# Geometrical Planning of the Medial Opening Wedge High Tibial Osteotomy--An Experimental Approach
## 3 Results  
_Experimental Results Regarding the Study of the Postoperative Behavior of the Tibia-Osteosynthesis Plaque Assembly after Performing an Opening Osteotomy_  
The variation of the force relative to the deformation for the experimental tests presented in the previous chapter is shown graphically in Figures 6 and 7. The first experiment was performed with an 8 mm shift of the roller from the plane of symmetry of the machine. This shift of the roller materializes the Fujisawa point, taking into account the dimensions of the tibia-specimen. Figure 5: Test specimens prepared for the determination of displacements and strains occurred during offset loading (Fujisawa point) (**a**) and medial loading (**b**). A smooth increase in the compression force, but a good stability of the system can be observed in Figure 6. An approximately linear variation of the displacement up to the value of 1 mm can be observed initially for small forces up to 100 N. The variation curve then follows a parabolic rate up to a maximum displacement of 2.6 mm. The maximum input load is of 1000 N. The graphical processing of the experimental data was performed using the Instron machine software. When the load is applied in the middle of the knee joint (Figure 7), the diagram in Figure 7 shows behavior similar to the previous linear variation for loads up to 100 N, also followed by a linear increase, but with a higher slope. The system is less stable than the first one, with maximum displacements of up to 3.4 mm. The strains and displacements were assessed by means of the Aramis optical strain measurement system, and Figures 8-10 show the major strain \(\varepsilon_{1}\), the minor strain \(\varepsilon_{2}\), and the total displacements for four loading stages, for both medial and radial loading. Figure 6: Variation of the force relative to the displacement—offset loading at the Fujisawa point. Figure 7: Variation of the force relative to the displacement—medial loading. Figure 8: Values of the major strain \(\epsilon_{1}\) during Fujisawa point loading (**a**) and medial loading (**b**). Figure 10: Values of the displacement in the \(Oy\) direction during Fujisawa point loading (**a**) and medial loading (**b**). Figure 9: Values of the minor strain \(\epsilon_{2}\) during Fujisawa point loading (**a**) and medial loading (**b**). The following can be observed after analyzing Figures 8-10:  
* The predominant strains are the compression strains (minor strain \(\varepsilon_{2}\), the maximum values being 20% for medial loading and 10.6% for offset loading). * The major strain \(\varepsilon_{1}\) has the maximum values of 7.21% in the case of medial loading and 3.96% in the case of offset loading. * From the point of view of the displacements that occur, it can be easily seen that the maximum values in the vertical direction (_Oy_) are reached during the medial loading \(-\)2.01 mm, while at offset loading (Fujisawa point) the maximum value of the displacements is 0.639 mm in the positive direction of the _Oy_ axis. This is due to the fact that the stress is applied to the left of the tibial plateau and the stressing force tends to twist the upper part of this plateau in the trigonometric direction. Figures 8-10 show the experimental results for the loading stage of 100%. In the experiment, successive evaluations of the strains for four loading stages--namely 25%, 50%, 75%, and 100% of the total loading stroke--were also performed. The results are shown in Table 1.  
Figures 11 and 12 show the variations of the major strain \(\varepsilon_{1}\) and minor strain \(\varepsilon_{2}\) during medial and offset loading (Fujisawa point) in the four loading stages. As shown in Figure 11, the values of the major strains for the stage of the stroke of 25%, 50%, and 75% are almost double in the case of medial loading. For the stroke of 100%, the values are closer together, but with a higher value for this loading.