Kinetics and kinematics of the equine hind limb: in vivo tendon strain and joint kinematics.

This research investigated the kinematic and kinetic features of equine hind limbs, specifically focusing on how different tendons in the hind limb experienced strain during normal walking. Using strain gauges implanted on ponies, it was found that varying levels of strain were recorded for different tendons. The study also explored how walking impacted the distance between the origin and insertion of these musculotendinous structures.

Methodology

• The team carried out the study by implanting strain gauges, made from silicone rubber tubes filled with mercury, into the suspensory ligament and some tendons in the equine hind limb.
• The study was conducted in vivo, meaning the investigators studied the ponies in their natural form, undisturbed by external influences.
• Their primary focus was to measure the tendon strains in the suspensory ligament and the deep digital flexor, superficial digital flexor, and long digital extensor tendons.
• The relationship between the strain gauge signals and the tendon strains was determined by performing tension-strain tests on the respective tendons after the ponies had died.

Results

• During ordinary walking, they recorded maximum tendon strain values of 3.1% for the suspensory ligament and 3.4%, 2.3%, and 0.3% respectively for the deep digital flexor, superficial digital flexor, and long digital extensor tendons.
• These strains which are essentially the elongations over initial length, were measured relative to the length of the structures at first ground contact.
• The distances from origin to insertion of these musculotendinous structures (which are essentially the connection points of the muscles with the tendons) were also observed.
• The maximum increase in these distances during walking was 3.1% for the suspensory ligament and 2%, 1.6%, and 1.5% for the deep digital flexor, superficial digital flexor, and long digital extensor tendons, respectively.

Interpretation of the Results

• The variations in the observed strain when comparing the performing musculotendinous structure and its actual tendon were found to be linked to the contraction or relaxation of the muscle.
• Therefore, the strain and distances observed in this study are the natural effects of the walking movement on the musculotendinous structures and tendons of the equine hind limb.

The knowledge derived from this study can help better understand the biomechanics involved in equine movement, potentially informing treatments or strategies for preserving the health and performance of these animals.