Post-Cam Design Influences the Mechanics and Interface Micromotion of the Tibial Prosthesis Fixation in Posterior-Stabilized Total Knee Arthroplasty: Comparison Among Three Common Designs

Background: Posterior-stabilized prosthesis tibial postloading influences mechanical transfer and micromotion at the tibial prosthesis fixation interface, thereby increasing the risk of prosthesis loosening. However, the effect of different post-cam designs on tibial prosthesis fixation remains unclear. Methods: In this paper, finite element models with and without posts were developed for three common posterior-stabilized prostheses with different post-cam designs (TKA A, B, and C) to investigate the effects of postloading on the von Mises stresses of the proximal tibia, shear stresses of the cement, axial displacement of the tibial tray, and micromotion of the fixation interface under the standing-up-sitting-down and stair descent activities, and to compare the differences in the initial stability of tibial prosthesis fixation under three different post-cam designs. Results: Posterior-stabilized prosthesis postloading significantly increased shear stress of the cement and micromotion of the tibial prosthesis fixation interface at the moment of the maximum flexion angle during the standing-up-sitting-down and stair descent activities. Compared to the TKA A prosthesis with a higher post-cam contact position, the peak fixation interface micromotion of the TKA B prosthesis was reduced by 60.1 and 51.4%, the TKA C prosthesis was reduced by 44.6 and 53.5%, and the postloading interval was significantly smaller for the former. Conclusions: The post-cam design of the posterior-stabilized prosthesis should consider a lower post-cam contact position while avoiding square designs with small spacing between the post and the intercondylar groove of the femoral component and recommending a round post design.