PSI-18 Intra-articular triamcinolone acetonide administration does not affect microbial culture or synovial fluid volume in young, exercising Quarter Horses

Abstract Intra-articular corticosteroids (IAC) are administered to horses experiencing joint inflammation, at times with a concurrent articular antibiotic for prophylaxis. However, information regarding the biologic effects of IAC and potential for microbial contamination in IAC-administered joints is limited in young, exercising horses. The objective of this study was to evaluate the impact of IAC on traditional microbial culture, synovial fluid (SF) volume, and the presence of IAC; hypothesizing negative microbial culture, no change of SF volume, and detection of IAC in SF post-administration. To test this, 2-yr-old Quarter Horses {n = 24; body weight (BW) = 409 ± 6 kg; 825 ± 21 d of age; 12 fillies, 12 geldings) were stratified by BW, age, and sex, and randomly assigned to 1 of 3 treatment groups for a 56-d trial. Horses were housed individually in stalls with runs and fed concentrate offered at 0.75% BW/d split evenly every 12 h with ad libitum Coastal bermudagrass hay and water. Every 21 d, BW and body condition score (BCS) were recorded, and concentrate was adjusted accordingly. Horses were exercised 5 d/wk, up to 45 min/d in a progressive workload using a free-stall exerciser. Blood was collected post-exercise during wk 1, 4, and 7 via jugular venipuncture and lactate (BL) was measured to monitor increasing workload. Intra-articular treatments consisted of 0 mg (CON; n = 8), 6 mg (CORT6; n = 8), or 12 mg (CORT12; n = 8) of triamcinolone acetonide (TA). On d 0, treatments were administered in one randomly selected radiocarpal joint per horse. Following aseptic preparation, SF from both radiocarpal joints was collected before administration (pre), and on d 7, 14, 28, and 56. Volume of SF was recorded, and standard microbial culture and detection of TA were performed by a commercial laboratory. Data were analyzed using PROC MIXED (BW, BCS, BL, SF volume) and PROC GLM (TA) of SAS. For SF volume, data from the contralateral radiocarpal joint were used as a covariate. Horses increased BW and BCS over time (P ≤ 0.01) across treatments. Post-exercise BL increased from wk 1 to 4 and remained increased through wk 7 (P < 0.01). Microbial culture for all horses and time points were negative. Concentration of TA was not evaluated on d 7 due to limited SF volume, but TA was detected on d 14 and concentration did not differ between CORT6 and CORT12 (P = 0.13). Recorded SF volume did not change from d 0 (pre) to 7 but increased to d 56, regardless of treatment (P < 0.01). These results indicate that, based on standard culture, TA administration did not result in positive microbial culture, or decrease SF volume in young horses undergoing regular exercise, however, TA was detectable to d 14.