Biomechanical effect of anatomical tibial component design on stress shielding of medial proximal tibial bone in total knee arthroplasty: finite element analysis of 30 Korean models

Abstract

Purpose This study aimed to identify the effect of anatomical tibial component (ATC) design on stress distribution in the proximal tibia of Koreans using finite element analysis (FEA). Materials and Methods Three-dimensional (3D) finite element models of 30 tibias were created using modified tetrahedral ten-node elements. A symmetric tibial component (STC, NexGen LPS-Flex) and an ATC (Persona) were used in surgical simulation. We compared the FEA measurements (stress and strain) around the stem tip and in the medial half of the proximal tibial bone, as well as the distance from the distal stem tip to the shortest anteromedial cortical bone. Then, correlations between this distance and FEA measurements were analyzed. Results The distance from the distal stem tip to the shortest cortical bone showed no statistically significant difference between implants. However, the peak von Mises stress around the distal stem tip was higher with STC than with ATC. In the medial half of the proximal tibial bone, the peak von Mises stress showed no statistical difference between two implants; but the average von Mises stress, maximum principal strain, and minimum principal strain were higher with ATC. Both implants showed a negative correlation between the distance and peak stress around the distal stem tip. In the medial half of the proximal tibial bone, ATC showed a positive correlation between the distance and average von Mises stress and a negative correlation between the distance and average minimum principal strain. STC showed no correlation between the distance and average values in the medial half of the proximal tibial bone. Conclusion Implant design, including the medialized stem and the anatomic shape of the baseplate, affects the distribution of stress and strain on the proximal tibia. In Korean women, the medialized stem of ATC does not come closer to the cortical bone and transmits more stress and strain to the proximal tibial bone than STC does. However, unlike STC, the shorter the distance between the stem and the anteromedial cortical bone, the less stress and strain applied to the medial proximal cutting plane in ATC. Therefore, when using ATC, stress shielding should be considered in patients with severe anatomical variations or in cases of surgical error.