Finite Element Analysis of the Proximal implanted Tibea in relation to implant loosening

Abstract

Tibial component alignment is one of the parameters that have most influence on implant loosening. The effect of varus-valgus and antero-posterior angles on the cancellous bone stress at the bone-implant interface was examined by means of finite element analysis. The lowest stress was obtained when the tibial tray was orientated in values. Moreover, the larger the valgus tilt was, the lower were the stresses within the cancellous bone. It was observed that higher stresses were produced with a posterior angle, as compared to a perfectly horizontal tibial cut. These findings were in line with clinical observations related to prosthesis orientations.

In general, previously reported finite element models did not include patient specific data. Therefore, a comprehensive convergence study was performed in order to determine the finite element mesh characteristics (element size) and material property distribution (number of material groups) necessary to accurately describe the stress and risk ratio distributions at the bone-implant interface in patient-specific FE models. It was observed that with a logarithmic discretisation of the material properties within the bone convergence was reached with fewer material groups, as compared to the linear discretisation. Convergence was assessed at two levels, locally be examining variations at the nodal points and globally, by examining the mean and peak values within a pre-defined volume. This study has shown that accurate assignment of the material properties is critical in achieving convergence of other parameters such as stress and risk ratio. If convergence of the assigned material properties is not achieved, errors are then propagated through to other parameters of interest. There has been found no evidence of previous studies that show that the assigned material properties in models of bony structures are influenced by the mesh density, as was demonstrated here.

In the final part of the thesis, based on the convergence study, a combined, prospective FE and RSA migration study was performed.

More information

Identifiers

Catalogue record

Export record

ASCII CitationAtomBibTeXData Cite XMLDublin CoreDublin CoreEP3 XMLEndNoteHTML CitationHTML CitationHTML ListJSONMETSMODSMPEG-21 DIDLOpenURL ContextObjectOpenURL ContextObject in SpanRDF+N-TriplesRDF+N3RDF+XMLRIOXX2 XMLReferReference ManagerSimple Metadata