Comparison of tibial fixations in total knee arthroplasty: an evaluation of stress distribution and interface micromotions

Abstract

A three-dimensional finite element model was developed for evaluating tibial component fixations in total knee replacement. The effects of varus misalignment in the frontal plane and of anterior shear forces in the sagittal plane on global displacements, relative micromotions and interface stress distribution were investigated. The anisotropic elastic-plastic behaviour of bone and the discontinuity at the bone-implant interface were taken into account. The model was applied on cemented metal tray total condylar (MTTC) and on uncemented porous coated anatomical (PCA) tibial plateaus. It was observed that displacements, micromotions and stress transfer at the interface depended considerably on the tibial anchorage design. The MTTC plateau was supported mainly on the internal and external cortical shell while the PCA plateau was supported more on the anterior and posterior zones. In the spongious bone, stress magnitude under the MTTC plateau increased from the central region to the periphery, while for the PCA plateau the most stressed regions were those around the pegs. Analysis of displacements shows that the MTTC plateau mainly rotated around the tibial axis, while the PCA plateau motion was mainly a rotation combined with a plateau bending around the medial-lateral axis