Fine Structure of Remodeling Sites on Iliac Cancellous Bone in Senile Osteoporosis: A Study by Scanning Electron Microscopy Using an Improved Organic Specimen Preparation Method

We improved on the organic specimen preparation method in order to investigate the details of the functional state of bone in osteoporosis at high magnification level. The usefulness and possibilities of this method are discussed showing fine structural images of remodeling sites. Iliac bones of senile osteoporotic patients obtained by transilial biopsies were studied by scanning electron microscopy (SEM) using the improved preparation method. Excepting the region near the corticoendosteal surface, most of the iliac cancellous bone was composed of thin rod-shaped trabeculae. Remodeling sites on trabeculae appeared as concavities of various sizes and were easily distinguished from inert surfaces. The region near the cortico-endosteal surface showed a higher remodeling activity as compared with other regions. The morphological analysis of remodeling site by SEM made it possible to know its functional state. Five areas of different stages were distinguishable in remodeling sites, each corresponding to a different stage in the remodeling cycle: area in resorbing phase, in reversal phase, in early forming phase, in late forming phase, and in resting phase. The distribution patterns of the five areas in remodeling sites were investigated. More than half of the remodeling sites showed the heterogeneous composition: they were occupied by plural areas in different phases. Some remodeling sites were entirely occupied by a single area in reversal phase or in forming phase or resting phase. The remodeling site occupied by an area in resorbing phase alone was not found