Age dependency of regional differences in BMD and TBS in human vertebrae

Introduction:

Bone mineral density (BMD) is being assessed in patients with dual-energy X-ray absorptiometry (DXA) to identify osteoporosis. Further information provides the trabecular bone score (TBS). Studies have shown regional variation in bone volume and density inside the vertebrae. As these differences are not considered in DXA evaluations, we examined subregional BMD and TBS in vertebral bodies and their age dependency.

Materials and methods:

Anterior-posterior and lateral DXA scans were performed ex vivo on 31 thoracic vertebrae (T12) from women. Three groups were compared: “young” (32 ± 6 years), “aged without osteophytes” (70 ± 7 years) and “aged with osteophytes” (72 ± 4 years). The projection of the vertebral body was divided into 9 different subregions (3 × 3). BMD and TBS were measured for each subregion.

Results:

Our results show a significantly higher overall BMD in the young group compared to aged (p ≤0.05). Both BMD and TBS were heterogeneously distributed inside the vertebral body. Subregional BMD appeared higher in vertebrae with osteophytes but was not significant. In aged individuals, subregional BMD was more homogeneous compared to young individuals. TBS showed no significant differences between age groups. The regional distribution of TBS was not influenced by the age of the specimen. Age-dependent differences were only measurable in lateral DXA not in anteriorposterior DXA.

Discussion:

The observed regional differences in BMD might relate to typical fracture types. Considering the inability of conventional DXA to detect regional differences in bone volume, a stronger focus on BMD analysis of subregions in DXA studies could enhance fracture risk determination.

Key words:

DXA, TBS, regional differences, bone mineral density