## 3 Results  
Cyclic tests were conducted and evaluated for all tendons, and S-N curves were computed for individual cadavers and combined overall. The set loads for the tests and the cross-sectional areas were used to calculate the stresses within the tendons. Forces ranged between 200 and 510 N, and the number of cycles between 8 and >260,000. Mean values and standard deviations of specimen average cross-sectional areas; and minimum and maximum values of the axial forces, stress, and cycles-to-failure for each group and pooled data are summarized in Table 1.  
Integrating the number of cycles until failure under different peak stress levels, fatigue diagrams were calculated. Figure 3 exemplifies the subject-dependent S-N curves, which combine the results for the samples from each donor. The number of cycles is displayed on the \(x\)-axis with a logarithmic scale, and the peak stresses on the \(y\)-axis with a linear scale. All three curves yielded a clear tendency towards decreasing stress values for higher numbers of cycles. Individual \(R^{2}\) ranged between 0.54 and 0.88. None of the individual S-N curves yielded \(R^{2}\) values below 0.5. The Woehler curve for the combined results of all tendons can be seen in Figure 4. The \(R^{2}\) for the combined data was 0.65. Material failure was observed in the clamping area for all samples. Failure of the clamps was observed in some of the samples following the mounting. In addition, 38% of the clamps used showed failure patterns after the test, which occurred either during initial clamping or due to cyclic loading of the printed structures. There were four different types of failure--transverse and longitudinal, each either occurring in the middle or the edge of the clamp. Most failures were observed on the edges of the clamps. Out of these failures, 78.3% were longitudinal and 21.7% transverse. Only 0.6% of the clamps failed longitudinally in the central area.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Tissue ID** & \begin{tabular}{c} **0813-5** \\ **(_n_ **= 11)** \\ \end{tabular} & \begin{tabular}{c} **0814-4** \\ **(_n_ **= 9)** \\ \end{tabular} & \begin{tabular}{c} **0801-4** \\ **(_n_ **= 11)** \\ \end{tabular} & \begin{tabular}{c} **0822-4** \\ **(_n_ **= 12)** \\ \end{tabular} & \begin{tabular}{c} **Combined** \\ **(_n_ **= 50 *)** \\ \end{tabular} \\ \hline \begin{tabular}{c} Cross-sectional \\ area (mm\({}^{2}\)) \\ \end{tabular} & 13.42 \(\pm\) 4.21 & 9.85 \(\pm\) 2.09 & 11.16 \(\pm\) 4.72 & 13.22 \(\pm\) 4.69 & 12.04 \(\pm\) 4.40 \\ \hline \begin{tabular}{c} Peak axial force \\ (N) (min-max) \\ \end{tabular} & 250–510 & 250–500 & 200–500 & 240–500 & 200–510 \\ \hline \begin{tabular}{c} Peak stress (MPa) \\ (min-max) \\ \end{tabular} & 17.08–49.59 & 22.31–79.79 & 10.45–88.86 & 11.99–64.66 & 10.45–88.86 \\ \hline \
\begin{tabular}{c} Number of cycles \\ (min–max) \\ \end{tabular} & 16–24,364 & 8–11,744 & 16–261,784 & 32–10,476 & 8–261,784 \\ \hline
\begin{tabular}{c} Coefficient of \\ determination \(R^{2}\) \\ \end{tabular} & 0.84 & 0.68 & 0.88 & 0.54 & 0.65 \\ \hline \end{tabular}
\end{table}
Table 1: Test results of the sample groups’ individual cadavers and combined mean values and standard deviations of the cross-sectional areas, minimum and maximum values of peak axial forces, peak stresses and number of cycles until failure, and coefficient of determination of Woehler curves obtained through power regression. * Individual values of two donors are not given due to a sample size of less than six.  
Figure 3: Subject-dependent S–N curves for tissues obtained from four donor cadavers. Each graph is approximated from the obtained data points using power regression.