Influence of shoeing on ground reaction forces and tendon strains in the forelimbs of ponies.

This research study investigates how different types of horseshoes influence the stress or strain placed on the various tendons in a pony’s forelimb during walking. The study found that different shoe types significantly altered the level of strain in ponies’ tendons, which correlated with changes in the force exerted on the pony’s hoof by the ground.

Study Design and Methodology

• The study involved five ponies whose superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), an accessory ligament (the inferior check ligament [ICL]) and the suspensory ligament (SL) in the right forelimb were all monitored for strain.
• Mercury-in-silastic strain gauges were implanted into the ponies to measure strain a few hours after implantation. These measurements were recorded during a walk while the ponies wore four different types of shoe arrangements: normal flat shoes, egg-bar shoes, shoes with a 7-degree angular increase at the heel (heel-wedge) and shoes with a 7-degree angular decrease at the toe (toe-wedge).
• Additionally, ground reaction forces, or the force exerted by the ground on the pony’s hoof, were monitored with all four shoe types preoperatively and postoperatively with flat shoes.

Findings

• The strain patterns for the SDFT, DDFT and SL all showed a rapid increase at the beginning of the stance phase (when the hoof is on the ground bearing weight), followed by a steady level with either a slight increase or decrease, before finally rapidly decreasing at the end of the stance phase.
• The point of maximal strain varied between different tendons and ponies. The SDFT experienced maximal strain in the first half of the stance phase in all ponies, while the DDFT and SL experienced maximal strain in either the first or second half of the stance phase. The ICL experienced maximal strain in the second half of the stance phase in all ponies.
• Both the type of shoe and the orientation of the shoe (e.g., heel-wedge or toe-wedge) significantly altered tendon strain levels. For example, applying an egg-bar shoe significantly decreased the strain in the DDFT by 0.13%, but increased the strain in the SL by 0.22%.

Conclusion

• The research results provide evidence that the choice of horseshoe can significantly affect the strain experienced by a pony’s tendons during walking.
• Moreover, changes in tendon strain associated with different types of shoes correspond to changes in the calculated torque of the ground reaction force on the hoof, suggesting a direct relationship between these factors.