Induction of Noninflammatory Pain in an Experimental Foot Lameness Model in Horses.

This study investigates how the application of a heart bar shoe (HBS) lameness model in horses, typically treated with nonsteroidal anti-inflammatory drugs, does not induce inflammation as evident from several markers, implying the pain is mechanical rather than inflammatory.

Study Overview

The experiment was performed on five adult horses from a university herd. Researchers used a custom HBS on each horse’s left front foot, aiming to achieve a specific lameness score. The investigation was set to explore if the HBS shoe induces inflammation in the horse’s foot by measuring various inflammatory markers before and after the induction of lameness.

Procedure and Observations

• In this experiment, the lameness was induced to a degree that meets the standards of the American Association of Equine Practitioners Lameness Score of 4.
• Before inducing lameness and at intervals of 1,3 and 13 hours after, several measurements were taken to check for any signs of inflammation. These included the concentration of serum amyloid A (a marker of inflammation) in the bloodstream, levels of tumor necrosis factor alpha and prostaglandin E2 (functional mediators of inflammation) in the local veins, and the temperature of the foot.
• Results indicated that there was no significant increase in the levels of serum amyloid A, tumor necrosis factor alpha, or prostaglandin E2 in the horses that were made lame using the HBS technique.
• Interestingly, there was an observation of higher temperatures in the foot with the heart bar shoe (dorsal coronary band) immediately after and an hour after the lameness induction. But, no temperature difference was observed after 3 or 13 hours, suggesting no continuous inflammatory response.

Conclusions and Implications

• This study concludes that the use of the HBS model does not induce inflammation in horses based on the given inflammatory markers.
• These findings imply that the model induces mechanical pain rather than inflammatory pain in horses.
• The outcome of this research could influence how analgesic drugs are assessed in future studies, particularly in models applying techniques similar to the HBS, as current treatment strategies leveraging nonsteroidal anti-inflammatory drugs may not be addressing the actual type of pain involved.