Dynamic evaluation of an osteoporosis rabbit model induced by ovariectomy and glucocorticoid with MR spectroscopy and micro-CT

Abstract

Objective To dynamically assess the regular pattern of both bone quantity and bone quality by means of MR spectroscopey and Micro-CT scanning in an osteoporosis rabbit model induced by ovariectomy and glucocorticoid, so as to explore the advantage of combining MRS with Micro-CT. Methods Sixty 8-month-old,mature female New Zealand white rabbits were allocated into three groups. Group B ( n =20 ) underwent bilateral ovariectomy (OVX) and Group C (n =20 ) underwent OVX combining with daily i. m. injections of methylprednisolone sodium succinate (MPS). Group A ( n =20 ) were used as sham controls. Bone marrow fat fraction (FF) and bone microstructure parameters were detected by MR spectroscopy and Micro-CT scanning at 2,4,8, and 10 weeks ( 5 rabbits at each time point every group) after operation in three groups. Results Lumber spine bone marrow FF in Group C was significantly increased over the time course of osteoporosis development with significant difference between Group C and Group A at 4,8,and 10 weeks after operation( all P＜0. 01 ). Bone mineral density(BMD) in Group C at 8 and 10 weeks after OVX was significantly decreased compared with Group A ( P＜0. 0l ). A moderately significant negative correlation between marrow fat content and bone microstructure parameters such as BMD, bone volume fraction, trabecular thickness, connectivity density, and trabecular plate number was found, while FF was positively correlated with structure model index and trabecular spacing( all P＜0. 01 ). Conclusions MRS and MicroCT scanning noninvasively evaluate the bone marrow changes of osteoporosis in the field of pathophysiology and microstructure. Combination of both modalities seems to be valuable in the early, comprehensive assessment of bone quality and bone mass in osteoporosis. Key words: Osteoporosis; Model, rabbit; Magnetic resonance spectroscope ; Micro-CT