Effect of post-cam design on the kinematics and contact stress of posterior-stabilized total knee arthroplasty

BACKGROUND: The post-cam mechanism in the posterior-stabilized (PS) implant plays an important role, such as durability and kinematic performances, in total knee arthroplasty (TKA). OBJECTIVE: The purpose of this study was to evaluate the difference in the kinematics and contact stress of five post-cam designs, which are flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs, using three-dimensional finite element models. METHODS: We designed the post-cam model with five different geometries. The kinematics, contact stress, and contact area were evaluated in the five post-cam designs under gait cycle loading conditions using the finite element method. RESULTS: There were no differences in the contact stress and area on the tibial insert in all designs. The largest internal rotation was shown in the swing phase for the helical design, and the largest tibial posterior translation was observed for the curve-and-curve (concave) design. The curve-and-curve (concave) design showed the lowest contact stress and the largest posterior tibial translation during the gait cycle. CONCLUSIONS: Considering the kinematics and contact stress, we found that the curve-and-curve (concave) design was more stable than other designs. From the results, we found the important factors of TKA implant considering stability and kinematics.