Long-term corticosteroid therapy induces mild changes in trabecular bone texture

The relative roles of bone mineral density (BMD) decrease and of microarchi tectural changes in corticosteroid-induced osteoporosis (CIOP) are debated. Our objective has been to evaluate both bone microarchitecture (by a fract al analysis of texture on radiographs) and BMD in corticosteroid (CS)-treat ed patients. In this study, 60 patients from a rheumatology unit with a mea n age of 60.6 +/- 14.8 years taking CS therapy for more than 6 months and a cumulative dose of prednisone over 1 g and 57 controls among age-matched p atients and hospital staff were recruited. Bone diseases and bone-modifying drugs (except calcium, vitamin D, and hormonal replacement therapy [HRT]) were considered as exclusion criteria. A fractal analysis of trabecular bon e texture was performed on calcaneus radiographs after an oriented analysis in 18 directions. The fractal analysis was based on the fractional Brownia n motion model. Results were expressed by H parameter (H = 2 - fractal dime nsion) in each direction, H-mean, being the average of 18 directions, H-min i the minimum, and H-maxi the maximum. BMD was measured by double-energy X- ray absorptiometry (DEXA) at the femoral neck (FN) and lumbar spine CLS). T he odds ratios (OR) were calculated for a variation of 1 SD. The mean durat ion and dose of CS therapy was 5.6 +/- 6.6 years and 16.9 =/- 19.7 g. CS th erapy was significantly correlated to a decrease in FN or LSBMD: OR = 1.95, 95% confidence interval (CI, 1.29-2.97) and OR = 3.19 (CI, 1.80-5.66), res pectively. The H-mean and H-maxi were significantly lower in the cases than in the controls: P = 0.03 and P = 0.02; OR = 1.67 (CI, 1.10-2.54) and OR = 1.75 (CI, 1.05-2.37). A similar trend was observed with H-mini but the dif ference did not reach the level of statistical significance: P = 0.06, OR = 1.57 (CI, 1.05-2.37). This study was repeated among cases and controls who had never taken HRT (respectively, n = 40 and n = 39). The results were si milar. Among patients taking CS therapy, the presence of nontraumatic fract ures was inversely related to BMD values but not to texture parameters. The se data have shown that long-term CS therapy induces both BMD decrease and trabecular bone texture changes. The effect of CS therapy was much stronger on BMD than on the fractal H parameter. These results are in accordance wi th previous studies showing a lower effect of CS therapy on bone microarchi tecture than on bone mass. These results can be contrasted with those obser ved in women with postmenopausal osteoporosis and vertebral crush fractures in which the variations in the fractal parameters are more significant tha n the BMD variations.