Porosity-geometry interaction in the conservation of bone strength

Automated image analysis of a small sample of femoral cross-section radiographs has revealed a consistent difference in bone porosity relative to geometry. Two sub-periosteal fields were assessed microscopically, with field location determined with reference to the principal moment axes (Imax, Imin). The data indicate that: (1) porosity is greatest in the direction of maximum geometric resistance to bending, along the Imin axis; and (2) porosity differences between the Imax and Imin fields decrease as the bone becomes more circular in cross-sectional shape.