Effect of differences in tendon properties on functionality of the passive stay apparatus in horses.

This research article explores how differences in horse tendon properties influence the function of the passive stay apparatus within horses, focusing on non-dwarf Friesians, dwarf Friesians, and ponies.

Research Methodology

• The study involved analyzing five forelimbs each from non-dwarf Friesians, dwarf Friesians, and ponies. The forelimbs were harvested specifically for this research, and load testing was conducted to investigate the functionality of the passive stay apparatus.
• The tendons responsible for maintaining stability in the distal part of the limb, including the superficial digital flexor tendon, deep digital flexor tendon, and tendo interosseus (also known as the suspensory ligament), were isolated for further study.
• The researchers collected force-elongation data from these tendons. They also measured bone lengths, initial tendon lengths, and initial tendon cross-sectional areas, and calculated the Young’s modulus for each tendon. The Young’s modulus gives a measure of the stiffness of an elastic material and is used in engineering and physics.
• A model was used to evaluate whether joint angles could be explained by the four measured factors alone.

Research Findings

• The results showed that dwarf Friesians could not stand passively under loading (an applied force) as the tendons preventing overextension of distal limb joints were overly long and compliant, meaning they allowed for too much stretch. This resulted in overextension of the joints.
• Non-dwarf Friesian’s tendons exhibited properties that were intermediate between those of ponies and dwarf Friesians. This suggests there might be breed-specific variations in tendon properties.
• These findings suggest that the dysfunction of the passive stay apparatus in dwarf Friesians could be attributed to differences in the structural and material properties of the tendons, leading to excessive joint extension under load.

Significance of the Research

• The research advances our understanding of how tendon properties can influence load failure of the passive stay apparatus in horses, enlarging our knowledge about the functionality and requirements of the passive stay apparatus.
• The results from this study could be leveraged to develop better breeding or therapeutic programs to mitigate joint over-extension in specific horse breeds such as the dwarf Friesians.