Associations between trabecular bone score and vertebral fractures in patients with axial spondyloarthritis

Objectives. To compare trabecular bone scores (TBS) between axial SpA (axSpA) patients with and without vertebral fractures and investigate associations between TBS and vertebral fractures. Methods. Two hundred and fifty-five patients fulfilling the imaging arm of the Assessment of SpondyloArthritis International Society axSpA criteria were enrolled. TBS and BMD were assessed using dual-energy X-ray absorptiometry. Vertebral fracture of the thoracic and lumbar spine was defined according to the Genant criteria. Osteoporosis risk factors, inflammatory markers, DAS and spinal structural damage were also assessed. Univariate logistic regression analysis was performed to identify factors associated with vertebral fractures. Results. There were 31 vertebral fractures in 28/255 axSpA patients (11%). The mean (S.D.) TBS was 1.39 (0.11) and 1.30 (0.13) in patients without and with vertebral fractures, respectively (P < 0.001). BMD in the femoral neck was lower in patients with vertebral fractures (P = 0.027), but BMDs in the lumbar spine and total hip were not. Univariate logistic regression analyses identified old age (≥50 years), TNF inhibitor treatment, the presence of syndesmophytes and a low TBS (<1.23) as associated with prevalent vertebral fractures [odds ratio (95% CI): 6.9 (2.0, 24.4), 2.4 (1.0, 5.5), 5.5 (2.2, 13.5) and 5.3 (2.0, 14.1), respectively]. TBS has a better discriminatory value than BMD at the total hip for prediction of vertebral fractures in axSpA patients (P = 0.034). Conclusion. Similar to individuals with primary osteoporosis, axSpA patients with vertebral fractures have a lower TBS. This suggests that TBS has the potential to predict future vertebral fractures in patients with axSpA.