware Ltd., ScanIP, +CAD software version 5.0 reference guide. Exeter, UK,<br />

<strong>2012</strong> (http://www.simpleware.com).<br />

4. Morgan, E. F., Bayraktar, H. H. and Keaveny, T. M., Trabecular bone modulus–<br />

density relationships depend on anatomic site, J. Biom., 2003, Vol. 36 (7), 897-904.<br />

5. Pillar, R.M., Lee, J.M., Maniatopoulos, C., 1986. Observation on the effect of<br />

movement on bone ingrowth into porous-surfaced implants. Clinical Orthopaedics<br />

and Related Research Clin. Orthop. Relat. Res. 20, 108-113.

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