Rupesh Ghyar

Effect of Modularity on the Fatigue Performance of Tibial Tray Designs in TKA Prostheses.

Fatigue performance of tibial tray in total knee arthroplasty (TKA) is of critical importance in terms of longevity of the prosthesis. Standards have been proposed by American Society for Testing and Materials (ASTM) and International Organization for Standardization (ISO) to ensure its long-term structural integrity. The aim of the current study is to evaluate the effect of modularity in the tibial tray following the testing standards, using finite element analysis. Goodman and Sines criteria were used to compare the fatigue safety factor (FSF) of four modular designs versus the two conventional designs. Cruciate-retaining (CR) type modular tibial tray designs were better than posterior-stabilized (PS) type tibial tray designs. More cutouts in the tray and absence of keel were reasons for poor fatigue performance.

Comparison of Stresses in Four Modular Total Knee Arthroplasty Prosthesis Designs

The current study, compares the mechanical performance of four modular TKA prostheses based on von Mises stress distribution in the tibial insert. Three-dimensional finite element (FE) models of a cruciate retaining type modular prosthesis and three posterior stabilized (PS) type modular prostheses namely: anterior slide, modular post and double cam, were developed. A compressive load of 2600 N was applied to the FE models at flexion angles of 00, 150, 300, 600 and 900. Von Mises stress was evaluated on all the modular parts of the prostheses and compared with the yield strength of the corresponding material. Von Mises stress in all the parts were below the yield strength of their corresponding material except for tibial insert of anterior slide design at high flexion angle. Von Mises stress above the yield strength in the tibial insert of anterior slide design, was due to edge loading in the post and it demonstrates the likelihood of mechanical failure by delamination type of wear. KEywoRDS Cruciate Retaining, Cruciate Sacrificing, Loosening, Posterior Stabilized, Tibial Post, Total Knee Arthroplasty, UHMWPE, Von Mises Stress