Cortical bone analysis in a predialysis population: a comparison with a dialysis population

This study was designed to characterize cortical bone by histomorphometry in a predialysis population, to correlate turnover, mineralization, and volume between cortical and trabecular bone, and to compare the findings with those in patients treated with maintenance dialysis. We evaluated cortical bone by histomorphometry in 16 patients with stage 3 or stage 4 chronic kidney disease and in 16 dialysis patients. Dual-energy X-ray absorptiometry (DXA) of the distal end of the forearm was performed in seven predialysis patients, and the findings correlated with histologic parameters. Predialysis patients compared with dialysis patients showed increased cortical bone thickness (p = 0.027) and decreased osteonal bone formation rate (p = 0.020) and adjusted apposition rate (p = 0.018), mainly for external cortical bone. In this predialysis population, trabecular bone volume positively correlated with external cortical porosity (r = 0.723, p = 0.003), external cortical thickness (r = 0.569, p = 0.034), and external osteonal accumulation (osteonal osteoid thickness, r = 0.530, p = 0.05; osteonal osteoid volume to bone volume ratio, r = 0.921, p < 0.001; and osteonal osteoid surface to bone surface ratio, r = 0.631, p = 0.016). These correlations were not observed in the internal cortical bone. Cortical osteonal mineralization surface negatively correlated with DXA Z and T scores and bone mineral density for the distal end of the forearm. The osteonal bone formation rate of both internal cortical bone and external cortical bone correlated with Z score (r = -0.975, p = 0.005 and r = -0.880, p = 0.021 respectively). We found no significant correlations between cortical thickness or porosity and DXA parameters for either external cortical bone or internal cortical bone. Our results suggest that a greater degree of kidney disease is associated with thinner cortices, eventually contributing to the higher fracture rate observed in the chronic kidney disease population. In predialysis patients, parathyroid hormone seems to have a modulating effect on both trabecular bone and cortical bone, particularly in external cortical bone.