The difference in exercise history suggests there’s a difference in how the two types of condylar fractures develop
Paulick Report Staff
Jan 27, 2025
A new study published in the Equine Veterinary Journal has shown a correlation between a Thoroughbred racehorse’s exercise history and the location of subsequent condylar fracture. This suggests that there’s a difference in how the two types of condylar fractures develop, and thus, may suggest different risk factors for each.
The accumulation of “high-speed furlongs” in Thoroughbred racehorses, and the results that accumulation has on risk for lower-limb fractures, has been a popular topic of study since Dr. Susan Stover’s article Journal of Orthopedic Research in March of 2022, titled “Exercise history predicts focal differences in bone volume fraction, mineral density and microdamage in the proximal sesamoid bones of Thoroughbred racehorses.”
In that 2022 study, researchers examined racehorses euthanized due to proximal sesamoid bone fractures versus those euthanized for injuries unrelated to the sesamoid bone. They found that horses suffering a proximal sesamoid bone fracture “participated in over twice as many lifetime works and races, accumulated nearly twice the lifetime work and race distance, had over twice as much time in training since last layup, and performed nearly twice the distance, events, and works each month, 1–12 months before death.”
The newer study, published in the January 2025 edition of the Equine Veterinary Journal by Stover and Drs. Thomas Bergstrom, Mathieu Spriet, Ryan Carpenter, and Kevin Jacques, looks at condylar fractures along a horse’s cannon bone. Two primary locations were identified for the fractures: either along the parasagittal groove, nearer the center of the cannon bone, or abaxial to the PSG, nearer the outside of the cannon bone.
While the study found no statistical differences in the return-to-racing prognosis or subsequent success between the two fracture groups, differences were found in the horses’ exercise histories.
Horses with non-PSG fractures were found to have accumulated “significantly more races, works, and total officially recorded high-speed furlongs than horses with PSG fractures,” the authors report, which is “consistent with excessive workload, likely leading to the inability for bone tissue to recover from accumulated microdamage.”
The highest discrepancies were found between five and six months before fractures occurred, a timeframe which authors speculated “could initiate a series of microscopic events in the condyle that induce an inability of the microdamage accumulation to be repaired.”
Horses which suffered PSG fractures were “exposed to a less extensive exercise regimen and therefore may have less subchondral bone modelling and resorption.” These horses showed more workouts during active periods, but spent more time in layup and had fewer high-speed furlongs in the month before fracture. The authors suggest these findings “may be related to insufficient adaptation to training and/or bone density gradients in this region.”
Interestingly, 13 of the 82 horses in the study suffered condylar fractures before their first start; all 13 were in the PSG category, leading authors to suggest that possible factors may be “developmental abnormalities and/or genetic predisposition.”
The full study is available here.
