CERVICAL ZYGAPOPHYSEAL JOINT INVOLVEMENT IS ASSOCIATED WITH RADIOGRAPHIC DAMAGE AND IMPAIRED SPINAL MOBILITY IN AXIAL SPONDYLOARTHRITIS

Aim:To evaluate the clinical, functional, and radiographic implications of cervical facet joint [zygapophyseal joint (ZJ)] involvement and ankylosis in patients with axial spondyloarthritis (axSpA). Material and Methods:This retrospective study included 132 patients diagnosed with axSpA. Cervical ZJ involvement and ankylosis were assessed using the De Vlam scoring method. Patients were stratified according to ZJ involvement (score ≥1) and complete ankylosis (score =3). Clinical, functional, and radiographic parameters were compared between groups. Multivariate linear regression was performed to identify independent associated factors, of impaired cervical mobility, as measured by cervical rotation. Results:ZJ involvement was observed in 24 patients (18.3%), and ankylosis was observed in 11 (8.4%). Patients with ZJ involvement had significantly higher Bath Ankylosing Spondylitis Metrology Index scores, reduced cervical rotation, greater tragus-to-wall distance, and elevated cervical and total modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). ZJ ankylosis was associated with male sex, hip involvement, cervical syndesmophytes, sacral enthesitis, and a higher prevalence of sacroiliac joint ankylosis. Notably, among patients with cervical ZJ involvement, 7/24 (29.2%; 5.3% of the overall cohort) had no anterior cervical damage (mSASSS=0). In multivariate analysis, both the De Vlam ZJ score (b=0.377, p<0.001) and cervical mSASSS (b=0.277, p=0.012) were independently associated with reduced cervical rotation. Conclusion:Cervical ZJ involvement and ankylosis are associated with greater structural damage and reduced spinal mobility in axSpA. A subset of patients with ZJ ankylosis had no anterior cervical damage, highlighting the added diagnostic value of posterior structural assessment. Including posterior spinal evaluation may enhance functional assessment and improve prognostic accuracy.