Experimental validation of numerically predicted strain and micromotion in intact and implanted composite hemi-pelvises.

The failure mechanisms of acetabular prostheses may be investigated by understanding the changes in load transfer due to implantation and using the analysis of the implant-bone micromotion. Computational finite element (FE) models allow detailed mechanical analysis of the implant-bone structure, but their validity must be assessed as a first step, before they can be employed in preclinical investigations. In this study, FE models of composite hemi-pelvises, intact and implanted with an acetabular cup, were experimentally validated. Strains and implant-bone micromotions in the hemi-pelvises were compared with those predicted by the equivalent FE models. Regression analysis indicated close agreement between the measured and FE strains, with a high correlation coefficient (0.95-0.98), a low standard error (SE) (36-53 mu epsilon) and a low error in regression slope (7%-11%). Measured micromotions along three orthogonal directions were small, less than 30 microm, whereas the FE-predicted values were found to be less than 85 .m. Although the trends were similar, the deviations are due to artefacts in experimental measurement and additional imperfections in recreating experimental loading and boundary conditions in the FE model. This supports the FE model as a valid predictor of the measured strain in the composite pelvis models, confirming its suitability for further computational investigations on acetabular prostheses.