Introduction: Ageing bone marrow shifts to increase the activities of adipocytes and osteoclasts and decrease osteoblast function, resulting in osteoporosis.1 Using MRI, we investigated whether bone marrow obesity and ischemia were related to osteoporosis in older adults.
Materials & methods: We prospectively recruited 39 normal men (n=16) and postmenopausal women (n=23) aged at least 50 years for MRI and DXA. Participants were categorized as normal BMD, low bone mass (LBM), or osteoporotic, determined by T-score via DXA. Each participant underwent a 1.5-T MRI of the lumbar spinal region (centered at L1 and L2) using: (1) a STEAM 1H-MRS; (2) 6-point IDEAL reconstruction; and (3) an axial DCE-MRI. To perform pixel-by-pixel comparisons, imaging locations of the latter two were matched.
Results: Excellent linear correlation was found between 6-pt IDEAL and MRS (R2=0.758, P<0.001). In postmenopausal women, significant negative correlations were found between regional fat fraction and BMD (P=0.003; Table 1): fat fraction differed between normal BMD and LBM (P=0.003) and normal BMD and osteoporotic (P=0.01) groups. In contrast, significant positive correlations were found between regional bone marrow blood perfusion and BMD (P=0.02): perfusion differed between normal BMD and LBM (P=0.04) and normal BMD and osteoporotic (P=0.04) groups. In men, no significant correlations were found between regional fat fraction and BMD (P=0.42; Table 2): normal BMD vs. LBM groups yielded P>0.999, and normal BMD vs. osteoporotic groups yielded P>0.999. Correlations between regional bone marrow perfusion and BMD were also absent (P=0.30): BMD vs. LBM groups yielded P=0.04, and normal BMD vs. osteoporotic groups yielded P=0.50.
Discussions: Investigating regional characteristics and homogeneity of vertebral fat content and blood perfusion using advanced MRI techniques gave results that agree with previous studies showing a rapid decrease in lumbar BMD, increase in marrow fat content, and decrease in marrow blood perfusion after bilateral oophorectomy or menopause in women.2,3 This correlation was not observed in men. Endothelial dysfunction potentially causes impaired bone perfusion in osteoporosis.4
Conclusion: Bone marrow obesity and ischemia can indicate osteoporosis in postmenopausal women.
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