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.