# Bone Substitutes Scaffold in Human Bone: Comparative Evaluation by 3D Micro-CT Technique
## 3 Results  
Acquired 2D images slices of each biomaterial sample and all the extracted specimens of the implants, including the ones of the preliminary clinical study [31; 33], were elaborated in order to perform the morphological analysis and to define the 3D reconstructed models. The morphometric parameters acquired, represent the percentage volume-bone volume fraction (BV/TV) in %; the specific surface examined-specific bone surface (BS/BV) in mm\({}^{-1}\); the percentage of empty spaces with respect to the total volume-porosity in %; the thickness of the trabecular bones-trabecular thickness (Tb.Th) in \(\upmu\)m and the distance between the trabeculae-trabecular separation (Tb.Sp) in mm\({}^{-1}\). The main morphological results for the selected biomaterials, and for the ICB, investigated in the preclinical phase before the implantation, are indicated in Table 2.  
Figure 1: Flow chart of the clinical study. Among the synthetic derivatives (Table 1), the biomaterial that resulted in being most similar to human bone, in particular in reference to the ICB values of porosity and BV/TV, turned out to be the ceramic hydroxyapatite (2b, Table 2). Nevertheless, variations are relevant for the BS/BV and the Tb.Th, which is noticeably different, 0.16 \(\upmu\)m with respect to the ICB value of 0.31 \(\upmu\)m.  
At the end of the in-vitro microtomographic experimentation, 3D images of selected parts of the specimens were defined in order to better display the interconnectivity of the structures observed, Figure 2. The negative coloring used allowed underling the connectivity density, i.e., the presence of communication spaces and connections among the porosities. The three products (1a, 1b and ICB), showed a higher interconnection among the internal empty spaces (Figure 2A-C) compared to the other materials (2b, 3a and 4a). Furthermore, 3D full models were reconstructed as shown in Figure 3. The models, regarding Part 1 and here analyzed again, were reported to allow the comparison among all the samples. The reconstruction of the complete samples let a faster qualitative visualization of the selected biomaterials structural differences. For the clinical phase, the micro-CT analysis was performed again on the extracted implants. The main morphological results for the selected biomaterials and in reference to the test and control site are indicated in Table 3, including the data previously reported in [33]--specimens 1a and 2b. The percentage variation--the relative difference between the values of each test and control specimen--of the results obtained for the specific parameters (Table 3), e \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Group** & **Label** & \begin{tabular}{c} **BV/TV** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} **BS/BV** \\ **(mm\({}^{-1}\))** \\ \end{tabular} & **Porosity (\%)** & \
\begin{tabular}{c} **Tb.Th** \\ **(\(\upmu\)m)** \\ \end{tabular} &
\begin{tabular}{c} **Tb.Sp** \\ **(mm\({}^{-1}\))** \\ \end{tabular} \\ \hline
1-Bio-bone & 1a & 28.73 & 18.30 & 71.27 & 0.22 & 0.51 \\
1b & 26.59 & 14.05 & 73.41 & 0.27 & 0.68 \\
2-HA & 2b & 31.69 & 23.88 & 68.31 & 0.16 & 0.47 \\
3-TCP & 3a & 24.13 & 11.09 & 75.87 & 0.28 & 0.52 \\
4-polymer & 4a & 91.77 & 2.66 & 8.22 & 0.49 & 0.22 \\ Iliac crest &
\begin{tabular}{c} ICB \\ bone \\ \end{tabular} & 39.43 & 11.69 & 60.57 & 0.31 & 0.61 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Morphological parameters of the biomaterials selected before the implantation. Figure 2: 3D images of selected parts of the samples, each image shows the positive (upper part) and negative (lower part): (**A**) BioOSS®, 1a; (**B**) Biogen®, 1b; (**C**) ICB; (**D**) ENGIpor®, 2b; (**E**) Bioset, 3a and (**F**) SINTbone, 4a. porosity, variation from about 8.7% for the specimen 2a test to about 67% for 3a test and lower BV/TV, from about \(-\)68.5% for 3a test to \(-\)8% for 2a test. The maximum values of porosity were obtained for the 1b test and for the 3a test.