The interface condition between the prosthesis and the bone tissue must play important roles during dynamic loading transfer through the knee joint. In this study, the three- dimensional impact finite element (FE) simulations were performed to investigate the impact stress propagation.

The FE models of a totally replaced knee joint were constructed with the high shape fidelity. The models included the cortical and cancellous bone, articular cartilage, bone marrow, and the artificial femoral and tibial components. The artificial components were set to the femoral and tibial contact area. The FE meshes had 7251 nodal points and 5547 hexahedral elements (Figure 1).

The interfacial condition between the artificial component had two kind of contact situations, bonding situation and no-bonding ones. In the bonding situation, the interface between the artificial components and the cancellous bone had fully fixations. The no-bonding allowed the tie-breaking of each other although the interface had the high coefficient of friction. The three kind of the impact loading (1, 5, and 10kgW) were applied from the proximal femur to the distal side of tibia.

In the FE simulations, the impact stress propagated to the tibia through the TKR joint components during several milliseconds. On the interfacial surface at the cancellous side of the proximal tibia, the difference in the stress distribution was observed according to the contact situation of the TKR component (Figure 2). The fully fixation (tied to each other) model showed the high compressive stress on the interface. On the other hand, in the no-bonding model, the compressive stress distributed discontinuously and the high compressive stress was observed only in the hole area and edge of the tibial component during the impact loading. In previous research, the cancellous bone had important roles for the load transmission inside the joint especially under the impact loading condition. However, this study indicated that the stress shielding was caused by the imperfect bonding at the interface. More consideration of the interface situation between the bone and component is required to keep stability for impact loading.