Background/Purpose: Previous studies have shown that the risk of vertebral fractures is increased in patients with ankylosing spondylitis (AS). Prospective longitudinal data about radiographic vertebral fractures are scarce and little is known about the effect of tumor necrosis factor-alpha (TNF-α) blocking therapy on the development of vertebral fractures in AS.

Our objective was to determine the prevalence of radiographic vertebral fractures in patients with AS before start of TNF-α blocking therapy and to investigate the incidence of vertebral fractures after 4 years of follow-up.

Methods: Consecutive AS patients from the Groningen Leeuwarden AS (GLAS) cohort with available thoracic and lumbar radiographs at baseline and after 4 years of TNF-α blocking therapy were included. Patients fulfilled the modified New York criteria for AS and the ASAS criteria to start with TNF-α blocking therapy. Vertebral fractures were assessed by two independent readers using the Genant method and were defined as ≥20% reduction in vertebral height (grade 1 (mild), 20-25% reduction; grade 2 (moderate), 25-40% reduction; grade 3 (severe), >40% reduction). Bone mineral density (BMD) was measured with DXA and spinal radiographic damage with the modified Stoke AS Spine Score (mSASSS).

Results: 105 AS patients were included: 72% male, mean age 42±11 years, median symptom duration 16 years (range 1-47), and 83% HLA-B27 positive. In 27 (26%) of 105 patients, vertebral fractures were observed at baseline (average 1.7 fractures per patient). These patients were significantly older, had larger occiput-to-wall distance, and more spinal radiographic damage.

After 4 years of follow-up, 21 (20%) patients had new vertebral fractures. Most fractures were mild and occurred in the thoracic spine. Older age, higher BASFI, low lumbar spine BMD, use of anti-osteoporotic treatment, and presence of moderate vertebral fractures at baseline were significantly associated with the development of new fractures. Lumbar spine and hip BMD increased significantly during treatment. Patients with new vertebral fractures showed significantly less improvement in lumbar spine BMD than patients without new fractures (median change in Z-score 0.4 vs. 0.8).

Conclusion: The prevalence of radiographic vertebral fractures was 26% in AS patients with active disease before start of TNF-α blocking therapy. Although a significant increase in BMD was found, 20% of patients developed new vertebral fractures during 4 years of TNF-α blocking therapy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/development-of-new-radiographic-vertebral-fractures-in-patients-with-ankylosing-spondylitis-during-4-years-of-tnf-%ce%b1-blocking-therapy-results-from-the-glas-cohort/