Background The trabecular bone score (TBS) is a novel method used to evaluate bone microarchitecture. To date, the risk factors associated with a low TBS in AS are unknown and no study has examined the association between TBS and vertebral fracture in ankylosing spondylitis (AS) patients.

Objectives To examine factors related to a low trabecular bone score (TBS) and the association between TBS and vertebral fracture in patients with (AS).

Methods One hundred patients (all male, aged <50 years) who fulfilled the modified New York criteria for the classification of AS were enrolled. The TBS and bone mineral density (BMD) were assessed using dual-energy X-ray absorptiometry (DXA). Clinical variables, inflammatory markers, and the presence of vertebral fracture were also assessed. Spinal radiographic progression was measured using the Stokes AS spine score (SASSS). Multivariate linear regression analysis was performed to identify factors associated with TBS.

Results The mean TBS at the lumbar spine was 1.38±0.13. The TBS showed a negative correlation with disease duration and inflammatory markers, and a positive correlation with BMD at the lumbar spine, femoral neck, and total hip. It also showed a negative correlation with sacroiliitis grade. BMD at the lumbar spine positively correlated with SASSS, whereas TBS showed a negative correlation. A significant decrease in TBS values was observed in patients with spinal radiographic progression (p=0.001). Multivariate analysis showed that ESR and sacroiliitis were independently associated with TBS (p=0.006 and <0.001, respectively). Ten patients had morphometric vertebral fractures. The mean TBS was lower in patients with vertebral fracture than in age-matched patients without fracture (p=0.028).

Conclusions The TBS in young male patients with AS is associated with the ESR and severity of sacroiliitis. The TBS may be useful as a tool for assessing osteoporosis in AS.

Disclosure of Interest None declared