## 4 Discussion  
While most patients undergoing TKA are satisfied with the outcome, about a quarter of the patients remain dissatisfied, to varying degrees, even in the absence of a complication. Several factors may be involved, including inappropriate indications, a lack of preoperative information, and surgical factors such as implant alignment, ligament balance or post-operative complications. The positioning of the prosthesis is a determining factor in the medium- and long-term results [1,2], which is why technological progress has focused on tools that allow personalized and reproducible positioning. Accelerometers are part of the range of tools available to optimize positioning or at least make it more reproducible. The aim of this study was to evaluate the accuracy of the Perseus System for making the tibial cut on TKA, to determine if this technique is safe and reproducible. Analysis of the primary endpoint showed that the tibial cut navigated by the Perseus accelerometer had a significant tendency to varus of 1.5\({}^{\circ}\) compared with the control group. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Perseus Group (\(n=20\))**} & \multicolumn{4}{c}{**Control Group (\(n=40\))**} \\ \hline  & **N** & **(\%)** & **Mean \(\pm\) SD** & **Median** & **Miz; Max** & **N** & **(\%)** & **Mean \(\pm\) SD** & **Median** & **Miz; Max** \\ \hline \multicolumn{2}{c}{**Radiological analysis (\({}^{\circ}\))**} & & & & & & & & & \\  & TMA & & 87.6 \(\pm\) 2.1 & 87.5 & (84.0; 91.0) & & 89.1 \(\pm\) 1.6 & 89.5 & (84.0; 92.0) & 0.009 \\  & IS & & 90.0 \(\pm\) 1.9 & 90.0 & (86.0; 94.0) & & 89.9 \(\pm\) 1.3 & 90.0 & (86.0; 93.0) & 0.958 \\  & HKA & & & 177.7 \(\pm\) 1.8 & 177.5 & (175.0; 181.0) & & 177.5 \(\pm\) 2.2 & 178.0 & (171.0; 181.0) & 0.744 \\  & FMA & & & 89.9 \(\pm\) 1.9 & 90.0 & (87.0; 94.0) & & 88.9 \(\pm\) 1.6 & 89.0 & (85.0; 92.0) & 0.037 \\  & TMA & 3 & (15.0\%) & & & 3 & (7.5\%) & & 0.412 \\  & TS & 2 & (10.0\%) & & & 2 & (5.0\%) & & 0.602 \\  & HKA & 3 & (15.0\%) & & & 10 & (25.0\%) & & 0.742 \\  & FMA & 1 & (5.0\%) & & & 3 & (7.5\%) & & 0.946 \\ \hline  & & & & & & & & & \\ \multicolumn{2}{c}{} & & & & & & & & & \\ \multicolumn{2}{c}{} & & & & & & & & & \\ \multicolumn{2}{c}{} & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Post-operative results. Figure 3: TMA comparison chart. On the other hand, accelerometer navigation allowed a satisfying restitution of the tibial slope in the sagittal plane, but without being superior to the conventional instrumentation. Accelerometer navigation was not more accurate than conventional instrumentation for the tibial cut in this study. The studies in the literature are not consistent as to whether accelerometers improve the tibial cut's accuracy. Several accelerometer systems are available and assessed in the literature. Due to a potential disparity, an independent assessment of every accelerometer system seems more appropriate. [PERSON] et al. and [PERSON] et al. respectively found satisfying results with TMA values of 90.1 \(\pm\) 1.4\({}^{\circ}\) and 89.8 \(\pm\) 1.4\({}^{\circ}\) in the accelerometer groups, compared with 89.6 \(\pm\) 1.3\({}^{\circ}\) and 90.1 \(\pm\) 1.4\({}^{\circ}\) in the groups with conventional instrumentation, with no significant difference [18,19], as did [PERSON] et al. [13]. Several studies reported a valgus deviation of the tibial cut (range from 0.4\({}^{\circ}\) to 1.3\({}^{\circ}\)) [20, 21, 22]. Conversely, [PERSON] et al. and [PERSON] et al. found a varus cut of 0.55 \(\pm\) 0.43\({}^{\circ}\) and 0.77 \(\pm\) 0.64\({}^{\circ}\), respectively [23,24]. This study also reported a varus deviation of the tibial cut in a population with preoperative varus deformity. This kind of deviation had fewer consequences for the implant survival, theoretically, because this deviation remained inferior to 3\({}^{\circ}\) and was in the same deformity as preoperatively. Most studies found no difference in tibial slope from conventional instrumentation [21, 22, 23].