Bone Abstracts

Background and objective: High-resolution magnetic resonance imaging (hrMRI) can assess trabecular bone microarchitecture but the number of image slices required for reliable assessment is unclear.

Methods: MRI was performed just below the growth plate of the proximal tibia from 20 healthy controls (all female; median age 21 years (range 18–35) and 10 cases (three mals: seven females; median age 19.5 years (range 16–48) with known bone abnormalities including osteogenesis imperfecta and other endocrinopathies using a 3T-MRI with a resolution of 0.3×0.3×0.3 mm. Images were analysed using Matlab to generate the trabecular bone microarchitecture parameters, including apparent trabecular volume to total volume (appBV/TV), trabecular thickness (appTbTh), trabecular number (appTbN) and trabecular separation (appTbSp). The mean values obtained from 20 of the most central images (20 images) were compared to that for ten images, five images and one image from the centre of the total image set using linear regression analysis. Co-efficient of variations (CV) within subject and between subjects were compared for the total and partial image set and significance level analysed with Levene’s test and Mann–Whitney U-test.

Results: The mean trabecular bone microarchitecture estimates from ten, five and one images were strongly and positively related to the estimates from 20 images for appBV/TV (r=1.00, r=0.99, r=0.97, all P<0.001), appTbTh (r=1.00, r=0.99, r=0.97, all P<0.001), appTbN (r=1.00, r=1.00, r=0.98, all P<0.001) and appTbSp (r=1.00, r=0.99, r=0.98, all P<0.001). The mean intra-subject CV (S.D.) for appBV/TV in healthy controls was 2.6% (1.1%) for 20 images, 3.0% (1.5%) for ten images and 3.1% (1.5%) for five images. Cases have higher mean appBV/TV CV (S.D.) at 3.7% (2.1%) for 20 images, 4.7% (3.0%) for ten images and 4.3% (3.1%) for five images; all P>0.05 when compared to that of controls. However, sub-analysis of the four cases with osteogenesis imperfecta, a more severe osteopathy, demonstrated even higher mean CV (S.D.) at 4.6% (2.7%) for 20 images, 7.1% (3.1%) for ten images and 5.9% (3.6%) for five images (P=0.183, P<0.005 and P=0.157 respectively).

Conclusions: These findings indicate that partial MRI sets can reliably represent a larger complete set of images when assessing trabecular bone microarchitecture parameters. However, in cases with severe abnormalities of bone health, a larger set of images may need to be analysed to improve precision.

Disclosure: The authors declared no competing interests.