Load Transfer Analysis at the Interface Between a Steel Post and Polyethylene Matrix Using Pull-Out Test: Experimental and Theoretical Parametric Study

In various kinds of orthopedic or dental prostheses, adequate fixation of prosthetic components to the host bone represents a great challenge. The short- and long-term fixation stabilities of the implants are often provided by the use of posts. In this work, a cylindrical steel post inserted in a predrilled High Density Polyethylene (HDPE) cylinder with an initial interference fit was used as a model to analyze the contribution of post fixation to the initial stability of Total Knee Arthroplasty (TKA) tibial component. To characterize the ability of the steel post/HDPE cylinder interface for transferring mechanical load, pull-out tests were carried out on the model post fixation for different initial interference fits and implantation lengths. Experimental ultimate pull-out force was found to increase in a quasi-linear fashion with increase in the interference fit or the implantation length. On the basis of Coulomb friction at the post/HDPE interface, an analytical model has been developed for the analysis of the experimental ultimate pull-out force results. For the ranges of initial interference fit and implantation length considered, the analytical model was fitted to the experimental results by adjusting the friction coefficient. The mean value of the friction coefficient obtained was 0.043. Finite element simulation was also carried out for the pull-out test using the ABAQUS program. It was found that the finite element simulation describes well the experimental ultimate pull-out forces than the analytical calculation. (C) Koninklijke Brill NV, Leiden, 2009