Uses and limitations of bone biopsy in management of metabolic bone disease.

Bone biopsy is now an established diagnostic and investigative procedure which is widely used in the management of metabolic bone diseases. Its unique feature is that it facilitates direct visualization of bone cells and bone structure and, through double tetracycline labelling, allows the indirect measurement of bone turnover. Its main diagnostic contribution has been in unravelling the complexities of renal osteodystrophy, which consequently is now much better understood. However, it has also uncovered a variety of mineralization defects caused by agents such as fluoride, diphosphonates and aluminum that might otherwise have bone unsuspected clinically. Its main investigative roles have been to provide unique insight into the mechanisms of bone loss with age and in osteoporosis, and to assess the effects on bone and bone cells of potential therapeutic agents in established osteoporosis. This has been possible through the use of histomorphometry, which is used to quantify changes in bone volume and turnover as well as alterations in the microanatomical structure of bone that can reduce bone strength and increase the risk of fracture. Although most biopsies will continue to be taken for histomorphometry, recent studies have shown that specimens may be used to provide additional information such as quantitation and localization of elements within bone, and to provide bone cells for in vitro culture. It is likely that, in future, specimens will be taken from patients with various disorders so that the techniques of cell and molecular biology can be applied to harvested bone cells and thus provide a new dimension to our understanding of metabolic bone disease.