Bone histomorphometry in renal osteodystrophy

On bone biopsies from patients with chronic kidney disease, measurements are made of the turnover, mineralization, and volume. Turnover depends on the bone formation rate and bone resorption rate; the former can be measured using tetracycline labelling. The osteoid width and bone apposition rate determine the mineralization rates. Bone volume includes both mineralized and unmineralized bone and is directly related to the porosity. Using these measurements, biopsies can be separated into the classic types of renal osteodystrophy: normal, adynamic, high-turnover, mixed, and osteomalacia. Fracture rates among these types are not consistent, but several studies have found high fracture rates with adynamic or osteomalacia. The bone density tests cannot distinguish between different types of bone histology.