Severity of sacroiliitis and erythrocyte sedimentation rate are associated with a low trabecular bone score in young male patients with ankylosing spondylitis

Objective. To examine factors related to a low trabecular bone score (TBS) and the association between TBS and vertebral fractures in patients with ankylosing spondylitis (AS). Methods. One hundred patients (all male, aged < 50 yrs) 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. Clinical variables, inflammatory markers, and the presence of vertebral fractures were also assessed. Sacroiliitis grade and spinal structural damage were measured using the modified New York criteria and the Stoke Ankylosing Spondylitis Spine Score (SASSS). Results. The mean TBS was 1.38 ± 0.13. The TBS showed a positive correlation with BMD at the lumbar spine, femoral neck, and total hip. TBS negatively correlated with SASSS, whereas BMD at the lumbar spine showed a positive correlation. A significant decrease in TBS values was observed in patients with spinal structural damage (p = 0.001). Univariate analysis identified disease duration, erythrocyte sedimentation rate (ESR), sacroiliitis grade, and SASSS as being associated with TBS. Multivariate analysis identified ESR and sacroiliitis grade as being independently associated with TBS (p = 0.006 and p < 0.001, respectively). Ten patients had morphometric vertebral fractures. The mean TBS was lower in patients with vertebral fractures than in age-matched patients without fractures (p = 0.028). Lower TBS predicted vertebral fractures (area under curve = 0.733, cutoff = 1.311). Conclusion. 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.