## 4 Discussion  
The present study is an experimental animal study which evaluates whether the decellularized omentum could be used as an effective scaffold in critical bone defects. In the previous literature, it is well shown that decellularized scaffolds promote cellular adhesion and migration in addition to cell proliferation and differentiation [17]. We preferred omentum in our study because of its natural basis to increase the biocompatibility. In current literature, many studies show that omentum provides support and growth of \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & \multirow{2}{*}{**N**} & \multirow{2}{*}{**Quality of Union**} & \multicolumn{2}{c}{**Cortical**} & \multirow{2}{*}{**New Bone**} & \multirow{2}{*}{**Total Score**} & \multirow{2}{*}{**\(p\)**} \\  & & & **Development and** & & & **Formation** & \\ \hline \multirow{4}{*}{Control} & \multirow{2}{*}{12} & 2 & 0 & 1 & 3 & \\  & & (1–2) & (0–0) & (0–1) & (1–3) & \\  & & 3 & 3 & 3 & 9 & \\ \multirow{2}{*}{Omentum + Mesenchymal  stem cell} & \multirow{2}{*}{12} & (2–3) & (2–3) & (3–3) & (7–9) & \\  & & 1.5 & 0 & 1 & 2.5 & \\ \multirow{2}{*}{Omentum + PRP} & \multirow{2}{*}{12} & (1–2) & (0–1) & (1–2) & (2–5) & \\  & & 3 & 2.5 & 3.5 & 8.5 & \\ \multirow{2}{*}{Omentum + Mesenchymal  stem cell + PRP} & \multirow{2}{*}{12} & (2–3) & (2–3) & (2–4) & (6–10) & \\  & & 2 & 2 & 2 & 6.5 & \\ \multirow{2}{*}{\(\cdot\) Data are given according to median (minimum–maximum).} & \multirow{2}{*}{\(\cdot\)} & \multirow{2}{*}{\(\cdot\)} & \multirow{2}{*}{\(\cdot\)} & \multirow{2}{*}{\(\cdot\)} & \multirow{2}{*}{\(\cdot\)} \\  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Histopathological assessment scoring of groups according to [PERSON] et al. the cells as a bioreactor in soft tissues [18,19]. However, decellularized omentum has never been tried in orthopedic literature as a scaffold. Our study, for the first time, showed that decellularized omentum could be used as an efficient scaffold. We investigated momentum in animal models despite its human origin, but it should be kept in mind that the decellularization process enabled us to lose the antigenic activity of the omentum. Histologic data showed that ossification was seen, the defect shrank and resorption of the scaffold occurred. In addition, in groups in which the scaffold was used, it was seen that the decellularized omentum scaffold allowed cellular adhesion and proliferation and supported cellular vitality. These results make us think that the omentum is an inspiring scaffold that can be used in the treatment of critical bone defects. The other goal of the study was to find a way to increase bone healing in addition to a suitable scaffold. PRP was proven to increase bone healing in the literature previously [20]. In addition, we choose to use a previously described double-centrifugation method, as the literature supports that double centrifugation results in greater release of platelets and growth factors [21,22]. In our study, histologically, a PRP combination with omentum had higher organized ossification and bone mineralization than the omentum only group. In addition, the PRP + mesenchymal stem cell and omentum combination group had higher bone islands than the mesenchymal stem cell and omentum combination group. These results show that PRP increases bone union microscopically. For bone healing, the two methods, MSCs and PRP, were demonstrated to achieve improvement. Even though we prepared allogeneic PRP, we could not prepare allogeneic MSCs due to technical drawbacks. However, previous animal studies that used human-origin MSCs with or without a suitable scaffold illustrated no systemic or local rejection reactions, which encouraged us to design our study [23,24]. There are various studies regarding the effects of MSC usage in the healing of critical bone defects. In some studies, it was shown that MSC combinations increase osteoinduction and osteogenesis [25,26].