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

Overview

• This study investigated the occurrence of ununited plantar eminence (UPE) in the first phalanx bone of North American Standardbred horses and examined how UPE affects early racing performance, particularly at ages 2 and 3 years.

Background and Objectives

• UPE is a specific orthopedic condition involving the first phalanx (P1) bone in horses.
• Standardbred horses are a popular breed used in harness racing, and understanding orthopedic conditions that affect their racing ability is important.
• The research aimed to:
• Determine how often UPE occurs in yearling Standardbred horses in North America.
• Evaluate the relationship between UPE and early racing performance, especially the differences in performance at ages 2 and 3 years.
• Assess the impact of other factors such as sex, gait type, and the presence of other developmental orthopedic disease (DOD) lesions on the performance of horses with UPE.

Methods

• This was a retrospective cohort study using existing records and imaging data.
• Data was collected from imaging records of 1897 yearling Standardbred horses.
• Screening images were examined to identify UPE and other orthopedic abnormalities.
• Information on sex, age, sire (father horse), gait type (trot or pace), and racing performance data was obtained from the United States Trotting Association.
• Affected horses (those with UPE) were compared to their unaffected siblings to reduce genetic and environmental confounding factors.
• Statistical analyses included non-parametric tests to compare performance data and regression analyses within the affected group to assess influences of sex, gait, and presence of other DOD lesions.

Key Findings

• The prevalence of UPE in the studied population was 3.9% (74 out of 1898 horses).
• A majority (67.6%) of horses with UPE also had other concurrent orthopedic issues, most commonly plantar osteochondral fragments (small bone/cartilage fragments in the plantar region).
• At the age of 2 years, there was no significant difference in racing performance outcomes (such as starts, finishing positions, or earnings) between horses with UPE and their unaffected siblings.
• At 3 years of age, horses affected by UPE were less likely to have started racing, had fewer race starts, and earned less prize money compared to unaffected siblings.

Conclusions and Implications

• UPE is a relatively uncommon orthopedic lesion in yearling Standardbred horses but is commonly seen alongside other developmental orthopedic diseases.
• The lack of performance differences at 2 years suggests that UPE may not initially impair early racing ability or that early performance impacts are masked by other factors.
• The reduced racing participation and earnings at 3 years indicate that UPE is associated with decreased longer-term athletic performance or durability.
• As UPE frequently co-occurs with other DOD lesions, it’s difficult to isolate its specific clinical significance; it may be one component in a broader orthopedic disease process impacting racing capacity.
• This information is valuable to veterinarians, trainers, and breeders for assessing prognosis and training decisions in Standardbreds with UPE.