Abstract
Purpose: Ankylosing spondylitis (AS) not only results in pathological ossification of the spine, but can also be associated with osteoporosis. Due to the presence of syndesmophytes and possible involvement of the hip joints, classical dual X-ray absorptiometry (DXA) is of limited use in patients with advanced stages of AS. Trabecular bone score (TBS) is a method complementary to DXA, providing additional information about bone microarchitecture. There is a growing body of evidence for the usefulness of TBS in AS patients. The aim of this study was to assess the clinical utility of TBS in patients with AS. Methods: Patients with AS underwent DXA with additional TBS assessment. A cross-sectional analysis of the frequency of osteoporosis and bone microarchitecture deterioration and their association with patients’ characteristics was done. Results: A total of 51 male patients, mean age 40.7 years, were enrolled. Osteoporosis was diagnosed in seven patients (13.7%). Lumbar bone mineral density (BMD) was higher (p < 0.001) than femoral BMD, indicating abnormal BMD readings in the spine caused by syndesmophytes. Patients with DXA-diagnosed osteoporosis had lower TBS (p = 0.03) and TBS T-score (p = 0.043) values compared to patients without osteoporosis. However, disturbed bone microarchitecture (TBS < 1.23) was present in only three patients (5.9%). None of the patients had a history of an osteoporotic fracture. A lower TBS T-score (p = 0.032) was demonstrated in patients with sacroiliitis grade 4 than in patients with sacroiliitis grade 2, with no significant differences in BMD and T-score values. Conclusion: Among patients with early AS, the clinical utility of TBS is limited—it does not add value to DXA.
Highlights
Ankylosing spondylitis (AS) is a chronic progressive autoinflammatory disease predominantly affecting the axial skeleton
The exclusion criteria were: age < 20 years, body mass index (BMI) < 17 kg/m2 or >37 kg/m2, patients with diabetes mellitus, primary hyperparathyroidism, chronic kidney disease, and patients with significant motor impairment preventing proper dual X-ray absorptiometry (DXA) examination
There was no correlation between results, regardless of the location used, patients with DXA-diagnosed osteoporosis had significantly lower Trabecular bone score (TBS) (p = 0.03 used, patients with DXA-diagnosed osteoporosis had significantly lower TBS (p = 0.03) and and TBS T-score (p = 0.043) values compared to patients without osteoporosis (Figure 2)
Summary
Ankylosing spondylitis (AS) is a chronic progressive autoinflammatory disease predominantly affecting the axial skeleton. The progressive ossification of the vertebral column resulting from chronic inflammation leads gradually to irreversible loss of spinal mobility. In the first phase of the disease, bone erosion dominates over pathological bone formation. Inflammatory processes observed in AS patients may lead to osteoporosis. The incidence of osteoporosis in AS according to literature is estimated to be about two times higher than in the general population [1]. In AS patients, it is proposed that screening of osteoporosis should be performed after 10 years of disease duration [2], but there is little evidence as to which diagnostic method should be used [3]
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