Effect of arthroscopic lavage and repeated through-and-through joint lavage on systemic and synovial serum amyloid A concentrations; as well as total protein concentrations, nucleated cell count and percentage of neutrophils in synovial fluid from healthy equine joints

Abstract

This research evaluated serum amyloid A (SAA) concentration in synovial fluid of healthy horses as a potential marker for use in the diagnosis and monitoring of horses with septic arthritis. The first study evaluated the effect of arthroscopic lavage of healthy joints on concentrations of systemic and synovial SAA; as well as total protein concentration, nucleated cell count and percentage of neutrophils in synovial fluid. The second study, evaluated the effect of repeated through-and-through joint lavage on SAA in systemic blood and SAA, total protein, nucleated cell count and percentage of neutrophils in synovial fluid from healthy joints. In the first study, middle carpal joints of 6 horses were randomly assigned to one of the following treatments 1) arthrocentesis (controls) or 2) arthroscopic lavage. A washout period of 30 days was allowed in between treatments. Synovial fluid and blood samples were collected at 0, 24, 48, 72, 96 and 120 h. Measurements included SAA in blood and synovial fluid, and total protein, nucleated cell count and percentages of neutrophils in synovial fluid. In the second study, one tarsocrural joint was randomly assigned to receive repeated through-and-through joint lavage at 0, 48 and 96 h in 6 horses. Synovial fluid and blood samples were collected at 0, 24, 48, 72, 96 and 120 h. Measurements included SAA in blood and synovial fluid, and total protein, nucleated cell count and percentages of neutrophils in synovial fluid. For this study, synovial fluid samples collected at time 0 were considered as control values. After arthroscopic lavage and repeated through-and-through joint lavage, systemic and synovial SAA did not increase from baseline values (except for systemic SAA at 24h after arthroscopic lavage and in controls). Total protein values were significantly increased at all time points after arthroscopic and through-and-through joint lavages (except at 96h on both lavage procedures) but not in controls. With both lavage procedures, nucleated cell count significantly increased from baseline values at all time points (except at 96h after through-and-through joint lavage). Percentage of neutrophils was significantly increased after arthroscopic lavage at all time points and only at 24h in controls; however, the percentages of neutrophils were not significantly increased after repeated through-and-through joint lavage. Synovial SAA was not affected by arthroscopic or repeated through-and-through joint lavage; however, synovial total protein and nucleated cell counts were significantly increased. Synovial SAA may be a valuable inflammatory marker that is not affected by procedures as arthroscopic or repeated through-and-through joint lavage in horses. Further validation of synovial SAA as a marker for evaluating the progression of septic joints while treatment is installed is warranted.