Inflammatory cytokines in horses with cervical articular process joint osteoarthritis on standing cone beam computed tomography.

BACKGROUND Standing cone beam computed tomography (CT) provides cross-sectional imaging of the caudal cervical articular process joints (CAPJs) in the sedated horse, though the clinical implications of osteoarthritis (OA) identified on CT in this location are unknown. Increases in concentrations of intra-synovial cytokines could lend support to the clinical significance of CAPJ OA identified on this imaging modality. OBJECTIVES Investigate the presence and concentration of intra-synovial inflammatory cytokines in CAPJs with and without standing cone beam CT evidence of OA using an equine specific multiplex assay. STUDY DESIGN Prospective clinical study. METHODS Standing cone beam CT of C5-6 and C6-7 was performed on horses with CAPJ OA and control horses. Synovial fluid samples of the CAPJs of C5-6 and C6-7 were obtained bilaterally using ultrasound guidance and analysed for concentrations of IFN-γ, IL-1β, IL-6, IL-10, IL-17 and TNFα with the Milliplex® multi-analyte profiling kit. CT Images were retrospectively graded using a novel grading scheme. Significant differences between concentrations of inflammatory cytokines between joints with different categories of osteoarthritis severity were explored using a Wilcoxon rank-sum test or Kruskal-Wallis test. RESULTS Concentrations of intra-synovial cytokines were higher in joints with moderate to severe OA when compared to joints with no or mild OA, with differences in concentrations of IL-17 reaching statistical significance (P = .007). MAIN LIMITATIONS Limitations include discrepancy in number, age, and breed between control and OA populations, use of a novel grading scheme, and lack of a histologic gold-standard to confirm the presence and severity of CAPJ OA. CONCLUSIONS Differences in inflammatory cytokines between caudal CAPJs with and without evidence of moderate to severe osteoarthritis on standing cone beam CT exist. This finding lends support to the clinical relevance of a diagnosis of moderate to severe CAPJ OA in the caudal cervical vertebral column as identified with this imaging modality.