Study results published in the Journal of Bone Mineral Research found that although long-term treatment with tumor necrosis factor inhibitors (TNFi) improved bone mineral density (BMD) in patients with ankylosing spondylitis (AS), vertebral fractures and radiographic progression were still present over follow-up.

Patients with active AS were recruited from the Amsterdam Spondyloarthritis cohort and followed after TNFi treatment initiation for a mean duration of 4.5 years. Patients were selected for inclusion in the present analysis based on the availability of dual-energy x-ray absorptiometry scans and radiographs at baseline and at 4 years’ follow-up. BMD of hip and lumbar spine, incidence of vertebral fractures, and radiographic progression scores were assessed at baseline and at the 4-year follow-up. BMD as observed on dual-energy x-ray absorptiometry scans was categorized according to the World Health Organization osteoporosis criteria: normal BMD, osteopenia, and osteoporosis. Vertebral fractures were assessed on lateral radiographs of the thoracic and lumbar spine. Genant score >1 or vertebral height loss ≥20% qualified as a fracture. The modified Stoke Ankylosing Spondylitis Spinal Score (m-SASSS) was used to determine radiologic progression.

The final study cohort comprised 135 patients with AS, among whom 40.1% had low BMD of the hip and 40.2% had low BMD of the lumbar spine. Following 4 years of TNFi treatment, these rates declined to 38.1% (P =.03) for low hip BMD and 25.3% (P <.001) for low lumbar spine BMD. At baseline, vertebral fractures were present in 11.1% of 131 patients with available radiographs. This value increased to 19.6% after 4 years of follow-up. A Genant score ≥2 (a “moderate” fracture grade) was found in 21.4% of patients with fractures at baseline and in 25.9% of patients with fractures after 4 years. Mean radiographic progression increased significantly from a median mSASSS score of 4.0 at baseline to 6.5 at the final time point (P <.001). All other disease activity parameters — including the Ankylosing Spondylitis Disease Activity Scale, Bath Ankylosing Spondylitis Disease Activity Index, C-reactive protein, and erythrocyte sedimentation rate — decreased significantly during the study course (P <.001).

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These data indicate that although TNFi treatment improved the disease course of AS by some metrics, it did not inhibit radiographic progression or decrease the number of vertebral fractures. As such, investigators recommended thoracic spine radiographs during follow-up care of patients with AS to carefully monitor the development of any vertebral fractures, particularly during treatment with TNFi. Further research is necessary to elucidate the proper course of treatment for patients at particular risk for vertebral fractures.

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Reference

Beek KJ, Rusman T, van der Weijden M, et al. Long-term treatment with TNF-alpha inhibitors improves bone mineral density but not vertebral fracture progression in ankylosing spondylitis [published online January 28, 2019]. J Bone Miner Res. doi:10.1002/jbmr.3684