Figure 4

Histomorphometric analysis of bone formation. For histomorphologic analysis of the mineralized area, Von Kossa stainings of samples of the left femur were performed. Histomorphometric analysis of the mineralized area was performed within a region of interest, defined as a trapezoid area with a length of 8,000 μm containing the defect in its center. The parallel sides of this trapezoid were perpendicular to the axis of the femur shaft and stretch between the cortical bone of the proximal and distal bone fragment. The defect area was marked manually and then compared to the total area of the region of interest ((A) 25×). Although nonunions were seen in the majority of animals, pronounced inter-individual differences within the groups were detected regarding bone formation. However, in one case (Ad.BMP-2 group), a complete union was achieved. A statistical comparison of the three groups showed little difference regarding the area of mineralized bone compared to the entire region of interest (B).