DOES BONE MINERAL DENSITY CHANGE IN EARLY AXIAL SPONDYLOARTHRITIS?

The rate of osteoporosis (OP) and the mechanism of its development in patients with ankylosing spondylitis (AS) and other spondyloarthrititides (SpA) have not been sufficiently investigated. Steady-state inflammatory disease activity is anticipated to be the leading factor of OP in AS. Objective: to investigate lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) in patients with early axial SpA (axSpA) and to reveal its association with inflammatory disease activity. Subjects and methods. A total of 150 patients (59 men and 91 women) aged 18 to 45 years with inflammatory back pain for ≥3 months and ≤5 years were examined. The diagnosis of axSpA was established in accordance with the 2009 ASAS criteria. BASDAI and ASDAS-CRP were used to assess activity and functional status was evaluated with BASFI. The examination included determination of HLA-B27, X-ray of the pelvis and LS, magnetic resonance imaging (MRI) of the sacroiliac joints, LS, and hip joints (in the presence of clinical signs of their involvement), and densitometry of LS (LI–IV) and FN. By taking into account the patients’ young age, the Z score was used to estimate BMD. The Z-score -2 SD or lower in at the least one of the regions examined is considered to be diminished BMD. Results and discussion. The median Z-score was -0.7 [-1.3; -0.2] SD for FN and -0.9 [-1.6; -0.6] SD for LS. Reduced BMD in at the least one of the regions examined was diagnosed in 27 (18.0%) patients. There was lower BMD in LS in 21 (14.0%) patients and in FN in 8 (5.3%). Two (1.3%) patients were diagnosed as having osteopenia in the two examined regions. There was no association between diminished BMD and age, gender, disease activity assessed with BASDAI, ASDAS-СRP, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). An association was found between inflammatory LS changes, as evidenced by MRI (MRI spondylitis), and reduced BMD in at least one of the examined regions. MRI spondylitis was detected in 27 (18.0%) patients. Decreased BMD in any of the examined skeletal regions was seen in 9 (33.3%) of the 27 patients having MRI spondylitis; the remaining 18 (66.7%) patients had normal BMD values. In the absence of MRI spondylitis, osteopenia was identified in 18 (14.6%) patients; normal BMD values were noted in 105 (85.4%); p = 0.03). There was also a relationship between the presence of MRI spondylitis and diminished BMD in the same region. LS osteopenia was found in 7 (25.9%) patients with MRI spondylitis and LS BMD remained within the normal range in 20 (74.1%). In the absence of MRI spondylitis, LS osteopenia was observed in 14 (11.4%) patients and LS BMD was normal in 109 (88.6%) (p < 0.05). Conclusion. There was an association between inflammatory LS changes, as evidenced by MRI, and reduced BMD in the same region. Our findings confirm the hypothesis that bone mass loss in the vertebral bodies in early axSpA results from local inflammation.