Characterization of a reversible lameness model in the horse

Objective: Characterization of a model of reversible foot lameness in the horse. Methods: Both forelimb hooves were fitted with a circumferential clamp. After three baseline measurements utilizing a force platform, one clamp was tightened to induce a grade 2.5/5 lameness and left in place for 120 hours. Serial heart rate and force platform measurements were obtained and the asymmetry index was calculated. After 120 hours, the clamp was released and force platform data recorded until the horse returned to soundness. The procedure was repeated for the opposite forelimb. The responses of treatment compared with the control for each outcome were analysed using linear mixed models. Time, limb (left or right), order of treatment, and interaction between time and order were used as fixed effects, whereas horse and limb were used as random effects. Results: There was a significant increase in lameness associated with time and treatment order, where the second limb treated was more lame, based on the force platform data. The heart rate increased significantly with time and was significantly greater while the first limb was being treated. There was a significant effect of time on the increased subjective lameness score. Clinical significance: The lameness was present throughout the measurement period, though the level of lameness lessened with time. The model may be applicable for evaluation of mechanisms to treat pain in the horse. The reason for the difference in treatment order needs to be identified.