EXAMINATION OF COMPACT-BONE MICRODAMAGE USING BACKSCATTERED ELECTRON-MICROSCOPY

A new staining technique using heavy metals (lead-uranyl acetate) has been developed to allow visualization of bone microdamage using both l ight microscopy and scanning electron microscopy operated in its back- scattered mode (BSE). At the light microscopic level, the number of mi crocracks counted in sequential sections of human ribs is the same for both the traditional basic fuchsin method of differentially staining microcracks and the new lead-uranyl acetate procedure. With BSE study, however, the number of microcracks observed is significantly reduced in all samples, because of the reduction of projection effect error as sociated with surface based imaging techniques. Application of the lea d-uranyl acetate staining technique to ex vivo-loaded crack propagatio n specimens showed an extensive ultrastructurally disrupted region ass ociated with the crack path through bone, consistent with the damage p rocess zone around cracks in toughened composite materials.