RESUMEN
BACKGROUND: Intrasynovial corticosteroid injections are commonly used in the treatment of equine orthopaedic disease, but corticosteroid administration is widely considered a risk factor for the development of laminitis. Despite a list of putative mechanisms and a number of case reports of steroid-induced laminitis, no case-control or cohort studies investigating the association between use of intrasynovial corticosteroids and acute laminitis have been published. OBJECTIVES: To quantify the risk of laminitis posed by intrasynovial triamcinolone acetonide (TA) administration in a mixed population of horses. STUDY DESIGN: Retrospective observational cohort study. METHODS: Clinical records of horses registered with one large UK equine practice were reviewed retrospectively to identify all horses receiving intrasynovial TA treatment between 1 January 2007 and 31 December 2017. A total of 1510 horses were selected and records investigated for incidence of laminitis over a 4-month period following treatment. For each TA-treated horse, an untreated horse, individually matched by age, sex, date of treatment and client type, was selected from the clinical records. Untreated horses were then investigated for laminitis over the same 4-month period. Data were analysed in a 2 × 2 contingency table using Fisher's exact test. RESULTS: A total of 489 horses were lost to follow-up and 55 horses were excluded, leaving 966 treated and matched, untreated horses. The incidence of laminitis over the 4-month study period in both groups was identical: 3/966 horses (0.31%) (95% C.I. [0.08%, 0.91%]), equivalent to 0.93 cases per 100 horses per year (P > .9). MAIN LIMITATIONS: Retrospective study; large proportion (489/1510) of horses lost to follow-up; large proportion of study population were racehorses; selection method resulted in disproportionate selection of horses born before 2013; similar incidence between groups may reflect existing risk-based selection by clinicians. CONCLUSIONS: intrasynovial triamcinolone acetonide administration does not increase the risk of laminitis in this study population.