Impact of ununited plantar eminence of the first phalanx on early racing performance in North American Standardbreds.

UPE correlates with reduced 3-year-old racing performance in Standardbreds, though concurrent DOD lesions confound independent significance.

This retrospective cohort study examined 1,897 yearling North American Standardbred horses to determine the prevalence and clinical significance of ununited plantar eminence (UPE) of the first phalanx. UPE was identified in 74 horses (3.9%), with 67.6% of affected horses concurrently presenting developmental orthopedic disease (DOD) lesions, particularly plantar osteochondral fragments. Affected horses were matched with unaffected siblings and compared using non-parametric statistical tests. At 2 years of age, no performance differences were observed between groups. However, as 3-year-olds, affected horses demonstrated significantly reduced racing performance, including fewer race starts and lower earnings compared to unaffected siblings. The study indicates that while UPE is an uncommon finding, it may have negative implications for long-term athletic performance in Standardbred racehorses. However, the frequent association with other DOD lesions complicates interpretation of UPE's independent clinical significance. The results suggest UPE warrants monitoring during performance assessment, though its isolated prognostic value remains unclear.

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