[Spongiosa structure and polyostotic heterogeneity in osteoporosis. Mechanism of bone transformation, morphology, clinical significance].

Osteoporosis is the most frequent generalized bone disease. The clinical expression of postmenopausal osteoporosis is characterized by spontaneous fractures of the vertebral bodies which affect mainly the trabecular bone structure. Thus the morphological bone transformation in osteoporosis is of clinical relevance. The object of this study was to analyze quantitatively and qualitatively the distribution of three-dimensional structure of cancellous bone in the human spine in osteoporosis. Therefore the complete anterior column of the spine and bone biopsies of the iliac crest of 11 autopsy cases with proven osteoporosis and 26 autopsy cases without primary or secondary bone disease were removed. A 1-mm-thick prepared sagittal section through the center of all vertebral bodies was embedded undecalcified in plastic and stained on the surface using a modification of the von Kossa method. This technique allowed combined two- and three-dimensional measurements simultaneously; these included evaluation of trabecular bone volume, trabecular interconnection, trabecular thickness, and trabecular number. The quantitative spine deformity index and qualitative analysis of the trabecular bone structure completed the investigation. The bone loss in osteoporosis is a loss of structure and the loss of whole trabeculae caused by perforations. The age-related decrease of trabecular bone mass is due to the transformation from plates to rods. Patient with osteoporosis show pathologically diminished trabecular bone volume and apparently reduced trabecular interconnection, while trabecular thickness and trabecular number show age-dependent change. The polyostotic heterogeneity in osteoporosis is immense. Neighboring vertebral bodies show differences of up to 100% in bone volume and bone structure. Due to this fact it is impossible to define a threshold for osteoporotic fractures. At the moment the transformation and loss of trabecular bone structure in osteoporosis is assumed to be irreversible; therefore, early prophylaxis is necessary to prevent clinical manifestations of these changes of bone.