Risedronate preserves bone architecture in postmenopausal women with osteoporosis as measured by three-dimensional microcomputed tomography

The deterioration of trabecular microarchitecture induced by elevated bone turnover is increasingly recognized as a factor in the pathogenesis of osteoporotic fractures. We investigated the effect of the reduction of turnover with risedronate on trabecular architecture in postmenopausal women with osteoporosis. Iliac crest bone biopsy specimens taken before and after 3 years of treatment from patients receiving risedronate 5 mg daily (n = 21) or placebo (n = 17) were analyzed using 3-D microcomputed tomography. We found a significant correlation between baseline bone turnover and bone loss in the placebo group, providing evidence that higher turnover induced higher bone loss leading to a greater degree of architectural degradation. When patients were classified into two groups based on baseline bone turnover (MS/BS less than or greater than the median value for the entire cohort), significant decreases in trabecular bone volume (BV/TV, P = 0.009) and trabecular thickness (Tb.Th*, P = 0.008) and an increase in marrow star volume (Ma.St.V, P = 0.008), a measure of trabecular porosity, were observed in the higher turnover (MS/BS> median) placebo-treated patients. The trabecular structure shifted from plates to rods as shown by an increase in structure model index (SMI, P = 0.028) and bone surface to bone volume ratio (BS/BV, P = 0.006). The changes from baseline in the lower turnover (MS/BS