Radial hoof strain was measured in laminitic and non-laminitic hooves. Tensile strain was found in non-laminitic hooves, consistent with the literature, but compressive strain was found in laminitic hooves close to the laminar junction, showing a change in mechanical function of hooves with this condition.
Strains during stance on the hoof wall surface have been measured by a number of authors in vitro and in vivo. Histological structure and mechanical properties vary through the wall thickness (radially); radial strain measurements may therefore aid the understanding of mechanical function of the capsule and adjacent tissues.
To develop instrumentation capable of measuring internal hoof strain, and to carry out a preliminary comparison of normal and laminitic hooves.
Six forelimbs from 4 horses, including 2 with laminitis from the same horse, were tested using an Instron test rig designed to simulate the walk at impact, midstance and breakover. Internal strains were measured at a dorsal site using strain gauges moulded into a plug made of 007 fast-set structural adhesive. In addition, kinetic and kinematic data were collected from each specimen.
When simulating the walk, a significant (P<0.0001) increase in gradient of radial tensile strain was found in a normal hoof wall, from 5.6 +/- 73.9 microstrain at the outer gauge to 418.5 +/- 170.6 microstrain at the inner gauge. However, radial strains measured at the inner gauge site in limbs with laminitis were found to be significantly (P<0.0001) compressive, with values of -406.7 +/- 156.3 and -109.9 +/- 72.4 microstrain for Specimens 1 and 2, respectively.
These preliminary data indicate that a marked redistribution may well occur in the wall of laminitic hooves. With a larger sample size, the results should have relevance to the treatment and management of laminitis.