Experimental study on allogenic bone grafts.

The effects of various processing techniques on the biomechanical properties and the histological incorporation of bone grafts were investigated in a rat model over a 6 month period. The stiffness of bone increased after freezing to -80 degrees C and freeze-drying. Decalcified bone was very soft. Visco-elasticity was pronounced at 4 to 12 weeks and the stiffness of the graft increased at 16 weeks. This progressive rise in stiffness was in line with the progressive incorporation of the graft. The bone incorporation ratio is proposed as a histological indicator of osteo-inductive properties. It was found to be best in fresh autografts, followed by processed allografts (frozen, freeze-dried and decalcified) and fresh allografts. The values of these 3 groups showed a statistically significant difference.