Shunji Hirokawa

Dynamic Finite Element Analysis of Mobile Bearing Type Knee Prosthesis under Deep Flexional Motion

The primary objective of this study is to distinguish between mobile bearing and fixed bearing posterior stabilized knee prostheses in the mechanics performance using the finite element simulation. Quantifying the relative mechanics attributes and survivorship between the mobile bearing and the fixed bearing prosthesis remains in investigation among researchers. In the present study, 3-dimensional computational model of a clinically used mobile bearing PS type knee prosthesis was utilized to develop a finite element and dynamic simulation model. Combination of displacement and force driven knee motion was adapted to simulate a flexion motion from 0° to 135° with neutral, 10°, and 20° internal tibial rotation to represent deep knee bending. Introduction of the secondary moving articulation in the mobile bearing knee prosthesis has been found to maintain relatively low shear stress during deep knee motion with tibial rotation.

Effect of Bearing Mobility on the Kinetics Performance of TKA during Deep Flexion: A Computational Simulation

Characterizing the relative performance between mobile bearing and fixed bearing knee prosthesis remains seen as a difficult task as the previous short-term and mid-term clinical studies disable to observe any evidence of superiority of one design over another. The aim of the present study is to characterize the mechanics comparison between both designs of prosthesis during deep flexional motion with tibial rotation. Three dimensional (3D) FE model of clinically used mobile bearing posterior stabilized (PS) prosthesis was developed from its CAD data. Explicit finite element model was used to simulate the dynamic loaded deep flexional motion from 0 to 135° with neutral and 10° tibial rotation. Fixed bearing prosthesis was represented by fixing the tibial insert to the tibial component. The fixed bearing design was found relatively sensitive to flexion motion and tibial rotation in terms of contact area and maximum shear stress as compared to the mobile bearing design. Tibial rotation increased the peak value of maximum shear stress up to 58 MPa for the fixed bearing, on the contrary, the mobile bearing maintained the peak value of maximum shear stress at 31 MPa even with tibial axial rotation. The influence of post-cam design was also discussed in this study. The mobile bearing has an ability to maintain conformity and relatively low shear stress during very deep flexion with tibial axial rotation in comparison to the fixed bearing.