Effect of repeated arthrocentesis on cytologic analysis of synovial fluid in healthy horse

Introduction. Arthrocentesis is a common practice used for the diagnosis and therapy of many articular pathologies. The aim of the present work was to evaluate the influence of repeated arthrocentesis on synovial fluid composition in healthy horses. Materials and methods. Approval to conduct this study was obtained from the Ethics Committee on Animal Experimentation of the University of Pisa n. 14875 – 20/11/12). Four horses not affected by muscoloskeletal diseases were submitted to repeated arthrocentesis from both the intercarpal (IC) joints. In particular, the right IC joint was sampled at Time 0 (T0), at 2 (T2), 7 (T7) days and then every week for 3 times (T14, T21, T28, respectively) after T0, while the left IC joint was sampled at T0 and then every 10 days for two times (T10 and T20, respectively) after T0. An arthrocentesis was also performed on both IC joints 60 days (T60) after T0. Arthrocentesis were always performed by the same operator (R.F.B.). The synovial fluid samples were collected in EDTA and processed within 1 hours to evaluate: 1) total protein (TP) concentration by a rephractometer (Mahaffey, 2002); 2) total WBC count by an automatic hematology analyzer (Lasercyte®, Idexx, USA) with hyaluronidase pretreatment (Moreno et al., 2000; Eckmann et al., 2010) to reduce the viscosity; 3) differential leukocyte count after cytospin preparation (1500 gpm, 5’) (Cytofuge 2, StatSpin, USA) to improve smear’s quality (Moreno et al., 2000), a modified Romanowsky staining (Diff Quik®, Dade Spa, Milano, Italia) and microscope evaluation at 100X. Data distribution was performed with KS test; Anova for repeated measures and Bonferroni test as post hoc were applied to verify differences related to sampling times. Significative level was set at p<0.05. Results. Data were expressed as mean±standard deviation. The total WBC count did not change over time as well as the percentage of lymphocytes, eosinophils and neutrophils, while a variation over time was observed for monocytes and total protein concentration. Both decreased from T0 to T14 (right IC joint) and T10 (left IC joint), then rised again over time till T60 with values similar to T0.