LAUSR

Abstract Background Plantar osteochondral fragments (POF) are common but their effect on joint health of young Standardbreds in race training is largely unknown. Objectives Evaluate the inflammatory effects of POF in metatarsophalangeal joints of young Standardbreds as a step towards developing evidence‐based recommendations for surgical removal. Study design Cohort study. Methods Forty‐nine Standardbred horses (age 11‐33 months) presented for surgical removal of POF from 56 metatarsophalangeal joints. Synovial tissue collected at arthroscopy was subjected to histopathology. IL‐1β, TNF‐α, and PGE‐2 were measured in synovial fluid using ELISA. Digital arthroscopy images were scored for inflammation. Racing performance data were retrieved from a public database. Results Median time in race training prior to surgery was 8 weeks (IQR 4‐12; range 0‐40). There was minimal evidence of synovial inflammation as assessed by histopathology (median total score 2/20, IQR 0‐2, range 0‐5) or arthroscopy (median average total score 2.67/15, IQR 1.79‐4, range 0‐8.83). IL‐1β was not detected in any sample. TNF‐α (median 0 pg/mL, IQR 0‐0) and PGE‐2 (median 56.6 pg/mL, IRQ 40.5‐99.8) were measured at low levels. Weeks in training prior to surgery was associated with the number of starts in the season after surgery (incidence rate ratio 1.02, 95% CI 1.00, 1.04, P = .03). Main limitations Small sample size from a single breed with a relatively short training time prior to surgery. Conclusions There was minimal evidence of synovial inflammation in the metatarsophalangeal joints in this population of young Standardbred horses with POF. It is possible that POF may result in a different inflammatory response than other fragments because they are generally well‐embedded in situ. These findings suggest that, in Standardbreds, race training can commence several weeks prior to surgical removal of POF with minimal detrimental effects on joint health, although further investigation of long‐term effects of POF on joint health is warranted.