## 4 Results
\[\sigma_{\text{max100}}=\sigma_{\text{max}}\cdot\text{m}\cdot\text{g} \tag{2}\]  
\[\sigma_{\text{max100}}=12.55\times 10^{-2}\times 100\times 9.807=123.08\; \text{MPa} \tag{3}\]  
From the values given in Table 6, Equations (4) and (5) were used to determine the safety coefficient for the elasticity limit state, considering the offset yield strength Rp\({}_{0.2}\) = 800 MPa--see Table 1. The safety values are given in Table 7.  
\[k=\frac{\text{Rp}_{0.2}}{\sigma_{\text{max100}}} \tag{4}\]  
\[k=\frac{800}{123.08}=6.5 \tag{5}\]  
Considering the extreme values, we are operating on the side of safety; the determined stress is far below the material yield strength--see Table 1. Considering the safety coefficients shown in Table 7, we can state that these coefficients are sufficiently high, even when considering maximum values occurring at the notch points (extreme values for the side of safety). It can therefore be stated that all the nails investigated in this study are sufficiently safe and reliable. Limitations of our results are based on examined materials, specific types of implants and our quasistatic approach, i.e., negligence of dynamical effects. Mentioned dynamical effects can be neglected because the patient must stay in bed for a \"short\" time after surgery, which is examined case by case. Similar studies examining femoral nails and dynamic hip screws are presented in [21; 22; 23]. In these references, the results are acquired via numerical approaches and experiments. Similar to our results, the implants are suitable for clinical use. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Nail Material**} & \multirow{2}{*}{**Femur**} & **(HMH)** & \multicolumn{2}{c}{**Medin**} & \multicolumn{2}{c}{**Tantum**} \\ \cline{3-8}  & & _/MPa/_ & **125\({}^{\circ}\)** & **130\({}^{\circ}\)** & **135\({}^{\circ}\)** & **120\({}^{\circ}\)** & **125\({}^{\circ}\)** \\ \hline \multirow{3}{*}{1.4441 steel} & Healed femur & \(\sigma_{e100}\div\sigma_{\text{max100}}\) & 109.35 \(\div\) 123.08 & 55.80 \(\div\) 62.86 & 83.46 \(\div\) 93.95 & 73.16 \(\div\) 82.38 & 80.22 \(\div\) 90.32 \\ \cline{2-8}  & Broken femur & \(\sigma_{e100}\div\sigma_{\text{max100}}\) & 70.81 \(\div\) 79.63 & 54.72 \(\div\) 61.59 & 96.50 \(\div\) 108.56 & 53.45 \(\div\) 60.12 & 83.95 \(\div\) 94.44 \\ \hline \end{tabular}
\end{table} 
Table 6: Stress values at F = 980.7 N. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Nail Material**} & \multirow{2}{*}{**Femur**} & **Safety k/1/** & \multicolumn{2}{c}{**Medin**} & \multicolumn{2}{c}{**Tantum**} \\ \cline{3-8}  & & & **125\({}^{\circ}\)** & **130\({}^{\circ}\)** & **135\({}^{\circ}\)** & **120\({}^{\circ}\)** & **125\({}^{\circ}\)** \\ \hline \multirow{3}{*}{1.4441 steel} & Healed femur & \(k_{e100}\) & 7.32 & 14.34 & 9.59 & 10.93 & 9.97 \\ \cline{2-8}  & & \(k_{max100}\) & 6.50 & 12.73 & 8.52 & 9.71 & 8.86 \\ \cline{1-1} \cline{2-8}  & Broken femur & \(k_{e100}\) & 11.30 & 14.62 & 8.29 & 14.97 & 9.53 \\ \cline{1-1} \cline{2-8}  & & \(k_{max100}\) & 10.05 & 12.99 & 7.37 & 13.31 & 8.47 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Safety coefficients.