Background/Purpose: In ankylosing spondylitis (AS), syndesmophyte formation and ankylosis of the vertebral bodies are characteristic radiographic changes that are evaluated during follow-up. However, the facet joints are also involved in the disease process. Our aim was to investigate the prevalence and incidence of radiographic facet joint involvement in comparison to damage of vertebral bodies in the cervical spine of AS patients treated with TNF-α inhibitors. Second, to explore the association of facet joint involvement with patient characteristics and clinical outcome.

Methods: Consecutive patients from the Groningen Leeuwarden AS (GLAS) cohort who started treatment with TNF-α inhibitors because of active disease were included. Available lateral radiographs of the cervical spine at baseline and after 4 years of follow-up were scored by two trained and independent readers blinded to patient characteristics and time sequence. Facet joints of C2-C3 up to C6-C7 were scored according to the method of de Vlam et al. (0: normal, 1: joint space narrowing or erosion, 2: partial blurring or ankylosis, 3: complete blurring or ankylosis). Definite damage and progression of facet joints was defined as the presence and development of partial/complete blurring or ankylosis (score ≥2) in ≥1 facet joint, respectively. The modified Stoke AS Spine Score (mSASSS) was used to assess radiographic damage of the vertebral bodies. Definite damage and progression was defined as the presence and development of ≥1 (bridging) syndesmophyte, respectively.

Results: Of 108 included patients, 76% were male, mean age was 43±11 years, median symptom duration 17 years (range 1-50), 84% were HLA-B27 positive, mean BASDAI was 5.9±1.7, and mean ASDAS 3.8±0.8.

At baseline, 28 (26%) patients had definite damage of facet joints with on average 3 facet joints involved. Fifty-nine (55%) patients had definite damage of vertebral bodies. Damage of facet joints exclusively occurred in 5 (5%) patients. Patients with damage of facet joints were more frequently male, older, had longer symptom duration, more frequently a history of psoriasis, larger occiput-to-wall distance, and higher mSASSS of the cervical spine (all p<0.05).

After 4 years of follow-up, 13 (12%) patients showed definite progression of facet joints and 28 (26%) showed definite progression of vertebral bodies. Progression of facet joints without progression of vertebral bodies was seen in 8 (7%) patients.

Conclusion: In this observational cohort of AS patients with active disease, 26% had radiographic damage of facet joints whereas 55% had damage of vertebral bodies. Damage of facet joints was associated with male gender and more advanced disease. During 4 years of TNF-α blocking therapy, 12% showed definite progression of facet joints. More than half of these patients did not show progression of vertebral bodies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/radiographic-damage-of-facet-joints-and-vertebral-bodies-in-the-cervical-spine-in-patients-with-ankylosing-spondylitis-treated-with-tnf-inhibitors/