Frequency distributions of 174 fractures of the distal condyles of the third metacarpal and metatarsal bones in 167 Thoroughbred racehorses (1999-2009).

This study investigates the frequency and morphology of fractures in the distal condyles of the third metacarpal and metatarsal bones in Thoroughbred racehorses over a ten year period. It reveals possible changes in fracture occurrence over time and offers new insight into the causes and location of these fractures.

Methodology

• The research employed a retrospective analysis of case records at Newmarket Equine Hospital.
• The study focused on horses with fractures of the distal condyles of third metacarpal/metatarsal bones seen over the last 10 years.
• The current series of fractures was compared with a prior series from the UK; the authors also analyzed grouped data from UK and USA studies.

Results

• A total of 174 fractures were identified in 167 racehorses.
• There was a significantly lower proportion of medial condylar fractures in the current series than in a similar population from 17 years earlier.
• Fractures originating more abaxially (away from the midline of the body) were found to be shorter and a significant proportion of lateral condylar fractures occurred outside of the condylar groove (a depression or groove at the end of the bone).
• There was also an observed seasonality of fractures of the lateral condyles in 2-year-old horses, but not so in older horses or in horses with medial condylar fractures.

Conclusions

• Approximately 50% of fractures in the current series cannot be explained by existing theories of aetiopathogenesis (causes and development of diseases), which generally assert that fractures usually occur within the condylar groove, as a result of cumulative fatigue and failure of bone adaptation.
• The study suggests that a separate cause may be responsible for a proportion of condylar fractures found in racehorses.
• The change in number of medial condylar fractures may be attributable to the introduction of artificial racing and training surfaces, and may also reflect demographic changes in horses racing since the UK rolled out year-round ‘all-weather’ racing.