Biomechanical effects of stem extension of tibial components for medial tibial bone defects in total knee arthroplasty: A finite element study.

The aim of this study was to investigate the biomechanical effects of stem extension with a medial tibial bone defect in primary total knee arthroplasty on load distribution and stress in the proximal tibia using finite element analysis. Finite element simulations were performed on the tibia bone to evaluate the stress and strain on the tibia bone and bone cement. This was done to investigate the stress-shielding effect, stability of tibia plate, and the biomechanical effects in total knee arthroplasty models with various medial defect and different stem length models. The results showed that in the bone defect model, the longer stem, the lower average von Mises stress on the cortical and trabecular bones. In particular, as the bone defect increased, the average von Mises stress on cortical and trabecular bones increased. The average increase in stress according to the size of the bone defect was smaller in the long stem than in the short stem. The maximal principal strain on the trabecular bone occurred mainly at the contact point on the distal end of stem of the tibial implant. When a short stem was applied, the maximal principal strain on the trabecular bone was approximately 8% and 20% smaller than when a long stem was applied or when no stem was applied, respectively. The findings suggest that a short stem extension of the tibial component could help achieve excellent biomechanical results when performing total knee arthroplasty with a medial tibial bone defect.