## 3 Results
The movement of the soft tissue during the process is not controlled by the user. In other words, the changes of the soft tissue depended on the simulation boundary condition. Volumetric changes were observed for soft tissue parts only when the bone part was considered as solid and unchanged. Figure 8 shows the deformation graph of the residuum during the insertion into the MCCT and UCLA socket for both simulations and measurements. The measurement included the deformations of the total soft tissue, fat and muscle. The error bars indicate different volume values for IP and FEA data. The positive and negative values indicate that the volumes respectively increased or decreased during the complete donning process. The correlation coefficient between simulations and measurements remained high. In most cases, fat changes are significant compared to muscle and they mostly contribute to the total soft tissue deformation. In the cases of subjects A and C, the fat and muscle volume decreased in the distal area while they increased in the proximal area in both socket types. However, the fat rapidly changed in the proximal area and corresponded to the enlargement of the muscle. The maximum increase of fat volume occurred in the distal end, whereby during the fitting session, the residuum was theoretically pushed toward the distal end before the socket was vacuumed. The decrease of the volume corresponded to the increase of the residuum length. When the fat was pushed downward, the residuum was shrunk to fit the socket and the total length of the residuum pushed the distal fat. The result supported the assumption that during socket penetration, the residuum tended to shrink to fit the socket shape by pushing the soft tissue downward and thus allowed the length of the residuum to increase. The simulation (FEA) results for subjects A and C indicate that the fat increases in the distal area of the MCCT socket are 18.5% and 23.69%, respectively shown in Figure 8. Additionally, in the distal area of the UCLA socket, the fat respectively increased by 6.63% and 1.68%. However, in the proximal area, the fat respectively decreased by 7.53% and 3.67% in the MCCT socket and by 11.96% and 1.99% in the UCLA socket. Based on the evoked outcomes, we can verify that the fat volume increased in the distal area and decreased in the proximal area of the residuum. The increase of the fat's volume in the distal area led to the increase of the residuum length. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{3}{*}{\(\text{R}^{2}\)} & \multirow{3}{*}{-**Part**} & \multicolumn{3}{c}{A} & \multicolumn{3}{c}{B} & \multicolumn{3}{c}{C} \\ \cline{3-11}  & & NO & MCCT & UCLA & NO & MCCT & UCLA & NO & MCCT & UCLA \\ \cline{2-11}  & Fat & 0.962 & 0.949 & 0.890 & 0.980 & 0.981 & 0.982 & 0.915 & 0.686 & 0.702 \\  & Muscle & 0.994 & 0.968 & 0.965 & 0.979 & 0.982 & 0.980 & 0.987 & 0.977 & 0.994 \\  & Bone & 0.492 & 0.658 & 0.658 & 0.539 & 0.539 & 0.539 & 0.934 & 0.934 & 0.934 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} **Error** \\ **(\%)** \\ \end{tabular} } & \multicolumn{3}{c}{A} & \multicolumn{3}{c}{B} & \multicolumn{3}{c}{C} \\ \cline{3-11}  & & NO & MCCT & UCLA & NO & MCCT & UCLA & NO & MCCT & UCLA \\ \cline{2-11}  & Fat & 2.305 & 0.419 & 2.594 & 2.288 & 0.703 & 0.199 & 0.529 & 0.066 & 3.207 \\  & Muscle & 7.580 & 4.528 & 6.777 & 0.518 & 2.864 & 2.916 & 10.954 & 5.230 & 8.179 \\  & Bone & 0.521 & 0.069 & 0.069 & 0.483 & 0.483 & 0.483 & 1.681 & 1.681 & 1.681 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Correlation coefficient values of residuum volumes for the FEA and IP models and average errors. Figure 7: Heat map of a residuum deformation from anterior cross-section view before and after the donning process.