Facet joint disease in patients with axial spondyloarthritis: A retrospective computed tomography study.

Background: Facet joints' (FJ) ankylosis was reported in patients with radiographic axial spondyloarthritis (r-AxSpA). However, a detailed FJ evaluation over the whole spectrum of AxSpA was not performed. We aimed to analyze structural lesions in the FJ of patients with different forms of AxSpA, using computed tomography (CT).

Methods: CT studies of the cervical/thoracic/lumbar spine, or of the chest/abdomen of patients with r-AxSpA or non-radiographic AxSpA (nr-AxSpA) (age ≤ 50 years) were analyzed for the presence of erosions, ankylosis, joint-space narrowing, osteophytes, subchondral sclerosis, subchondral cysts and vacuum phenomenon. Age- and gender-matched subjects without known rheumatic disease who performed spinal CT, formed the control group. Findings were compared between groups, separately for each spinal segment. Further, FJ findings between three subgroups of the axSpA subjects, including r-AxSpA with or without syndesmophytes, and nr-AxSpA, were compared.

Results: 959/666 FJs (49/44 patients) were assessed in the AxSpA/control group patients, respectively. The study group consisted of 16 r-AxSpA patients with syndesmophytes and 22 r-AxSpA patients without syndesmophytes, and 11 nr-AxSpA patients. FJ ankylosis was significantly more prevalent in all spinal segments of the r-AxSpA patients with syndesmophytes. Erosions were seen almost exclusively in patients with r-AxSpA. Joint-space narrowing and osteophytes were noted in all segments and all subgroups of AxSpA patients, including those with nrAxSpA.

Conclusions: Disease-specific FJ changes present almost exclusively in patients with r-AxSpA, while degenerative FJ changes are prevalent in all spinal segments and all AxSpA subgroups, suggesting that FJs can be affected early in the disease course.