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Abstract

Objective—To evaluate patterns of digital cushion (DC) displacement that occur in response to vertical loading of the distal portion of the forelimb in horses.

Sample Population—Forelimbs from 10 horses with normal feet.

Procedure—Patterns of DC displacement induced by in vitro vertical limb loading were determined. Loadinduced displacement of the DC was defined as the magnitude and direction of displacement of 6 radiodense, percutaneously implanted markers in specific regions of the DC. The effects of solar support and nonsupport on displacement of the DC were compared.

Results—Regional displacement of the DC occurred principally along distal and palmar vectors in response to vertical loading. Medial or lateral abaxial displacements were variable and appeared to be dependent on response of the limb to the applied load. Displacement of the DC was not affected by the degree of solar support.

Conclusions and Clinical Relevance—Data indicated that the biomechanical function of the DC is to act as a restraint to the displacement of the second phalanx or as a passive structure that allows flexibility of the caudal two thirds of the foot. Results did not indicate that the DC provides a force that induces displacement of or an active restraint against outward displacement of the hoof wall capsule. (Am J Vet Res 2005;66:623–629)

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in American Journal of Veterinary Research

Abstract

Objectives—To compare limb-load distribution between horses with and without acute or chronic laminitis.

Animals—10 horses with carbohydrate-induced acute laminitis, 20 horses with naturally occurring chronic laminitis, and 20 horses without foot abnormalities (controls).

Procedures—Limb-load distribution was determined, using a custom-designed system that allowed simultaneous quantification of the mean percentage of body weight voluntarily placed on each limb (ie, mean limb load) and the SD of the mean load over a 5- minute period (ie, load distribution profile [LDP]). Load distribution profile was used as an index of frequency of load redistribution.

Results—Mean loads on fore- and hind limbs in control horses were 58 and 42%, respectively, and loads were equally and normally distributed between left and right limbs. In addition, forelimb LDP was greater, compared with hind limbs, and was affected by head and neck movement. In comparison, limb-load distribution in horses with chronic laminitis was characterized by an increase in the preferential loading of a forelimb, a decrease in total forelimb load, and an increase in LDP that was correlated with severity of lameness. In horses with carbohydrate-induced acute laminitis, mean limb loads after onset of lameness were not different from those prior to lameness; however, LDP was significantly decreased after onset of lameness.

Conclusion and Clinical Relevance—Quantification of limb-load distribution may be an applicable screening method for detecting acute laminitis, grading severity of lameness, and monitoring rehabilitation of horses with chronic laminitis. (Am J Vet Res 2001; 62:1393–1398)

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in American Journal of Veterinary Research

Abstract

Objective—To determine whether systemic immunologic hyperreactivity exists in horses with chronic laminitis, compared with responses for nonlaminitic horses.

Animals—7 nonlaminitic horses and 7 CL horses.

Procedure—In experiment 1, intradermal testing (IDT) was performed on 7 nonlaminitic and 7 CL horses to evaluate the response to a combination of 70 allergens at 15 and 30 minutes and 4 and 24 hours after injection. Three nonlaminitic and 3 CL horses used in experiment 1 were used in experiment 2 to determine whether histologic differences existed between the 2 groups. The H&E-stained tissue sections were evaluated on the basis of 3 criteria. For all analyses, 2-sample t-tests were used to determine significant differences between the groups.

Results—In experiment 1, CL horses had significantly higher total responses to IDT than nonlaminitic horses at the first 3 time periods. Also, CL horses had significantly fewer total scores of 0 than nonlaminitic horses at all time periods, except at 24 hours. In experiment 2, we did not detect significant differences between groups for any criterion.

Conclusions and Clinical Relevance—Results support the hypothesis that CL horses develop hyperreactivity to various antigenic stimuli, compared with responses for nonlaminitic horses. Therefore, the possibility that antigenic challenge may result in exacerbation of clinical signs of laminitis should be discussed with horse owners. Chronic laminitis should also be a consideration when a horse becomes lame following antigenic challenges. (Am J Vet Res 2003;64:279–283)

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in American Journal of Veterinary Research