## 3 Results
### Custom-Made Implant 2  
A biomechanical test on the taper junction of reference implant 2 showed that the assembly withstood cyclic loading, with a peak load of 2.3 kN for 5,000,000 cycles and thereby, fulfilled the pre-defined acceptance criterion [30]. A stepwise increase in the peak load by 500 N after completion of each 1,000,000 cycles showed no macroscopic damage to the taper junction. The procedure was stopped after completion of load step 4.8 kN. Since the taper junction was applied to a knee implant, the simulated load level of the custom-made implant was 2.7 kN. In both FEAs, the screw pre-tension values were assumed to be 5 kN, 6.5 kN and 8 kN. Obtained values of tensile stress, van Mises stress and micromotion were compared between reference implant 2 and custom-made implant 2, in terms of absolute values and relative values (Table 3). The values for maximum micromotion, as the main failure mechanism, were lower in custom-made implant 2 compared to reference implant 2. Depending on the screw pre-tension, the relative values of maximum micromotion of custom-made implant 2 were 91%, 87%, and 82% compared to reference implant 2. The values for maximum tensile stress and maximum van Mises stress were higher in custom-made implant 2 compared to reference implant 2 and were in a range between 120% and 127%. The micromotion distributions were similar between reference implant 2 and custom-made implant 2 (Figure 6). The locations of the maximum values in both implants are at the bottom of the taper junction, in the direction of the fixation screw, on the side where the loads were applied. During load application, the taper junction gets compressed, whereby, at the load side, more micromotion was observed. Yet, maximum \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Max. Tensile Stress [MPa]**} & \multicolumn{3}{c}{**Max. Van Mises Stress [MPa]**} & \multicolumn{3}{c}{**Max. Micromotion [mm]**} \\ \hline
**Screw Tension** & **5 kN** & **6.5 kN** & **8 kN** & **5 kN** & **6.5 kN** & **8 kN** & **5 kN** & **6.5 kN** & **8 kN** \\ \hline Reference & 551 & 660 & 772 & 571 & 637 & 731 & 0.0247 & 0.0237 & 0.0227 \\ implant & 100\% & 100\% & 100\% & 100\% & 100\% & 100\% & 100\% & 100\% \\ Custom-made & 697 & 818 & 940 & 687 & 807 & 927 & 0.0225 & 0.0206 & 0.0187 \\ implant & 126\% & 124\% & 121\% & 120\% & 126\% & 127\% & 91\% & 87\% & 82\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: FEA results of custom-made implant 2. Figure 5: Experimental results of custom-made implant 1. (**a**) Load and displacement curves relative to cycles. (**b**) Mechanical fracture of one sample of reference implant 1. (**c**) Fracture of the stem connected to custom-made implant 1.  
micromotion values of 0.0237 mm and 0.0206 mm are small and in a range where only negligible fretting corrosion would be expected. The micromotion distribution of custom-made implant 2 showed a similar pattern compared to the tested taper junction (Figure 7c). The areas of contact were visible with a characteristic pattern of moderate fretting corrosion, yet no severe macroscopic fretting corrosion damage could be observed. The FEA results of custom-made implant 2 were also verified in a biomechanical test. The test showed that the assembly withstood cyclic loading with a peak load of 2.7 kN for 10,000,000 cycles without failure and thereby, fulfilled the required acceptance criterion. A stepwise increase of 500 N after completion of each 1,000,000 cycles showed no macroscopic failure in the taper junction (Figure 7b). The procedure was stopped after completion of load step 4.7 kN (Figure 7a). Figure 6: FEA results of reference implant 2 and custom-made implant 2. (**a**) Maximum micromotion (d\({}_{\text{max}}\)) and micromotion distribution of reference implant 2 and (**b**) custom-made implant 2. Figure 7: Experimental results of custom-made implant 2. (**a**) Load and displacement relative to cycles. (**b**) Components of custom-made implant 2 test assembly.