## 3 Results
### The Results of the Numerical Simulation of the Uniplane Opening Tibial Osteotomy  
The analysis of the results obtained from the numerical simulations relates to the maximal values and to the distribution of the von Mises stresses and of the main stresses obtained, with the purpose of evaluating the two studied parameters (the position of the cutting point and the correction angle) in order to optimally plan, from a geometrical and a dimensional point of view, the surgery. Figure 8a,b shows the distributions of the von Mises stresses in the CORA area, both on the inner and on the outer surface of the bone, for the scenario in which the cutting point was situated at a 30 mm distance to the tibial plateau, and there was a 14 degree correction angle. When observing the results of the analysis, one can notice a maximum equivalent stress on the outer wall of the tibia (Figure 8b) reaching 137.74 MPa, a reasonable value considering the large value of the correction angle (14 degrees). Regarding the state of the equivalent von Mises stresses inside the CORA hole (Figure 8a), high values of the stresses were observed, reaching a maximum of 196.7 MPa, values that could lead to the appearance of microcracks. The maximum principal stresses had higher values, with a maximum of 225.59 MPa achieved inside the CORA area. Figure 7: Experimental conduct of medial opening wedge HTO. The FEM analyses were performed similarly for the other previously indicated eight combinations of values, and the results are summarized in Table 2, where the maximum values are presented for both the equivalent von Mises stresses and for the maximum principal stresses. An increase in the values of these stresses could be noticed with the increase of the correction angle, a trend that is normal. Regarding the other variable, we noticed that the lowest values were recorded for the 40 mm value of the variable X1. An important conclusion is that positioning the cutting point at 40 mm from the intra-articular plane generated the lowest stresses in the CORA area. Figure 9a-d shows the distribution of the von Mises stresses in the CORA area, both on the inner and on the outer surface of the bone, for the other two scenarios regarding the position of the cutting point (40 mm, 50 mm distance to the tibial plateau) and for the same correction angle of 14 degrees. Figure 8: Equivalent von Mises stress in the CORA area—for X1 = 30 mm, X2 = 14 degrees, the inner surface (**a**) and the outer surface (**b**). Figure 9: Equivalent von Mises stress in the CORA area—for X1 = 40 mm, X2 = 14 degrees, the inner surface (**a**) and the outer surface (**b**) and for X1 = 50 mm, X2 = 14 degrees the inner surface (**c**) and the outer surface (**d**). Another important evaluation made was the comparative analysis of the von Mises stresses on the inner and the outer surfaces of the CORA area for all the three positions of the cutting point (30 mm, 40 mm, 50 mm) in the case of the highest correction angle, namely 14 degrees. As can be observed in Figure 9, the maximum value of the von Mises stress on the outer wall of the tibia is 127.52 Mpa for the value X\({}_{1}\) = 40 mm and 136.51 Mpa for the value X\({}_{1}\) = 50 mm. By determining what the difference was between the maximal values of the von Mises stresses inside the CORA area (Table 2) and the stresses from the outer wall of the tibia in the same area, we could also observe the manner in which the stresses propagated in the CORA area. In this sense, for the combination X\({}_{1}\) = 40 mm, X\({}_{2}\) = 14 degrees, we had the smallest value of the stress on the outer wall--127.52  Mpa--but also the biggest difference between the stresses on the inner and on the outter surfaces (64.13 MPA), from which resulted a smaller speed of propagation of the microfractures.