Effect of total knee replacement conformity design on the displacement, indentation time, contact stress, and strain during impact loading

Abstract

Conformity of contact counterface is one of the important parameters in a total knee replacement (TKR) design. Understanding the effect of conformity on contact stress during static and dynamic loading is crucial. To date, many published reports discussing the effect of conformity were from the static analysis. Therefore, we were compelled to conduct an investigation on the effect of conformity using two-dimensional finite element analysis during dynamic or impact analysis. Five models taken from previous report have been made for this purpose. The model was composed of two parts: femoral indenter and tibial base which represented the femoral component and tibial insert, respectively. A 74 kg was taken as a body mass. The initial impact velocity of 0.6 m/s was applied. The comparative statistical analysis proved that the conformity of TKR significantly (p < 0.05) gave the different effect on the Tresca stress, strain, displacement, indentation time, and also the reaction force. The largest displacement and indentation time of femoral indenter were happened in curved-on-flat model (Rf = 12 mm), and the lowest value was occurred in flat-on-flat (r = 1 mm) model. The largest reaction force was occurred in curved-on-curved model and the lowest one was happened in curved-on-flat (Rf= 12 mm) model. The largest Tresca stress was happened in curved-on-flat (Rf = 12mm) and flat-on-flat (r = 1 mm) model, and the lowest one was occurred in curved-on-flat (Rf = 40mm). The largest strain was occurred in flat-on-flat (r = 1mm) model, and the lowest one was in curved-on-curved model. The curved-on-flat (Rf = 12 mm) model, even though it is bad in displacement, strain, and Tresca value, but it has a good performance in the reaction force value. For the curved-on-flat (Rf= 40 mm) model, it has a good performance if a low Tresca stress design of TKR is needed. The flat-on-flat (r = 1 mm) model, the low displacement and indentation time were its advantage, so that it is suitable for a low wear design of TKR. The flat-on-flat (r = 5 mm) model has no unique performance because all values are high. The last, the curved-on-curved model has the best performance in strain and a moderate good performance in displacement, indentation time, and Tresca value. But, it has a bad performance due to the high value of reaction force. If the average performance owned by each model used, we can summarize that the curved-on-flat (Rf= 12 mm) was the most vulnerable model, and then followed by flat-on-flat (r = 5 mm), flat-on-flat (r = 1 mm), curved-on-curved, and curved-on-flat (Rf= 40 mm) as the safest model.