Probabilistic finite element analysis of the uncemented total hip replacement

Abstract

There are many interacting factors affecting the performance of a total hip replacement(THR), such as prosthesis design and material properties, applied loads, surgical approach, femur size and quality, interface conditions etc. All these factors are subject to variation and therefore uncertainties have to be taken into account when designing and analysing the performance of these systems. To address this problem, probabilistic design methods have been developed.
A computational probabilistic tool to analyse the performance of an uncemented THR has been developed. Monte Carlo Simulation (MCS) was applied to various models with increasing complexity. In the pilot models, MCS was applied to a simplified finite element model (FE) of an uncemented total hip replacement (UTHR). The implant and bone stiffness, load magnitude and geometry, and implant version angle were included as random variables and a reliable strain-based performance indicator was adopted. The sensitivity results highlighted the bone stiffness, implant version and load magnitude as the most sensitive parameters.The FE model was developed further to include the main muscle forces, and to consider fully bonded and frictional interface conditions. Three proximal femurs and two implants (one with a short and another with a long stem) were analysed. Different boundary conditions were compared, and convergence was improved when the distal portion of the implant was constrained and a frictional interface was employed. This was particularly true when looking at the maximum nodal micromotion. The micromotion results compared well with previous studies, confirming the reliability and accuracy of the probabilistic finite element model (PFEM). Results were often influenced by the bone, suggesting that variability in bone features should be included in any probabilistic analysis of the implanted construct.
This study achieved the aim of developing a probabilistic finite element tool for the analysis of finite element models of uncemented hip replacements and forms a good basis for probabilistic models of constructs subject to implant position-related variability.

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ORCID for M. Browne: orcid.org/0000-0001-5184-050X

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