Modelling the effect of race surface and racehorse limb parameters on in silico fetlock motion and propensity for injury.

The research article presents a computational model to analyze the impact of racehorse surface and limb characteristics on the movement of the metacarpophalangeal joint (fetlock) and the risk for injury. The model identifies surface layer depth as the primary factor influencing the range of fetlock motion, a key driver of common racehorse injuries.

Understanding the Research

• This research focuses on understanding the potential risks to a racehorse’s metacarpophalangeal joint, commonly referred to as the fetlock, which is the most frequent site of injury in racehorses. These injuries are often associated with extreme dorsiflexion, or backward bending, of the fetlock.
• One of the major factors contributing to these injuries is the mechanics of the race surface which the horse runs on as it influences the forces exerted on the horse’s limbs and how those limbs move in response.
• The researchers endeavored to determine how changes in race surface and the horse’s limb parameters can affect the movement of the lower limb region. To achieve this, they used a computational model of both a racehorse and the race surface.

Research Methodology

• A sensitivity analysis was conducted to see how changes in different parameters like the average vertical stiffness of the surface, depth and linear stiffness of the upper layer (cushion), horizontal friction, and the mechanics of ligaments and tendons affect the fetlock motions during galloping.
• The position of the fetlock at the time of heel strike was also considered as a parameter in the simulations.

Research Findings

• The most significant change in fetlock motion was due to the depth of the upper layer of the racing surface- shallow depths resulted in greater dorsiflexion of the fetlock.
• Changes in other parameters like the mechanics of the lower surface layer (e.g., base or pad) and the stiffness of ligaments and tendons in the palmar region resulted in less significant changes in the movement of the fetlock.
• Horizontal friction and the position of the fetlock at heel strike had negligible effects on the fetlock motion (<1° change).

Conclusions and Implications

• While the study reflects the physiology of one horse, anatomical differences among horses may lead to variations in the degree of limb flexion, but they would likely respond similarly to changes in surface mechanics.
• The research indicates that the parameters of the race surface that can be altered through maintenance have a greater impact on fetlock motion than other studied factors.
• This finding suggests that careful management of race surface design, especially the depth of the upper layer, could potentially reduce the incidence of injuries.