Comparison of osteogenic activity from different parts of induced membrane in the Masquelet technique

Background: The Masquelet technique is widely used to treat long-bone segmental defects because of its high success rate and low surgical difficulty. However, the cause of the uneven growth of bone grafts following this procedure remains unclear.Methods: Rats were randomly divided into four groups for analysis 2-, 4-, 6- and 8-weeks postoperatively and underwent a uniform surgical procedure to construct a 10 mm bone defect in the right posterior branch of the femur. Induced membrane specimens were harvested at the appropriate time points and divided into segments according to their location. Bone growth activity was assessed by immunohistochemistry, western blotting, and quantitative real-time polymerase chain reaction.Results: Mature blood vessels were more densely distributed at the proximal end of the bone defect than at other locations at all time points. The number of blood vessels on the same side of the longitudinal axis of the femur also varied depending on location. The difference between the proximal-anterior and distal-anterior regions within the induced membranes was most pronounced at 6 weeks postoperatively and decreased by 8 weeks postoperatively. The differences between the proximal-posterior and distal-posterior regions within the induced membranes were more pronounced. The expression of the growth factors bone morphogenetic protein-2 (BMP2), vascular endothelial growth factor A(VEGFA), and transforming growth factor-81(TGF-81) in the proximalposterior regions of the bone defect was almost always higher than that in other regions at the same time point. The expression of BMP-2 in the posterior regions of the bone defect was always higher than that in the anterior regions at the same end of the femoral longitudinal axis.Conclusion: The number and maturation of vessels in the proximal region of the induced membrane at the bone defect site were higher than those in the distal region, and the expression of growth factors was higher, with the highest induced membrane activity in the proximal-posterior regions of the bone defect. Therefore, there was inhomogeneity in induced membrane activity.