Effect of Perineural Anesthesia on the Centre of Pressure (COP) Path During Stance Phase at Trot in Sound Horses.

The research tested whether temporarily numbing the nerves of a horse’s leg influences the pressure pattern of the horse’s hooves during a trot. Results showed no significant changes, suggesting that sudden changes in a horse’s gait after such anesthesia should be carefully examined.

Objective of the Study

• The study aimed to investigate how temporary loss of touch perception (proprioception) in a horse’s hoof affects the path of the Centre of Pressure (COP) during the standing phase of a trot. The COP is a measure used to evaluate the pressure applied by the hoof on the ground during various phases of walking or trotting.

Methodology

• 10 horses were initially evaluated using the ‘Equinosis Q System’ to ensure that they were not lame and could trot normally.
• A portable pressure measuring system with pressure-sensitive foils was placed directly under both front hooves. These foils would measure the pressure and path of the COP.
• Measurements were taken before and after the horses were subjected to perineural anesthesia of the palmar digital nerves. This type of anesthesia temporarily numbs the nerve and was used to simulate the loss of proprioception in the horse’s foot.
• Further, the individual COP paths of both forelimbs were assessed before and after nerve block injections were applied to the abaxial sesamoid nerves on one or both sides.

Results and Findings

• The study found that the individual COP path during the stance phase is highly repeatable for each horse and limb. This means that there is minimal to no change in the pressure distribution and path each time a horse places its hoof on the ground.
• Neither the location of initial hoof-ground contact, nor the COP during mid-stance and breakover phases were affected by the temporary loss of sensory feedback from the foot after the nerve was numbed (either on one or both the sides).

Conclusions

• The results show that anesthesia of the foot with an abaxial sesamoid nerve block does not alter the COP of the horse’s foot during the stance phase at a trot.
• The conclusion derived from these findings is that any sudden changes in a horse’s gait after the application of perineural anesthesia should be assessed with caution. Therefore, further clinical investigations are recommended if such changes are observed.