Erosive costovertebral joint arthritis as a novel feature of ankylosing spondylitis

Currently, sacroiliac joint (SIJ) arthritis is the sole imaging criterion for confirming a diagnosis of ankylosing spondylitis (AS). However, numerous studies have demonstrated that SIJ inflammation lacks specificity. Notably, some patients with non-radiographic axial spondyloarthritis (nr-axSpA) cannot be diagnosed with AS due to an absence of imaging changes indicative of SIJ arthritis, resulting in delayed diagnosis and treatment. The costovertebral joints (CVJs), similar to the SIJ, are synovial joints located adjacent to the vertebral column. The potential of the CVJ to serve as an indicator for the early diagnosis of AS warrants further investigation. This study utilized a retrospective research design to investigate the potential diagnostic value of CVJ arthritis in AS.

Patients diagnosed with nr-axSpA and AS at The Affiliated Hospital of Southwest Medical University between September 2018 and December 2023 were selected as the study cohort. Concurrently, healthy individuals undergoing routine medical examinations, matched for baseline characteristics, were recruited as the control group. The prevalence of CVJ arthritis among the different cohorts was assessed utilizing computed tomography (CT) and magnetic resonance imaging (MRI), with lesions being graded based on their severity. Furthermore, to the association between CVJ involvement and the formation of periosteal new bone (PNB) on the adjacent vertebral body's upper endplate was explored. Additionally, the link between CVJ arthritis and SIJ arthritis in the same patients was studied.

CVJ arthritis occurred in 29.2% of patients diagnosed with nr-axSpA, indicating a notably higher rate compared with the control group. CVJ arthritis occurred in 96.2% of patients with AS, which was significantly higher than that in the control group (7.2%, χ²=84.436, P<0.001). PNB was most likely to be distributed in the posterolateral part of the vertebral body adjacent to the CVJ. The severity of CVJ arthritis was positively associated with the incidence of PNB formation and moderately correlated with SIJ arthritis in the same patients.

CVJ arthritis was found in 29.2% of patients with nr-axSpA. Moreover, the severity of CVJ arthritis was positively associated with the incidence of PNB formation and moderately correlated with SIJ arthritis in the same patients. This finding suggests that CVJ arthritis could potentially serve as a novel biomarker for the diagnosis of AS.