Evaluation of changes in X-ray, blood samples and synovial fluid in dogs with cranial cruciate ligament disease induced osteoarthritis

Abstract

Cranial cruciate ligament disease (CCLD) induced osteoarthritis (OA) has often been viewed as a degenerative non-inflammatory disease, there is now clear evidence that synovitis plays important role in OA pathogenesis [1]. The most accurate method to confirm synovitis is the analysis of the physical, chemical and citological properties of synovial fluid. Biomarkers such as C-reactive protein (CRP) and cytokines, especially TNF-α and IL-6 are important to assess potential articular cartilage damage and its progression [1, 2]. In keeping with the Starling–Landis theory, it was further suggested that changes in synovial fluid inflammatory biomarkers levels could influence levels found in the blood [3]. The degree of effusion and osteophyte formation of the stifle joint is evaluated in the radiographs, and the tibial plateau angle (TPA) was measured. The main indicators determining the physical (amount, color, turbidity, viscosity), chemical (mucin clot test, protein content) and cytological properties of the synovialfluid were determined. CRP concentration was determined with a FUJIFILM DRI CHEM NX600 biochemical blood test analyzer. The concentration of the cytokines IL-6 and TNF-α was determined in blood plasma samples by enzyme-linked immunosorbent assay (ELISA) using commercial ELISA kits. The formation of the 2 degree osteophytes was found in 90.0 % of all dogs and 46.7 % had an average degree effusion of stifle joint. Morphometric measurements showed that mean TPA was 25,71º (SD-3,60,95% IP 24,36-27,05), which was 1.2 times higher than the maximum allowable TPA mean for healthy dogs (20.6 º) (p>0.05). Synovial fluid viscosity was 2.4 cm (SD-0.96, 95% CI 2.0-2.8) (p<0.05). In the 66.7 % of synovial fluid samples, the amount of protein was higher than 3.0 g/dl and varied from 2.0 g/dl to 9.5g/dl (median-3.4 g/dl). 97.7 % cells of synovial fluid consisted of oval-nucleated macrophages with slightly vacuolated cytoplasm and 1.9 % was neutrophils, with a segmented nucleus and light blue stained granular cytoplasm. 73.3 % of all dogs did not have systemic inflammation (CRP ≤ 7 mg/dl). The concentration of TNF-α in dogs with osteoarthritis was 20,608 pg/ml (SD-20,8, 95% IP 3,218-37,999) and was 1.98 times higher than in clinically healthy dogs p<0.05). IL-6 levels in dogs with CCLD induced OA ranged from 0.196 ng/ml to 0.448 ng/ml (median 0.229 ng/ml) (p>0.05). In order to more accurately determine and follow the progression of OA in clinical practice, we recommend to perform an X-ray examination, cytological evaluation of the synovial fluid, determination of the viscosity and protein content of the synovial fluid.