## 4 Discussion
However, some authors reported a moderate increase in the tibial slope of 0.5\({}^{\circ}\) to 1\({}^{\circ}\) on average [20,24]. The accelerometer system assessed in this study accurately reproduced the tibial slope with no significant difference from conventional instrumentation. More than the comparison of mean angle values, the rate of outliers is an interesting indicator of a surgical technique's reproducibility and reliability. In this study, the mean frontal deviation in the accelerometer group was inferior to the 3\({}^{\circ}\) margin of error. These results were similar to those in the literature [13,15,18]. However, the rate of outliers for the frontal axis of the tibial cut was not low (15%). The lack of significant difference between both groups for the outliers' rate could be secondary to the small size of the groups in this study. The literature seems to be unequivocal on the outliers' rate with accelerometer navigation, showing a significant reduction of the outliers' rate [25, 26, 27], particularly for the mechanical femoral angle (FMA) [18,28]. In a randomized controlled trial involving 100 patients, where 50 were operated on with accelerometer navigation, [PERSON] et al. found a proportion of outliers of 9% in the accelerometer group vs. 27% in the control group for the TMA, and 31% vs. 49% respectively for the HKA [29]. [PERSON] et al. found 3% of outliers with FMA with accelerometer system versus 15% with conventional instrumentation, with no difference with TMA in a retrospective study of 159 TKAs [18]. In addition, [PERSON] et al. in a recent systematic review of randomized controlled trials, found less outliers with mechanical alignment (relative risk increase of 38% to be an outlier on HKA with conventional technique) [11]. The improvement in clinical results due to accelerometer navigation has not been demonstrated [12], and the time since the introduction of this technology does not yet allow for sufficient long-term follow-up, where the reduction in the number of outliers could show significant progress in terms of loosening. [PERSON] et al. have described the results of the main studies about accelerometers in a systematic review [12]. Five of nine studies found a better HKA restoration in accelerometer-assisted TKA [13,14,25,30,31], while the other four found no difference between the two procedures (conventional vs. accelerometer-assisted) [18,26,32,33]. More recently, [PERSON] et al., in a prospective study using 122 TKA, found a good accuracy of accelerometer navigation system for tibial cut, finding a better precision on TMA and HKA angles (89.2 \(\pm\) 1.7\({}^{\circ}\) and 179.2 \(\pm\) 1.8\({}^{\circ}\) in accelerometer-navigation group, and 87.4 \(\pm\) 1.5\({}^{\circ}\) and 177.3 \(\pm\) 2.8\({}^{\circ}\) in conventional technique group) [34]. Regarding femoral component coronal-axis alignment, seven of nine studies found a better precision with accelerometer-based navigation [13,14,18,25,30,31]. Nevertheless, there was no significant difference in sagittal alignment. However, [PERSON] et al. report better results in the short term (mean follow-up time 2.7 months) [35]. There are no specific complications or revisions due to the accelerometer system reported in the literature. Indeed, there are no bone trackers, irradiated exams, or other invasive steps with this kind of system. The accelerometer systems also present an interesting facet in complex cases. Indeed, this system can be helpful when the mechanical ancillary device fails, particularly in the case of extra-articular deformity [36; 37], intramedullary obstacle, or kinematic alignment [38]. This study had some limitations. First, only the tibial cut was assessed because the workflow of the conventional technique for the femur starts with the posterior cuts, which drives the distal cuts.