## 3 Results  
A total of 463 patients were initially identified. We excluded 123 participants due to the exclusion criteria: 25 because of a double bone cut in surgery and 98 due to osteopororotic pathologies. Thus, 340 patients were finally selected for the analysis. The mean age was 75 \(\pm\) 9.16 years. The majority of the participants were females 262 (77%). There were 167 left knees (49.1%) and 173 right knees (50.9%). In terms of constraint, 322 patients were operated on with the postero-stabilized (PS) system and 18 with the cruciate-retaining (CR) system. No mechanical complications were observed in the present study.  
The mean absolute error of the main variable (the desired angle less the measured angle) for the distal femoral and proximal tibial bone cuts, considering that the observers collected the difference between the planned surgical angle and the real angle observed in X-rays (planned minus real), tended towards varus deviation for both the femoral (1.89\({}^{\circ}\), SD 1.53) and tibial (1.31\({}^{\circ}\), SD 2.54) cuts.  
From at the outliers, it can be observed that 14.7% (50) of the patients had a discrepancy of more than 3\({}^{\circ}\) in the difference between the aimed and real femoral coronal angle, and 18.2% (62) had more than a 3\({}^{\circ}\) difference in the tibial frontal angle.  
No associations were observed between the main variable and the variables of age (divided into three age groups) for either the femur or tibia, gender, laterality, constraint, implant and surgeon (Table 1).  
We did not find any association or correlation between the body mass index (BMI) or preoperative deformity relative to the femoral or tibial cut (Table 2). The interclass correlation coefficient between both observers was 0.599; CI 95% (0.503-0.667).  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & \multicolumn{4}{c}{**Femoral Cut**} & \multicolumn{4}{c}{**Tibial Cut**} \\ \cline{2-10}  & **Group** & \(n\) & **Mean** & **SD** & \(p\)**-Value** & **Group** & \(n\) & **Mean** & **SD** & \(p\)**-Value** \\ \hline \multirow{3}{*}{Age} & \textless{65} & 34 & 1.96 & 1.55 & & \textless{65} & 34 & 0.60 & 2.91 & \\  & 65–79 & 194 & 1.83 & 1.53 & 0.76 & 65–79 & 194 & 1.38 & 2.15 & 0.18 \\  & \textgreater{}79 & 112 & 1.98 & 1.62 & & \textgreater{}79 & 112 & 1.34 & 2.11 & \\ \hline \multirow{3}{*}{Laterality} & Left & 167 & 1.92 & 1.42 & & \textless{167} & 1.10 & 2.18 & \\  & Right & 173 & 1.86 & 1.68 & & Right & 173 & 1.51 & 2.28 & 0.09 \\ \hline \multirow{3}{*}{Gender} & Male & 76 & 1.77 & 1.40 & \textless{16} & Male & 76 & 1.27 & 2.70 & 0.84 \\  & Female & 264 & 1.93 & 1.60 & & Female & 264 & 1.32 & 2.10 & 0.84 \\ \hline \multirow{3}{*}{Constraint} & PS & 322 & 1.90 & 1.55 & & \textless{16} & 0.65 & 322 & 1.31 & 2.25 & 0.81 \\  & CR & 18 & 1.76 & 1.64 & & CR & 18 & 1.44 & 2.09 & 0.81 \\ \hline \multirow{3}{*}{Prosthesis} & NexGen & 60 & 2 & 1.42 & & NexGen & 60 & 1.33 & 2.24 & \\  & Triathlon & 134 & 1.82 & 1.57 & & Triathlon & 134 & 1.30 & 2.15 & 0.48 \\  & U2 & 42 & 1.80 & 1.54 & & U2 & 42 & 1.78 & 2.20 & 0.48 \\  & Genutech & 104 & 1.97 & 1.62 & & Genutech & 104 & 1.13 & 2.37 & \\ \hline \multirow{3}{*}{Surgeon} & 1 & 85 & 1.77 & 1.31 & & 1 & 85 & 1.27 & 2.09 & \\  & 2 & 122 & 1.89 & 1.40 & & 2 & 122 & 1.76 & 2.04 & \\ \cline{1-1}  & 3 & 56 & 1.86 & 1.59 & & 3 & 56 & 1.08 & 1.99 & 0.08 \\ \cline{1-1}  & 4 & 77 & 1.63 & 1.33 & & 4 & 77 & 1.03 & 2.36 & \\ \hline \end{tabular} (SD: standard deviation; \(n\): sample size; PS: postero-stabilized; CR: cruciate-retaining).  
\end{table}
Table 1: Mean deviation in bone cuts considering the variables of age (divided into three age groups), gender, laterality, constraint, implant and surgeon.