Catastrophic biaxial proximal sesamoid bone fractures in UK Thoroughbred races (1999-2004): horse characteristics and racing history.

The research study investigates catastrophic biaxial proximal sesamoid bone fractures (PSBF) in racehorses in the UK, focusing on the relationship between horse characteristics, type of race and racing surface, incidence and risk of PSBF. Results suggest an association between racing surface and occurrence of PSBF, with higher incidences in flat races on all-weather surfaces.

Research Methodology

• The research was done prospectively from February 1999 to December 2004, whereby distal limbs were collected from all racehorses that suffered catastrophic fractures during races at all 59 racecourses in the UK.
• Post-mortem investigations were carried out to identify the anatomical location and type of fracture.
• Information on the horse, its racing history, race and racecourse details were gathered.
• Characteristics of horses sustaining PSBF were then described, and the incidence and relative risk (RR) of PSBF in different types of racing were calculated.

Research Findings

• The study observed that 31 horses suffered PSBF during the research period.
• The incidence of PSBF in all race types was found to be 0.63 per 10,000 starts.
• The highest incidence of PSBF was observed in flat races conducted on all-weather surfaces, with the rate being 1.63 per 10,000 starts, making the relative risk 4.4 times higher compared to turf flat racing.
• The affected horses were, on average, 5.6 years old and had participated in around 28 races at the time of fracture.

Conclusions

• The research concludes a strong correlation between the type of racing surface and the occurrence of PSBF.
• Horses participating in flat races on all-weather surfaces had an increased risk of encountering PSBF.
• Most fractures were observed in experienced horses with several race starts, indicating a low occurrence of fractures within the horse’s first racing season.
• In light of these findings, the researchers suggested further studies targeting the identification of potential underlying pathologies of such fractures.
• Considering the low incidence of PSBF, the researchers also pointed out that epidemiological studies aimed at identifying risk factors for PSBF in the UK racing population would require many cases acquired over a significant number of years.