Background Osteoporosis (OP) is now a well recognised feature of ankylosing spondylitis (AS). Dual energy x-ray absorptiometry, which is the most routinely used method to assess OP, fails to demonstrate spine OP in patients with late stage disease (syndesmophytes and facet joints ankylosis). Therefore, quantitative computed tomography (QCT) is the only method that can evaluate correctly the spinal OP in patients with advanced spinal changes.
Objectives To study OP prevalence in AS using QCT and relationship between OP and AS symptomatic and structural severity.
Methods 27 patients with AS were enrolled prospectively: 24 men (88.8%) and 3 women with mean age of 37.7 ± 9.2 years [17–66] and mean disease duration of 7.6 ± 4.7 years [0.4–19]. The patients were studied clinically, radiologically and by QCT.
Results OP at the lumbar spine as defined by Z score < -1 was observed in 11 patients (40.7%). Osteoporotic patients were older than normals (42.3 yrs (9.8) vs 34.6 (7.6); p = 0.03) and had more severe disease as showed the significant statistical differences in symptomatic and structural parameters (chest expansion, BASMI, BASRI, and syndesmophyte score). There was a negative significant statistical correlation between Z score and Schöber index, chest expansion, BASMI and radiological indexes (syndesmophytes score, BASRI).
OP is frequent in AS.
Patients with AS are more susceptible to develop OP when they have active and severe disease.
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