Comparison of membranous bone healing characteristics in fetal and postnatal periods: an experimental study

In this experimental study, the postnatal and fetal membranous bone healing were investigated radiologically, histologically and levels of growth factors. Sixteen sheep fetuses and 16 sheep were included in this study. In the fetal group, 5 mm diameter ostectomy, and a 10 mm osteotomy were created in 90th gestational day. In the postnatal group, similar ostectomy and osteotomies were created. In the early period, radiologically similar radiolucencies in the ostectomy areas were seen in both groups. Histologically, fetal bone healing was decreased in the early postoperative period. However, it was accelerated in further time points. Histomorphometric analyses revealed accelerated fetal bone healing. TGF-beta1 levels were higher and then lower in early and late postoperative periods respectively in the fetal group. In the postnatal group, the levels of TGF-beta1 were lower and the differences between two groups were statistically significant in all time points (p < 0.05). The FGF and PDGF levels in both areas were higher in early postoperative period whereas lower in the late period in both groups. However, the fetal FGF levels were higher compared to the postnatal group (p < 0.05). The fetal PDGF levels were lower compared to the postnatal ones (p < 0.05). In conclusion, the calvarial bone gap model at the end of the second trimester of gestation in the fetal sheep model proved useful in examining the membranous bone healing. Histologically, the process of fetal bone healing seems similar to that of postnatal healing, albeit at an accelerated rate. Histomorphometric evaluation is a valuable tool in the evaluation of bone formation and gives more objective information about the ratio of bone formation.