Background/Purpose: Ankylosing spondylitis (AS) is a chronic inflammatory rheumatological disease of unknown origin that primarily affects the axial skeleton, including the sacroiliac joints and spine, but also the peripheral joints and entheses.

This study aimed to evaluate the relationship between physical function, disease activity, spinal mobility and bone parameters in ankylosing spondylitis (AS)

Methods: ). Fifty patients were examined: 27 men and 23 women. None of the patients exhibited evidence of a fracture in any of the visualized vertebrae. The clinical assessment included Bath AS Disease Activity Index (BASDAI), AS Disease Activity Score (ASDAS-CRP), Bath AS Functional Index (BASFI), Bath AS Metrology Index (BASMI). Lumbar spine and femoral neck bone mineral density (BMD), spinal trabecular bone score (TBS) and the TBS T-score were calculated by dual-energy X-ray absorptiometry (DXA). 

Results: Using the WHO categorization scheme, 50% of the patients were deemed to have normal lumbar BMD, 36% were osteopaenic, and 14% were osteoporotic. This compares with normal TBS in 50% of the patients, with partially-degraded and fully-degraded micro-architecture seen in 34% and 16%, respectively. We found moderately strong inverse correlations between TBS and BASMI (r=-0.34; p=0.02), between the TBS T-score and BASMI (r=-0.35; p=0.01) and between femoral BMD and BASMI (r= -0.395; p=0.004). The correlation coefficient for the relationship between the TBS T-score and age was -0.29 (p=0.045), suggesting a weak inverse association, while TBS only exhibited a borderline inverse correlation with age (r=-0.27; p=0.06). Femoral BMD was moderately inversely correlated with age (r=-0.44; p=0.001). In addition, the lumbar spine TBS and TBS T-score were moderately to strongly correlated with BMI (both r=-0.65; p<0.001). No significant correlations were observed between bone parameters and other markers of disease activity, physical function, or applied therapy administered for AS. Subject`s age was independently associated with a femoral neck BMD < -1.00 (OR = 1.08, 95% CI 1.01 to 1.15, p=0.03). 

Conclusion:

In summary, spine BMD can be erroneously influenced by osteoproliferation, unlike the TBS and TBS T-score. The limitations in spinal mobility predicted abnormal results for these two TBS parameters. The TBS may be a better indicator of bone health than BMD in AS.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-between-bone-and-clinical-parameters-in-ankylosing-spondylitis/