34th Annual Scientific Meeting proceedings

Objectives:

Arthroscopic and histologic evaluation are good indicators of synovitis. Unlike for inflammatory synovitis, the involvement of cytokines in septic synovitis has not been well documented. The aims are to provide broader identification of inflammatory factors involved in septic versus non-septic synovitis and better describe the correlation between synovitis, arthroscopic and histopathologic evaluations of the synovial membrane.

Methods:

Three populations were defined: horses undergoing therapeutic arthroscopy (group1), horses with confirmed septic synovitis that underwent arthroscopic lavage (group 2), and horses presenting with periarticular injuries without synovial involvement (group 3). Synoviocentesis was performed and samples were processed for cytokine quantification using the MILLIPLEX® Panel. Groups 1 and 2 underwent synovial biopsy at the time of arthroscopy. Arthroscopic and histological scores were assigned to each synovial exploration and sample according to a previously established scoring system.

Results:

Macroscopic and histological scores of group 2 were significantly higher than group 1. Arthroscopic and histological evaluations were only significantly correlated for group 1. Cellularity significantly correlated to arthroscopic scores for groups 1 and 2 but did not correlate with histological scores. Principal component analysis showed that the highest discrimination between group 2 and the others was due to the high concentration of IL6 and IL1β. In addition, group 2 presented significantly higher concentrations of IFNγ and IL10. A significantly higher concentration of TNFα was found in group 2 compared to group 1.

Conclusions:

Although synovial cellularity provides valuable information about the condition of the joint, histological evaluation in synovial sepsis should be considered as an additional modality for accurate diagnosis. Concentrations of IL6, IL1β and TNFα could serve as synovial biomarkers of septic involvement.