Bone remodeling in predialysis chronic renal failure: how does the choice of index for mineralizing surface influence...

To study how calculating bone dynamics with different indices of mineralizing surface (MS) may influence the interpretation of bone remodeling in chronic renal failure (CRF) and to discuss which of three often used indices may be closest to the true MS, we compared bone histomorphometry in predialysis patients with moderate (se-creatinine less than 400 mumol/liter) and advanced CRF. All were double-labeled with tetracycline and had no stainable bone aluminum. Bone dynamics were calculated with MS = double-labeled (dLS) + single-labeled surface (sLS), MS = dLS + sLS/2, and MS = dLS. As sLS was twice that of dLS in both groups and the label interval was only 10 days, most single labels were probably double labels, but unseparable due to wide and unsharp labels resulting from high rather than low bone turnover. Bone volume was the same in both groups, while osteoid and resorption indices, sLS, and bone formation rate (with MS = dLS + sLS) were increased in advanced CRF. dLS + sLS is higher than the true MS, but more representative for MS than dLS + sLS/2, with the true value between these two indices. Bone resorption, osteoid formation, and mineralization remain in balance even in advanced CRF. Osteomalacia is hardly the consequence of CRF alone.