A positive association was found between facet joint ankylosis (FJA) and syndesmophyte development, and between bridging syndesmophytes and FJA development in patients with radiographic axial spondyloarthritis (r-axSpA), according to results of a study published in Rheumatology (Oxford).

Spinal damage often presents as syndesmophytes and FJA among patients with r-axSpA.

Researchers sought to evaluate whether the presence of 1 lesion increased the risk for the other, using data from the Sensitive Imaging in Ankylosing Spondylitis (SIAS) cohort, which included patients with r-axSpA from Leiden, The Netherlands, and Herne, Germany.


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All participants met the modified New York (NY) criteria, had at least 1 inflammatory lesion on spinal magnetic resonance imaging (MRI), and had between 1 and 18 syndesmophytes on lateral cervical and lumbar conventional radiography.

Patients with r-axSpA underwent low-dose computed tomography (CT) and MRI of the whole spine at baseline and at 2 years. Vertebrae were scored for the presence and size of syndesmophytes and all facet joints were evaluated for ankylosis; MRIs were evaluated for inflammation.

Researchers explored 2 hypotheses: the association between the presence of FJA and new syndesmophytes on the same vertebral unit after 2 years, and the association between the presence of bridging syndesmophytes and the development of FJA on the same vertebral unit after 2 years.

The hypotheses were tested in 2 types of models: model A (the “change-score” model) examined the effect of the predictor at baseline on the increase in the number of lesions at follow-up. As an example, for hypothesis 1, model A evaluated the effect of the presence of FJA at baseline on the syndesmophyte change score (ie, ≥1 new syndesmophyte); and model B (the “autoaggressive” model) examined the effect of the predictor at baseline on the presence of a lesion in a vertebral unit at follow-up, which was adjusted for its presence at baseline (ie, the “autoregressor”). As an example, for hypothesis 2, model B evaluated the effect of a bridged syndesmophyte at baseline on the presence of at least 1 ankylosed facet joint in a vertebral unit at follow-up (status score), which was adjusted for the presence of at least 1 ankylosed facet joint in the vertebral unit at baseline.

All the models were adjusted for the presence of inflammation at baseline on the location of the outcome (ie, the presence of inflammation at baseline on the vertebral body for hypothesis 1 and the presence of inflammation in the posterior elements at baseline for hypothesis 2).

Researchers conducted additional analyses, using model A and model B, to evaluate the hypotheses on adjacent vertebral units and evaluate a dose-response effect between the bony lesions.

The low-dose CT scans at baseline and at 2 years, along with MRI scans at baseline, from a total of 51 patients were included in the analyses. The mean participant age was 49 years. Both FJA and bridging syndesmophytes were present at baseline in every vertebral unit in at least 1 patient. Both the lesions occurred more often in the thoracic spine.

Baseline bridging syndesmophytes occurred more often than FJA at all levels (range, 10%-60% vs 8%-36%, respectively). In the majority of participants, the number of vertebral units with bridging syndesmophytes exceeded the number of vertebral units with FJA.

Odds ratio (OR) for the association between FJA at baseline and syndesmophyte development at follow-up (hypothesis 1) was 1.87 (95% CI, 1.20-2.92) for increase in the number of syndesmophytes (model A) and 1.69 (95% CI, 0.88-3.22) for vertebral units with new syndesmophytes (model B). In both model A and model B, vertebral body inflammation at baseline was significantly associated with the outcome.

The ORs for the association between bridging syndesmophytes at baseline and FJA development at follow-up (hypothesis 2) were slightly higher and significant in both models (OR, 3.55; 95% CI, 2.03-6.21 for model A and OR, 3.30; 95% CI, 2.14-5.09 for model B).

The researchers concluded, “…FJA is connected to syndesmophyte development and should therefore also be considered and measured when studying structural damage in the spine.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Stal R, Sepriano A, van Gaalen FA, et al. Associations between syndesmophytes and facet joint ankyloses in radiographic axial spondlyoarthritis patients on low-dose CT over 2 years. Rheumatology (Oxford). Published online March 18, 2022. doi:10.1093/rheumatology/keac176