[Osteoporosis and metabolic bone diseases; clinical relationship]

Metabolic bone diseases with disturbed bone remodeling lead to loss of biomechanical quality and atraumatic fractures. Differential diagnosis, prevention and adequate treatment should already start early in the course of these disorders to prevent fractures. Thus, clinical osteology is more than the simplified connection "low bone mineral density--fractures--osteoporosis". This review summarizes physiological relations between bone tissue and calcium homoeostasis as well as the relation between structure and function. In addition, the main metabolic osteopathies "osteoporosis, primary hyperparathyroidism and osteomalacia" are presented from a clinical point of view. The importance and the diagnostic values of biochemical parameters and of the transiliacal biopsy are discussed. In this respect the quantitative measurement of the mineralization density (bone mineral density distribution = BMDD) seems to be of high value and extends the well established bone histomorphometry. This recently introduced method has the power to distinguish between small differences in the degree of mineralization of the matrix with high precision and reproducibility. The results of quantitative backscattered electron imaging in the scanning electron microscope improve the differential diagnosis of bone diseases with alterations in mineralization density, helps to detect mixed etiology (e.g. osteoporosis plus osteomalacia) and facilitate decision making for treatments. The value of biochemical, radiological, osteodensitometric and histopathological tests for diagnosis and treatment depends on the knowledge of the clinical relations and the complex interactions between calcium-, phosphate- and bone metabolism.