## 3 Results and Discussion Related to the Evaluations of the Osseeointegration Process
### Bone Progression in Lattice Structures  
First of all, the bone progression was examined as a function of the location of the implants in the sheep's body, i.e., the bone progression in the metatarsal bone was compared to that in the tibia (Figure 13). The percentages of bone (dark blue in Figure 13) and of osteoid tissue (light blue in Figure 13) within the lattice are, respectively, 20.5% and 8.8% for the metatarsal bone and 26.6% and 3.9% for the tibia for the same sheep. Therefore, it seems that the bone progression is more accentuated in the tibia than in the metatarsal bone. This result confirms that vascularization, one of the four processes that come into play in implant stabilization, is better in the tibia than in the metatarsal bone.  
Then, the bone progression was examined as a function of the type of designs of the implants (Figure 14), as a function of the depths in the implants (Figure 15), and as a function of the lattice cell sizes (Figure 16). At 5 mm depth, the bone formation is almost complete for  
Figure 13: Two-dimensional (2D) XCT images of implant horizontal (**top**) and sagittal (**bottom**) slices showing the proportion of bone (in dark blue) within the implant (in yellow) compared to other areas (osteoid tissue is in light blue and metallic grains are in green), in the metatarsal bone and tibia. The green or red line in the smaller images located on the right of the main images indicate where the slices were extracted.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Angular Position around the Cylinder** & \(\mathbf{0}^{\circ}\) & \(\mathbf{45}^{\circ}\) & \(\mathbf{90}^{\circ}\) & \(\mathbf{135}^{\circ}\) & **Total** \\ \hline Number of pixels in the selected image area & 38 & 300 & 254 & 61 & 653 \\ \hline Number of pixels for which bone and & & & & & \\ metal have no contact & & 0 & 47 & 0 & 47 \\ \hline \% of pixels free of bone or metal & 0 & 0 & 18.5 & 0 & 7.2 \\ \hline BIC (\%) & 100 & 100 & 81.5 & 100 & 92.8 \\ \hline \hline \end{tabular}
\end{table}
Table 3: BIC evaluations performed on an area located close to the internal border, in the lattice region of the side-closed implant open at its bottom, labeled 1386, for different angular positions at the cylinder periphery.  
the 1200 \(\upmu\)m lattice cell size, whatever the implant design (Figures 14b,c and 15a,b). At 8 mm, the bone creation is not complete when the cylinder is laterally closed at all its height for the 1200 \(\upmu\)m lattice cell size (compare Figure 15b with Figure 15c). For the 900 \(\upmu\)m lattice cell size, bone creation exists but seems incomplete (Figures 14c and 16). However, it is not possible to conclude from this study whether the size of the lattice cell or its location in the sheep's body is the cause of this incomplete ossification.  
Two different depths in the same implant (side-closed cylinder (1386) 1200 \(\upmu\)m in the tibia)  
Figure 14: Bone progression in the three types of designs of the implants: (**a**) Side-open cylinder (1384) 900 \(\upmu\)m in the tibia; (**b**) Half-side-closed cylinder (1385) 1200 \(\upmu\)m in the tibia; (**c**) Side-closed cylinder (1386) 1200 \(\upmu\)m in the tibia.  
Figure 15: Bone progression at two different depths in the same implant (Depth 1 = 5 mm and Depth 2 = 8 mm): (**a**) Depth 1 at the nodes of the lattice’s cells; (**b**) Depth 1 at the center of the lattice’s cells; (**c**) Depth 2.