Purpose: In addition to bone mineral density (BMD), trabecular microstructure contributes to skeletal strength. Our goal was to examine changes in trabecular microstructure in women on therapy.
Materials and methods: We followed 10 postmenopausal women receiving a bisphosphonate, risedronate (35 mg once weekly), over 12 months and examined trabecular microarchitecture with high resolution wrist MR images (hr-MRI). MRI parameters included bone volume/total volume (BV/TV), surface density (representing plates), curve density (representing rods), surface-to-curve ratio and erosion index (depicting deterioration). We assessed BMD of the spine, hip and radius and markers of bone turnover.
Results: Women had been receiving bisphosphonate therapy for 43+/-9 months (mean+/-SD) prior to the first MRI. Indices of hr-MRI demonstrated improvement in surface-to-curve ratio (13.0%) and a decrease in erosion index (12.1%) consistent with less deterioration (both p<0.05). BMD of the spine, hip and radius and markers of bone turnover remained stable. Parameters of hr-MRI were associated with 1/3 distal radius BMD (correlation coefficient 0.71 to 0.86, p<0.05).
Discussion: We conclude that hr-MRI of the radius demonstrates improvements in trabecular microstructure not appreciated by conventional BMD and provides additional information on parameters that contribute to structural integrity in patients on antiresorptive therapy.
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