Pathologic assessment of bone

Bone biopsy is an established diagnostic and investigative procedure that allows direct visualization of bone cells and structure and provides an indirect measure of bone turnover. It is widely used in management of metabolic bone disease and to explain any unclear biochemical abnormality affecting bone metabolism; it should become more widely used as its availability increases. Bone biopsy defines a variety of mineralization defects caused by fluoride, diphosphonates, and aluminum, and it provides unique insight into bone loss with age and with osteoporosis. It is necessary for evaluating rapidly progressive osteoporosis and it can be particularly useful for differentiating osteoporosis from osteomalacia. Although osteomalacia is often the result of decreased dietary vitamin D, there are recognized risk factors, such as previous gastric surgery or chronic renal disease. Nonetheless, clinical findings in osteomalacia are often rather subtle, and there may be few biochemical findings. Hence, if the patient is an elderly woman, and therefore also at risk for osteoporosis, the distinction can be difficult. Imaging studies are not likely to be helpful, since both disorders lead to decreased bone mass, usually at the same sites. The diagnostic criteria for osteomalacia are increased extent of osteoid surfaces, increased osteoid thickness, and thickened osteoid seams, in conjunction with a decreased calcification rate (as calculated by tetracycline labeling) and decreased calcification fronts. Osteoid volume alone is not an adequate diagnostic criterion, because it may also be increased in Paget's disease and hyperparathyroidism. Finally, biopsy is a valuable means to assess the effect of potential therapeutic agents on bone and bone cells.(ABSTRACT TRUNCATED AT 250 WORDS)