## 3 Results
### Analysis of Variance  
#### 3.2.1 Two Locking Screws  
The maximum principal stress of two locking screws results from running the FEA model at various testing conditions, as shown in Table 7. All main factors were identified in importance by the analysis of variance (ANOVA) shown in Table 8. Furthermore, R-squared and adjusted R-squared statistics were analyzed for checking the fit of the dataset. Moreover, if the p-value of each main effect and its interaction was less than 0.05, it was considered statistically significant. According to this analysis, gap type (A), fracture gap (B), fixation techniques (D), the interaction between the variables A and D, and the interaction between the variables A and B were factors that affected the maximum principal stress of the composite interlocking nail. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & \multirow{2}{*}{**A**} & \multirow{2}{*}{**B**} & \multirow{2}{*}{**C**} & \multirow{2}{*}{**D**} & \multicolumn{2}{c}{**Principal**} & \multirow{2}{*}{**Condition**} & \multirow{2}{*}{**A**} & \multirow{2}{*}{**B**} & \multirow{2}{*}{**C**} & \multirow{2}{*}{**D**} & \multicolumn{1}{c}{\multirow{2}{*}{**Principal**}} \\  & & & & & & & & & & & & **Stress** \\ \hline  
& 43.41 & 122 & Distal & 1 & 160 & 2D & 131.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: FEA model of the two locking screws’ results for the testing conditions. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Condition** & **A** & **B** & **C** & **D** & \
\begin{tabular}{c} **Principal** \\ **Stress** \\ \end{tabular} & **Condition** & **A** & **B** & **C** & **D** &
\begin{tabular}{c} **Principal** \\ **Stress** \\ \end{tabular} \\ \hline  
& 129.35 & 154 & Distal & 3 & 140 & P-D & 125.09 \\  & & & & & & 155 & Distal & 3 & 140 & P-M & 218.22 \\  & & & & & & 156 & Distal & 3 & 140 & M-D & 104.35 \\  & & & & & & 157 & Distal & 3 & 160 & 2P & 283.41 \\  & & & & & & 158 & Distal & 3 & 160 & 2D & 164.47 \\  & & & & & & 159 & Distal & 3 & 160 & 2M & 249.58 \\  & & & & & & 160 & Distal & 3 & 160 & P-D & 128.83 \\  & & & & & & 161 & Distal & 3 & 160 & P-M & 315.93 \\  & & & & & & 162 & Distal & 3 & 160 & M-D & 112.42 \\ \hline \hline \end{tabular}  
* According to orthopedic veterinary surgeons, this condition could not be treated by locking screws in that position because the locking screws could not be locked near the fracture site of the middle shaft fracture.  
\end{table} 
Table 7: _Cont._ \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Source** & **DF** & **Adj. SS** & **Adj. MS** & **\(F\)-Value** & **\(P\)-Value** \\ \hline Model & 23 & 505,293 & 21,969.3 & 26.18 & 0.000 \\ Linear & 9 & 230,383 & 25,598.1 & 30.51 & 0.000 \\ A & 2 & 151,544 & 75,772.0 & 90.30 & 0.000 \\ B & 2 & 34,878 & 17,439.0 & 20.78 & 0.000 \\ D & 5 & 23,384 & 4676.7 & 5.57 & 0.000 \\ Z-Way Interactions & 14 & 127,635 & 9116.8 & 10.86 & 0.000 \\ A*B & 4 & 24,258 & 6064.4 & 7.23 & 0.000 \\ A*D & 10 & 100,187 & 10,018.7 & 11.94 & 0.000 \\ \hline Error & 115 & 96,498 & 839.1 & \\ \hline Total & 138 & 601,791 & & & & \\ \hline \hline \end{tabular}  
* R-Square = 83.96\(\%\), R-Square (adj.) = 80.76\(\%\).  
\end{table} 
Table 8: Analysis of variance (ANOVA) for principal stress (two locking screws). The R\({}^{2}\) value shows that the model explains 83.96% of the variance in the maximum principal stress, which indicates that the model fits the data well. The residual plot of the maximum principal stress is shown in Figure 7, representing the normal probability plot of the residuals. The residuals of the response randomly scatter around zero in the residual plots. Regarding the residuals versus the fits, the observation points (blue dots) scattered randomly in the normal probability plot show that the process parameters in this study were normal and independently distributed. The histogram of the residuals is approximately symmetric. Regarding the residuals versus the order, the residuals exhibit no clear pattern.