Purpose: Limited data are available on the relationship between treatment agents and sagittal balance in ankylosing spondylitis (AS). We investigated radiological features related to treatment agents and compared sagittal balance between patients treated with anti-tumor necrosis factor-α (anti-TNF-α) and those treated with nonsteroidal anti-inflammatory drugs (NSAIDs) and sulfasalazine (SSZ).
Methods: We prospectively enrolled 133 consecutive AS patients. Patients were eligible for the trial if they were under medical treatment with the same treatment agents for at least 1 year. All patients were treated initially with NSAIDs and SSZ. Sixty-nine patients achieved an excellent pain control outcome with these agents (group A). Sixty-four patients who reported of intractable low back pain were switched to anti-TNF-α treatment (group B). Twelve radiographic parameters were measured. Clinical outcome was assessed with the Bath AS Disease Activity Index (BASDAI), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). All parameters were measured at enrolment, upon changing treatment agents, and every 6 months during follow-up.
Results: The mean ESR, CRP, BASDAI, and thoracic kyphosis at baseline were significantly higher in group B. After treatment, group B had significantly higher lumbar lordosis (LL) and significantly better clinical outcomes. Correlation analysis revealed significant relationships between radiologic parameters and BASDAI. On multiple regression analysis, LL was a significant predictor of BASDAI.
Conclusions: This study demonstrated a clear association between treatment agents and radiologic parameters in AS. Anti-TNF-α treatment improved LL with improvement in clinical outcomes. Lumbar lordosis was a significant predictor of clinical outcome in AS patients treated with anti-TNF-α. These slides can be retrieved under Electronic Supplementary Material.
Keywords: Ankylosing spondylitis; Anti-TNF-α; Lumbar lordosis; Radiologic parameters; Sagittal balance.