Subchondral bone microarchitecture analysis in the proximal tibia at 7-T MRI

Background: Bone remodels in response to mechanical loads and osteoporosis results from impaired ability of bone to remodel. Bone microarchitecture analysis provides information on bone quality beyond bone mineral density (BMD). Purpose: To compare subchondral bone microarchitecture parameters in the medial and lateral tibia plateau in individuals with and without fragility fractures. Material and Methods: Twelve female patients (mean age = 58 +/- 15 years; six with and six without previous fragility fractures) were examined with dual-energy X-ray absorptiometry (DXA) and 7-T magnetic resonance imaging (MRJ) of the proximal tibia. A transverse high-resolution three-dimensional fast low-angle shot sequence was acquired (0.234 x 0.234 x 1 mm) Digital topological analysis (DTA) was applied to the medial and lateral subchondral bone of the proximal tibia. The following DTA-based bone microarchitecture parameters were assessed: apparent bone volume; trabecular thickness; profile-edge-density (trabecular bone erosion parameter); profile-interior-density (intact trabecular rods parameter); plate-to-rod ratio; and erosion index. We compared femoral neck T-scores and bone microarchitecture parameters between patients with and without fragility fracture. Results: There was no statistical significant difference in femoral neck T-scores between individuals with and without fracture (-2.4 +/- 0.9 vs. - 1.8 +/- 0.7, P = 0.282). Apparent bone volume in the medial compartment was lower in patients with previous fragility fracture (0.295 +/- 0.022 vs. 0.317 +/- 0.009; P = 0.016). Profile-edge-density, a trabecular bone erosion parameter, was higher in patients with previous fragility fracture in the medial (0.008 +/- 0.003 vs. 0.005 +/- 0.001) and lateral compartment (0.008 +/- 0 002 vs. 0.005 +/- 0.001); both P= 0.025. Other DTA parameters did not differ between groups. Conclusion: 7-T MRI and DTA permit detection of subtle changes in subchondral bone quality when differences in BMD are not evident.