Flexural rigidity in partially demineralized diaphyseal bone grafts

Control of biomechanical properties of demineralized diaphyseal bone allografts is required for their clinical application. Therefore, the changes in flexural rigidity in human fibulae were investigated as a function of the demineralization depth using a nondestructive bending test. Starting at the facies medialis, the flexural rigidity was determined in 24 planes at 15 degrees sequential angular increments, which allowed data collection around the circumference of the bone. Test bones included 4 pairs of left and right human fibulae and 15 single fibulae. The elliptical distribution of the flexural rigidity of left and right fibulae and single fibulae before and after demineralization was compared. The stiffness index and the area ratio were defined as parameters to describe the mechanical status of the test bones. Results show that the rigidity of diaphyseal bones is strongly dependent on the reduction of their cortical thickness by demineralization. A mathematical model allowing prediction of the reduction of the rigidity of diaphyseal bone grafts as a function of the demineralization depth is presented.